[Source: World Health Organization, full PDF document: (LINK). Edited.]
China—WHO Joint Mission on Human Infection with Avian Influenza A(H7N9)Virus - 18 – 24April 2013, Mission Report
On 31 March 2013, in accordance with the International Health Regulations(2005)[IHR], the Government of China reported the detection of three cases of human infection with a novel influenza A(H7N9) virus (hereafter,H7N9) in Shanghai and the province of Anhui. At the same time,the Chinese Center for Disease Control and Prevention (China CDC) posted full genome sequences of viruses isolated from the first three cases in a publicly accessible database. Overt he next two weeks additional cases were confirmed in the municipalities of Shanghai and Beijing, and in the provinces of Anhui, Jiangsu and Zhejiang. Most cases were marked by severe pneumonia and a substantial number of deaths followed. Investigations identified live bird markets as a possible source of human infection.
In response to this situation and at the invitation of the National Health and Family Planning Commission of China, a China─WHO Joint Mission on Human Infection with Avian Influenza A(H7N9) Virus was formed to assess the outbreak and provide guidance on its management (see terms of reference in Annex 3. The Joint Mission was composed of experts from China and WHO and four from Australia, Europe, Hong Kong, Special Administrative Region of China, and the United States of America. The team visited Beijing and Shanghai over 6 days, 19 – 24 April 2013, meeting with senior officials and many experts from the human and animal health sectors involved in the continuing outbreak investigation, following an agreed method of work (see Agenda in Annex 6).
Although the team was unable to visit other affected areas because of time constraints, outcomes of the extensive investigations already undertaken in China were openly shared and vigorously discussed. The team’s findings, assessment and recommendations were formed on the basis of the data available, site visits and discussions. These are presented in this report.
As of 22 April 2013, 104 confirmed cases, including 21 deaths, have been reported in Zhejiang (40 cases), Jiangsu (24),Henan (3), Anhui (3) provinces, Shanghai (33), and Beijing (1). Patients are predominantly older (median 62 years) and male (69%). Of 77 cases reported nationally for which data are available, 18 (23%)reported no identified contact with poultry; 56 (72%) reported some recent contact with live poultry and live poultry markets.
An additional case in an asymptomatic four‐year‐old boy was detected by Beijing CDC during enhanced case finding that followed the identification of the first case in Beijing.
Almost all cases have been sporadic but three family clusters have been identified. Evidence thus far is not sufficient to conclude that person‐to‐person transmission has occurred. Of more than 3000 close contacts, 19 developed respiratory symptoms. None of these symptomatic patients tested positive for H7N9 by reverse‐transcriptase polymerase chain reaction (RT‐PCR) testing. Results of serology testing are pending.
On 1 April, enhanced surveillance was introduced throughout the country for pneumonia of unknown origin and in sentinel influenza‐like illness(ILI) surveillance sites; molecular diagnostic kits were also distributed. Since then, an increase has been observed in the number of ILI consultations in ILI sites. This increase isomer likely to be related to concerns among the population than to an increase inH7N9 cases. Enhanced ILI surveillance has identified one ILI case that tested positive for H7N9 by RT‐PCR. Although it is too early to confirm the effectiveness of the closure of live bird markets in Shanghai, which took place on 6 April, no new cases have been reported there with dates of onset later than 13 April.
Areas of major uncertainty
Some important uncertainties remain, including the following:
- (1) It is unclear why severe disease has been found predominantly in older male urban residents. This pattern could be associated with behavioral factors or, as for seasonal influenza, H7N9 could be causing a larger number of mild and symptomatic infections that have gone undetected to date;
- (2) Although surveillance for pneumonia of unknown origin is routine, it is impossible to exclude the possibility that these infections have been occurring for some time;
- (3) Currently, evidence so far is not strong enough to conclude there is person‐to‐person transmission;
- (4) The extent of occurrence of unrecognized mild / asymptomatic infections is unclear and may affect estimates of case‐fatality. Persons who have mild or asymptomatic illness may not have been tested in any of the testing algorithms outlined.
Clinical features and management
The most common presenting signs and symptoms were those characteristic of influenza. Encephalopathy and conjunctivitis were uncommon, and nasal congestion and rhinorrhea were not reported as initial presentations. Common laboratory findings included normal white cell count, leukocytopenia, lymphocytopenia, thrombocytopenia, and mildly elevated liver enzymes. Most cases were severe, and a number of these rapidly deteriorated within 1 to 2 days of hospitalization to acute respiratory failure, leading to refractory hypoxemia and multiple organ failure, the major cause of death. A few mild cases were reported, especially in children.
Neuraminidase inhibitors (NAIs) were given to almost all patients but only after a median of 6 days after disease onset.
NHFPC developed a risk‐based management protocol for areas where confirmed cases are reported so that NAIs could be given earlier to symptomatic cases, even before the confirmatory result of laboratory tests for H7N9 virus.
Infection prevention and control measures in fever clinics and designated hospitals complied with national and WHO guidance.
Characteristics of avian influenza A(H7N9) viruses
The novel viruses are reassortants, comprising H7HA, N9NA and the six internal genes of H9N2 influenza A viruses. This combination of influenza genes has not previously been identified among viruses obtained from birds, humans or any other species, although individual genes are related to those of recent avian influenza viruses circulating in East Asia.
H7N9 viruses obtained from human cases, poultry and environmental samples are closely related and contain a number of genetic signatures previously associated with low pathogenicity in poultry, enhanced capacity for mammalian infection and resistance to the adamantane class of antiviral drugs. Several human H7N9 viruses were shown to be sensitive to the NAIs oseltamivir and zanamivir in vitro. It is important to note that one mammalian adaptation (E627K in the PB2 gene) occurred in many of the human H7N9 viruses but did not occur in any of the non‐human viruses. Continuing analyses are essential to improve understanding of these viruses and to detect any future changes affecting their transmissibility between humans and their pathogenicity in birds. Preliminary analyses suggest that many people lack antibodies to this virus and that production of an effective vaccine will require the selection of a new candidate H7 vaccine virus.
The detection ofH7N9 virus in live poultry markets in the vicinity of human cases in Shanghai, the contact history with live poultry or live poultry markets in a substantial number of cases, and the apparent reduction in human cases after the closure of live poultry markets in Shanghai, suggest exposure to live poultry as a key risk factor for human H7N9 infection. Although the H7N9 virus has not been detected in poultry farms so far, it is likely that they provide the source of infection, with subsequent amplification within live poultry markets leading to human infections. Although data are limited at this early stage of the investigation, it may be that the H7N9 virus is currently sustained through intra‐ and inter‐provincial trading of live poultry. If infection in poultry is not controlled the H7N9 virus may spread to additional provinces in China, leading to an even greater zoonotic threat, and thus increasing its pandemic potential. It may also facilitate the emergence of a virus that is highly pathogenic in poultry. The human and poultry viruses genetically sequenced thus far show that this H7N9 virus has adaptations that allow it to infect humans, although virological information is limited as the animal A(H7N9) test and the test strategy in China remain to be validated.
Response strategies and measures
A joint multi‐sectorial prevention and control mechanism(JPCM) has been established at national and local levels to lead and coordinate the emergency response to H7N9 virus. The national JPCM, led by the National Health and Family Planning Commission, consists of 13 governmental ministries and commissions, including the Ministry of Agriculture, the State Forestry Administration, and the Ministry of Science and Technology. An inter‐regional JPCM has also been established to support sharing of information and coordinated response among the affected provinces and municipalities, including Anhui, Jiangsu, Shanghai, and Zhejiang. Significant efforts are being made to ensure that the emergency response to the newly detected H7N9 virus is based on laws and regulations, the principle of transparency, prioritization and international collaboration. An approach based on risk assessment and evidence is being applied to inform coordinated, balanced public health interventions.
Coordinated but tailored response strategies and guidance have been provided to the different provinces based on the epidemiological situation and local needs. Early detection, early reporting, early diagnosis and early treatment ("the Four Earlys") have been the general guiding principles for the operational response.
Response measures include close collaboration between public health and animal health sectors, enhanced surveillance in humans and animals, case investigation, field investigation, risk assessment, clinical management, hospital infection prevention and control, public health interventions, risk communication, and research. Reagents for PCR detection ofH7N9 viruses in humans have been distributed to more than 400 laboratories throughout China. Several national guidelines have been issued for surveillance and epidemiological investigation, including contact tracing, laboratory testing and patient isolation and treatment.
The priority response measures have been focused on the following:
- Field investigations, including source of infection
- Enhanced surveillance in humans and animals
- Clinical management, infection prevention and control
- Risk communication
- Scientific research.
The current response at national and local levels seen by the Team has been excellent and appears to be effective. The risk assessment and evidence‐based response to H7N9 virus could serve as a model of emergency response to similar events.
Any novel influenza A virus that causes human infections is of global interest and, if disease is severe, is a cause for serious concern. After it first identified the H7N9 virus, China recognized its vital role in contributing to global public health through open channels of communication with global influenza partners and the international community.
On 31 March 2013 the China National IHR Focal Point notified WHO of the first three cases of human infection with H7N9 virus and has since made regular reports to WHO and its Member States. Regular situation updates and transparent sharing of information have demonstrated the openness of Chinese Government authorities. In addition, China CDC has shared genetic sequence data, diagnostic test protocols and viruses with the global public health and research communities. The National Avian Influenza Reference Laboratory, Harbin, has also shared genome sequences of H7N9 viruses. These actions have contributed greatly to the global risk assessment and response, including the selection and development of candidate human H7N9 vaccine viruses and vaccine potency and diagnostic reagents, as well as a better understanding of antigenicity, pathogenicity and transmissibility of the virus.
The National Health and Family Planning Commission has maintained close technical collaboration with WHO staff through China CDC. As a newly designated WHO Collaborating Centre for Reference and Research on Influenza, the National Influenza Centre in China has maintained regular communication and technical discussions with other WHO Collaborating Centres for influenza. As a member of the Global Outbreak Alert and Response Network (GOARN), China CDC provided a situation update to GOARN partners.
In summary, China’s transparent and timely sharing of technical information, data and viruses is greatly appreciated and has contributed immensely to current global understanding of the H7N9 virus, risk assessment and actions required to manage the shared risk.
In March 2013, China identified three human infections by an avian influenza A(H7N9) virus.
This virus had never been known to infect people before. China responded quickly including by establishing a joint multi‐sectorial coordination mechanism, initiating several investigations, notifying WHO under the International Health Regulations 2005), posting sequences of the virus, sharing viruses with the WHO Influenza Collaborating Centers and other laboratories and mounting effective countermeasures such as closure of live poultry markets in some locations. The response has demonstrated that health authorities were well prepared and acted quickly, effectively and professionally.
Since then, this virus has caused over 100 human infections. Most of these infections have led to severe disease, including more than 20 deaths.
Currently, evidence so far is not strong enough to conclude there is person‐to‐person transmission. The limited available information suggests that many infections caused by this virus may be related to exposure to infected poultry in live poultry markets or to environments contaminated by this virus.
However, future studies can strengthen the evidence.
The risk to people posed by the emergence of the H7N9 virus must be considered unusually serious, for several reasons. First, this virus has caused serious disease, including death, in some people. Second,this virus does not appear to cause disease in poultry (although it could change in the future to become highly pathogenic) and therefore could spread silently. Third, this virus has caused more human infections and disease in a shorter period of time than any other known avian influenza virus.
Fourth, some H7N9 viruses show genetic changes that suggest they are partially adapted to infect humans more easily than other avian influenza viruses. Taken together,these findings suggest that the possibility of this virus becoming transmissible among people is higher than for any other known avian influenza virus and therefore it must not be ignored.
On the basis of this assessment, the Joint Mission has made seven high‐level recommendations to the Government of China, as below.
- Undertake intense and focused investigations to determine the source(s) of human H7N9 infections. Identification of the source will enable urgent action to prevent continuing virus spread, with its potentially severe consequences for human and animal health.
- Maintain a high level of alert, preparedness and response even though human cases might drop in the summer (ast hey do for many other avian influenza viruses) because of the seriousness of the risk posed by this virus and because much basic information remains unknown.
- Continue to conduct and strengthen both epidemiological and laboratory‐based surveillance in human and animals in all provinces of China to identify changes that might indicate the virus is spreading geographically and gaining the ability to infect people more easily or transmit efficiently from person to person.
- Ensure frequent mutual sharing of information, close and timely communication and, when appropriate, coordinated or joint investigations and research among ministries of health, agriculture and forestry because this threat requires the combined efforts of all these sectors.
- Continue high‐level scientific collaboration, communication and sharing of sequence data and viruses with WHO and international partners because the threat of H7N9 is also an international shared risk and concern.
- Encourage and foster the scientific and epidemiological studies and research needed to close major gaps in critical knowledge and understanding.
- Continue preparedness planning and other IHR core capacity strengthening work because such investments make a major difference in readiness to address health security risks and emergencies, including H7N9.
Annex 1 –Detailed Findings
Data as of 23 April 2013
The first cases of infection with novel avian influenza A(H7N9) were a father and son pair in Minhang District, Shanghai. They both had disease onset dates of 19 February 2013, initially presenting with influenza‐like illness, which rapidly progressed to pneumonia. A second son had previously been hospitalised with pneumonia. Concerned by these three cases, clinicians immediately alerted public health authorities. Four more patients with similar symptoms were admitted to the same hospital in Shanghai in late February and early March.
Specimens from the father and an unrelated case with onset date of 27 February 2013 were positive for influenza A but unsubtypable: hence, specimens were referred to the WHO Influenza Collaborating Centre at the Chinese CDC (see timeline). A third similar influenza A unsubtypable case was reported to the Chinese CDC from neighbouring Anhui Province. The isolates from all three were very similar novel reassortant avian influenza viruses. Therefore, on 31 March the Chinese authorities notified them to WHO under the IHR.
Diagnostic test kits were distributed to laboratories across the country beginning 1 April. As of 22 April 104 confirmed cases have been reported in five adjoining Chinese Provinces, plus Beijing, with 54 counties/district involved. The affected areas include Zhejiang (40 cases), Shanghai (33), Jiangsu (24), Henan (3), Anhui (3) and Beijing (1). An additional case in an asymptomatic 4‐year‐old boy was also detected by Beijing CDC during enhanced surveillance for those who had the same exposure to potentially infected poultry and the environment.
As of 22 April the virus has not been detected in the other 25 provinces in China despite ongoing routine sentinel ILI surveillance, increasing numbers of persons seeking testing and enhanced surveillance for pneumonia with unknown aetiology. Eighty‐three per cent of cases were reported to be urban residents.
Of reported cases, three have been mild, 21 cases(20%) are known to have died and 13 cases are known to have been discharged from hospital. There were more than twice as many males as females( 69% vs. 31%), with a median age of 62 (range 2‐89 years).
Generally, the age pattern was considerably older and far more male dominated than was observed in China for A(H5N1) (Figure 1). Child cases discovered were either mild or asymptomatic. Many more H7N9 cases had been confirmed over four weeks than had been confirmed and reported for A(H5N1) in China over ten years (Figure 1), Examination of risk factors showed the prevalence of chronic ill health that would be expected in such an older population. An association with contact with animals and in particular live poultry was observed.
Of 77 cases reported nationally for which data were available, only 18 cases (23%) reported no contact with animals and 56 (72%) reported some recent contact with live poultry. In the 33 Shanghai cases, after detailed questioning only 2 cases reported no exposure of any kind to poultry.
However, an unknown factor is the frequency of such exposure in an older population living in urban areas where visits to live bird markets (so‐called wet markets) are common. The incubation period is estimated to be approximately 7 days by calculating the median number of days from exposure to poultry or live poultry markets to illness onset, both for confirmed cases with clear multiple exposures and for those with a single exposure.
The cases occurred mainly as sporadic incidents, with only three small clusters of two and three cases. Intensive case finding among 3000 contacts found 19 persons with respiratory symptoms, including 14 health care workers but none of these were positive for H7N9 by the new specific PCR test. Currently, evidence so far is not strong enough to conclude there is person‐to‐person transmission. The occurrence of asymptomatic and milder cases could not be excluded as serological testing is awaited.
Results of interventions
After declaration of the outbreak by national authorities on 31 March, alerting of populations to seek care and intensified surveillance by a number of regions, sentinel sites for ILI reported a significant rise in the number of consultations.
However, virtually no new H7N9 cases were detected at these sites. For example, in Shanghai Municipality, although some influenza A(H1N1) cases were detected, no new unsubtypable influenza A infections were seen.
Because of the association with exposure to poultry and, in particular, live bird markets, three provinces with the largest number of cases closed large live bird markets in some cities. Closure was followed by a substantial drop in the numbers of new cases reported to authorities, though two incubation periods have yet to be passed (Figure 3).
Areas of major uncertainty
At this time a number of important uncertainties remain. These include the following:
- Why severe disease occurs predominantly in older male urban residents is not clear. It could be that behavioural factors and exposure to live birds in wet markets increased the risk of infection. Alternatively, it could be that they represent only a proportion of a much larger number of mild and symptomatic infections and disease progression is mainly observed in the most vulnerable population, as is the case for seasonal influenza (Figure 4). However, a problem with this hypothesis how to explain the gender imbalance.
- Similarly, it remains to be determined whether the predominance of exposure to live poultry in the cases is in fact a risk factor or simply the norm in the older male urban populations where these infections occur.
- Although active surveillance for pneumonia of unknown aetiology is routine, the possibility cannot be excluded that these infections have been occurring for some time.
Clinical features and management
As of 16 April, a total of 77 confirmed cases were reported in six provinces and municipalities, among whom 67 had sufficient clinical data to analyse. The outcomes of these patients as of 22 April were 14 deaths and 9 discharges; the remaining 44 patients were still hospitalized. In some cases hospitalization was for infection control considerations rather than active treatment.
The median age of the patients was 63 years (range 4 to 87), and two‐thirds were male.
Comorbidities would be expected in this age and gender group; about 60% of the patients had comorbidities such as coronary heart disease, diabetes, hypertension, and chronic obstructive pulmonary disease.
These included fever, cough,shortness of breath, fatigue,muscle aches, hemoptysis, and gastrointestinal symptoms(Figure 5). Signs such as encephalopathy (n = 2) and conjunctivitis (n = 1) were uncommon.
Nasal congestion and rhinorrhoea were not reported as initial symptoms.
Mild cases were described, all in children and often manifested as fever only. In comparison, some adult patients had rapid progression to bilateral pulmonary infiltrates, often leading to severe hypoxemia within 1 to 2 days.
These included normal white cell count, leukocytopenia, lymphocytopenia, thrombocytopenia, and mildly elevated liver enzymes.
A National Practice Guideline for Clinical Management of Avian Influenza A(H7N9) Infection was issued by the NHFPC on 2 April, and revised on 10 April. In most cases, initial treatment complied with the recommendations of these guidelines.
Specifically, NAIs were given to almost all patients but only after a median of 6 days (range 0 to 23) after disease onset.
Medical complications and their treatment
About two‐thirds of cases developed severe pneumonia and required ventilatory support in intensive care units.
Other complications included shock, acute renal failure, and barotrauma. Some patients with severe hypoxemia responded poorly to conventional mechanical ventilation, which necessitated advanced supportive therapy, such as high‐frequency oscillation ventilation (HFOV) and ECMO. Refractory hypoxemia and multiple organ failure were the leading causes of death. Lymphocytopenia and organ failure, rather than age,sex, or comorbidities, appeared to be risk factors for mortality in hospital.
Patients treated with NAIs within three days appeared to have had better clinical outcomes than other patients. More than 60% of patients received intravenous corticosteroids in an initial daily dose equivalent to 100mg hydrocortisone (range 25 to 300mg).
Patient handling and infection control
A risk‐based protocol was developed in national practice guidelines to support early antiviral therapy in suspected cases (Table). In addition, training materials for epidemiology, clinical manifestation, diagnostic specimen collection, and diagnosis and treatment were distributed to all hospitals in affected areas. The planned referral system in these areas was such that, for every suspected case, respiratory specimen testing using PCR would be completed at the local Center for Disease Control and Prevention within 6 to 8 hours. All confirmed cases, except those whose severe condition did not permit transportation, were then transferred to designated hospitals. Close contacts were closely monitored under medical observation, with NAIs prescribed only after onset of clinical symptoms. Among the 2033 close contacts, no confirmed cases were reported as of 22 April.
In general, infection prevention and control measures in fever clinics and designated hospitals complied with national and WHO guidance. Apart from hand hygiene, different types of personal protective equipment (PPE) were reported to have been used during the care of suspected and confirmed cases. Intense surveillance was undertaken in healthcare workers exposed to cases, and there were no reported infections among healthcare workers.
Table. Indications for early antiviral therapy*
- Confirmed case with avian influenza A(H7N9) infection
- ILI case testing positive by influenza A rapid antigen test
- ILI case testing negative by influenza A rapid antigen test or without access to influenza A antigen test, who meets any of the following criteria:
- Close contact (including healthcare workers)
- One of the cluster cases
- Recent exposure to poultry (within one week)
- Significant comorbidities, such as chronic cardiopulmonary diseases, advanced age, or pregnancy
- Rapid progression that merits antiviral therapy as judged by treating physician
- Pneumonia of unknown cause
* From National Practice Guidelines on Clinical Management of Avian Influenza A(H7N9) Infection. ILI, influenza‐like illness
Severe cases deteriorated rapidly, within 1 to 2 days, leading to refractory hypoxemia and multiple organ failure, which were the major causes of death.
Mild cases were reported,though there were few
NHFPC developed a diagnostic and treatment protocol for human infection with avian influenza A(H7N9) virus for areas where confirmed cases were reported such that NAIs could be given earlier, even before confirmation by laboratory testing for H7N9 virus.
Characteristics of the avian influenza A(H7N9) viruses
The preliminary analysis of the first cases by the Shanghai Public Health Clinical Center and the Shanghai CDC, followed by the isolation and full genome sequencing of three viruses (A/Shanghai/1/2013, A/Shanghai/2/2013 and A/Anhui/1/2013) by China CDC, were critically important steps in the management of the outbreak. Immediate posting of the sequences in the publicly accessible GISAID database and rapid sharing of viruses by China CDC have enabled Chinese and international scientists to begin analyzing the viruses at the earliest possible stage.
Analyses of the first three isolates showed that the viruses were reassortants comprising H7 HA, N9NA and the six internal genes of H9N2 influenza A viruses. This gene constellation had not been identified previously among viruses obtained from birds, humans or any other species. While all three viruses were closely related, A/Shanghai/2/2013 and A/Anhui/1/2013 were more similar to each other across all 8 gene segments than to A/Shanghai/1/2013, which was distinct at multiple sites. Comparisons with other influenza A virus sequences in public databases showed that the most closely related viruses were recent low‐pathogenic Eurasian H7N3 viruses (e.g., A/duck/Zhejiang/12/2011(H7N3)), Eurasian H7N9 (egg, A/wild bird/Korea/A14/2011(H7N9)) and H9N2 viruses (e.g., A/brambling/Beijing/16/2012(H9N2)).
The first three isolates contained a number of genetic signatures previously associated in other subtypes with low pathogenicity in poultry, enhanced capacity for mammalian infection, resistance to the adamantane class of antiviral drugs and sensitivity to the neuraminidase inhibitors oseltamivir and zanamivir. These signatures include the following:
- A single arginine at the HA cleavage site, consistent with low pathogenicity in poultry;
- Deletion of five amino acids in the NA stalk, associated with adaptation to poultry;
- Q226L substitution in the HA, associated with enhanced binding to the α‐2,6‐linked sialylated receptors found in the mammalian respiratory tract;
- E627K in the PB2 protein, associated with viral replication at the lower temperature of the mammalian respiratory tract;
- S31N in the M2 protein, conferring resistance to adamantanes;
- Absence of the H275Y substitution in the NA, associated with resistance to the oseltamivir in H1N1 viruses;
- R292K in one virus (A/Shanghai/1/2013), associated with markedly reduced sensitivity to oseltamivir and modestly reduced sensitivity to zanamivir.
In vitro analyses confirmed that all three viruses bound both α ‐2,3‐ and α ‐2,6 linked sialic acids, suggesting an ability to bind to both avian and mammalian cells. In functional assays, all three isolates were sensitive to both NAIs. In the case of A/Shanghai/1/2013, this result appears to reflect the presence of a mixture of viruses with R or K at position 292 of the NA.
All three viruses could be propagated readily in embryonated hen’s eggs and human, canine and porcine cell lines. Pathogenicity studies in birds or animals have not yet been performed but these and comprehensive antigenic analyses will begin soon.
It is expected that production of an effective vaccine against the new H7N9 viruses will require the development of a new candidate vaccine virus.
Further isolates and full or partial genome sequences have since been obtained by several laboratories. These isolates were from other human cases and from poultry and environmental samples taken from live poultry markets or other locations in Shanghai, Jiangsu, Zhejiang and Beijing, including many samples analysed by the National Avian Influenza Reference Laboratory, Harbin. Some of these sequences have been posted in the GISAID database. These viruses have provided important additional information on the diversity of H7N9 viruses currently circulating in eastern China. For example:
- Viruses isolated from humans, avian species and environmental samples are closely related;
- All lack a multi‐basic amino acid cleavage site in the HA;
- Most but not all human isolates have 226L in the HA;
- Only some human isolates have 627K in PB2; all tested avian and environmental isolates have 627E in PB2;
- All apart from A/Shanghai/1/2013 have R292 in the NA;
- All those tested to date are susceptible to oseltamivir and zanamivir in vitro.
Development and availability of human diagnostic and serological assays
Between 2 and 13 April (see timeline), real‐time PCR primers and probes based on the sequences of the first three virus isolates were distributed by China CDC to more than 400 surveillance and other diagnostic laboratories throughout China.
Protocols, along with primer and probe sequences, were posted on the WHO website. All PCR‐confirmed human cases have been diagnosed using these reagents.
Preliminary human serological assays have been undertaken using antigens from A/Anhui/1/2013, with early data indicating that sera from children, adults and the elderly lack antibodies to this virus before and after immunization with 2012–2013 seasonal influenza vaccine. This assay was used to detect antibodies in convalescent serum from two patients. Assays of avian serum samples to date have used A(H7N2) antigens and antisera (see section on animal health). Full development of H7N9‐specific serological assays for human and animal use awaits the availability of specific post‐infection antisera raised against H7N9 viruses in ferrets or chickens.
In response to the detection of H7N9 human infections, agricultural authorities have as of 22 April sampled 2582 live bird markets, 8798 poultry farms, 337 poultry slaughter houses, 341 wild bird habitats, 227 pig slaughter houses and 633 environmental sites. A total of 218,344 samples from22 provinces have been tested. These samples were collected from three surveillance zones. The first zone comprises the four Chinese Provinces Zhejiang, Jiangsu, Henan, and Anhui, plus the municipalities of Shanghai and Beijing, from which 122,344 samples have been tested; the second comprises those provinces adjacent to the affected provinces from which 38,759 samples have been tested; and the third comprises the other provinces, from which 57,039 samples have been tested.
The swab samples (both oro‐pharyngeal and cloacal) were tested in provincial laboratories by real‐time PCR using H7 Eurasian lineage HA primers; positives were confirmed by virus isolation at the National Avian Influenza Reference Laboratory,Harbin. Blood samples were tested using a low pathogenic H7N2 virus antigen and a corresponding positive control antiserum provided by the National Avian Influenza Reference Laboratory, Harbin.
Preliminary data suggest that this antigen will detect antibody raised against the recent H7N9 virus. Of these, 39 positive swab samples from live bird markets were identified by virus isolation: 20 in Shanghai, 12 in Jiangsu,six in Zhejiang and one in Anhui.
One additional specimen from a wild pigeon in Nanjing,Jiangsu Province, was also positive.
No positive serum samples were detected.
As a result of targeted investigation of the source of infection for the first confirmed H7N9 case and suspected family cluster in Shanghai, environmental samples from a poultry market frequented by these family members tested positive for H7N9 by PCR. Further, poultry in four other live poultry markets within 1.5 km of the residence of the infected cases were found to be infected with H7N9.
Following the H7N9 outbreak,surveillance in wild birds was also enhanced nationally but no H7N9‐positive samples from wild birds or their environments have been detected thus far.
H7N9 viruses were detected in live bird markets in 3 provinces (Anhui,Jiangsu and Zhejiang) and one municipality (Shanghai).
Environmental samples collected from a poultry market frequented by the members of the family cluster in Shanghai had evidence of extensive contamination byH7 virus RNA.
It appears that the closure of live poultry markets in Shanghai was associated with a reduction in the number of new human cases, although a causal relationship should not be inferred and a definitive conclusion cannot be drawn at this time (see Epidemiology section and Figure 3).
Taken together with contact history with live poultry/live poultry markets in a substantial number of cases,these findings support a key role for exposure to live poultry as a risk factor for humanH7N9 infection.
Viruses have not been detected in poultry farms thus far. For example, in Shanghai, viruses have not been detected in the local farms that supply Shanghai live bird markets.However, 75% of the Shanghai poultry supply comes from adjacent provinces where the virus source has not been identified (as of 21 April). AlthoughH7N9 viruses have not been detected in poultry farms, it is well recognized that avian influenza is amplified and maintained in live poultry markets. It is possible therefore that a small number of infected farms could explain the level of infection in live bird markets.Given the number and severity ofH7N9 human infections it is critical to identify the source(s) ofH7N9‐infected poultry so that appropriate interventions can take place. The extensive surveillance in farms so far is still likely to be insufficient to detect small numbers of farms that may be infected withH7N9 virus at low prevalence rates.
Eleven human virus isolates and 39 poultry/environmental isolates have been genetically sequenced thus far at the China CDC and the National Avian Influenza Reference Laboratory, Harbin,respectively. The majority of the sequenced isolates from both humans and poultry/environment have the amino acid 226L in the haemagglutinin gene, which is known to confer enhanced binding to the α 2‐6‐ linked sialic acid receptors found in human upper airways. It is notable that none of the 39 viruses isolated from poultry have the mammalian adaptation marker PB2 627K while over half of the human virus isolates do. Adaptation within infected humans may explain this observation; however, other possibilities cannot be excluded at this time.
Although data at this early stage of the investigation are limited, it appearsthattheH7N9 virus is currently sustained through intra‐ and inter‐provincial trading of live poultry. If infection in poultry is not controlled,the virus may spread to additional provinces in China.
Such a situation would lead to an even greater zoonotic threat, and thus increase its pandemic potential. Continued circulation of a low pathogenicH7 virus in poultry also poses the risk of the emergence of a virus that is highly pathogenic in poultry.
Initial conclusions based on combined epidemiological, clinical, virological and animal health information
The data are most consistent with an avian influenza virus that is considerably more transmissible to humans than any earlier avian influenza virus known to date. This H7N9 influenza virus is also the first reported low pathogenic A(H7) avian influenz
virus of any subtype that has caused severe disease in humans.
Evidence so far is not sufficient conclude there is person‐to‐person transmission.
Moreover, no sustained person‐to‐person transmission has been found.
The reasons for the unusual age and gender distribution of the human cases are unknown and demand deeper investigation. This would include seroepidemiological studies to determine whether there have been larger numbers of mild and asymptomatic infections than have thus far been recognized.
The virological adaptations to mammalian hosts are particularly concerning but they need to be studied in combination with clinical and epidemiological data rather than in isolation.
Response strategies and measures
Leadership, command and coordination
In line with the national and local pandemic influenza preparedness and response plans, a joint multi-‐sectorial prevention and control mechanism(JPCM) has been established at national and local levels to lead and coordinate the emergency response to theH7N9 virus.
The national JPCM, led by the National Health and Family Planning Commission, consists of 13 governmental ministries and commissions, including the Ministry of Agriculture,the State Forestry Administration, and the Ministry of Science and Technology. An inter‐regional JPCM has also been established to support sharing of information and coordinated response among the affected provinces, including Anhui,Jiangsu, Shanghai, and Zhejiang.
Significant efforts are being made to ensure that the emergency response to the newly detectedH7N9 virus is based on laws and regulations,the principle of transparency, prioritization and international collaboration. An approach based on risk assessment and evidence is being applied to inform coordinated, balanced public health interventions.
Different response strategies and guidance have been provided to the different provinces based on the epidemiological situation and local needs. Early detection, early reporting, early diagnosis and early treatment("the Four Earlys") have been the general guiding principles for the operational response.
Response measures include close collaboration between public health and animal health sectors, enhanced surveillance in humans and animals, field investigation,risk assessment, clinical management, hospital infection prevention and control, public health interventions, risk communication, and research. Several technical guidance documents have been issued for surveillance and epidemiological investigation including contact tracing, laboratory testing and patient isolation and treatment.
The priority response measures have been focused on the following:
- Field investigations, including source of infection
- Field investigations on all confirmed cases, including contact tracing, have been conducted by local CDCs with the support from China CDC. The National Influenza Centre at China CDC, which is also a WHO Collaborating Centre of the Global Influenza Surveillance and Response System(GISRS), isolated and sequenced the full genomes of the firstthreeH7N9 viruses from humans and shared, at the earliest possible moment,the gene sequences through the publicly accessible database GISAID.Genome sequences of three A(H7N9) viruses from birds and environment were also uploaded to GISAID by China Avian Influenza Reference Laboratory in Harbin, China.
- Based on the preliminary findings that the virus was an avian virus,the Ministry of Agriculture classified A(H7N9) as first class at interim for animal surveillance and notification, and with other ministries enhanced joint surveillance in poultry farms and live bird markets(so‐called wet markets). In some cities where human cases were occurring live bird markets were closed temporarily.
- In Shanghai,studies have been developed through collaboration between the Shanghai CDC, Shanghai Animal Institute)the Shanghai Bureau of Industry and Commence and the Forestry Commission under the Joint Investigation Structure to find the source of human infection.
- Enhanced surveillance in humans and animals
- The national surveillance network was alerted and surveillance was enhanced. In addition to the routine IL surveillance, emphasis was placed on enhancing surveillance for pneumonia of unknown origin and severe acute respiratory infections. Surveillance data are being reported in a timely manner to provincial authorities and to China CDC for risk assessment and response. As part of the global WHOGISRS,the CNIC, in addition to uploading sequences of the whole genome of the first three novelH7N9 viruses, has contributed significantly to global alert and surveillance activities. These contributions include the PCR protocol for virus detection and virus isolates to enable WHO Collaborating Centers and Essential Regulatory Laboratories to select and develop vaccine viruses, vaccine reagents and diagnostic reagent kits, and to conduct further characterization of the virus, e.g. pathogenicity and transmissibility. China CDC published its findings in the New England Journal of Medicine within 15 days.
- Diagnostic kits were developed by the CNIC based on PCR technology. Reagent kits were distributed to all provincial CDCs, and to all prefecture/city CDC in affected provinces within 48 hours. Reagent kits have been sent to all CDC laboratories at provincial, prefecture and city levels, and military and border‐control laboratories in China.
- Surveillance forH7N9 has been initiated in animals, including poultry, pigeons, and ducks by virus or antibody detection. WhereH7N9 viruses were detected in markets, backward source tracing was undertaken to determine the source farms of the poultry, and additional specimens were collected from the source(s)for analysis.
- Clinical management, infection prevention and control
- Fever clinics were activated in health care facilities for screening of patients and to ensure appropriate infection prevention and control and clinical management.National guidance onH7N9 case management was issued.Hospitals, with infection control recommendations strictly implemented, were designated specifically tomanageH7N9 cases. In Shanghai the Municipal Public Health Clinical Centre, which has 500 beds and hosts high‐level expertise in clinical management, has hospitalized and managed suspected cases, and accumulated report Page 30 valuable experience in managing and treating patients with a disease associated with a new virus. The Chinese government is providing free clinical care for allH7N9 patients.
- At national level, expertise was absorbed into groups for case management, in particular for severe cases, and information was dispatched nationwide whenever there was a need. The Chinese regulatory agency,the China Food and Drug Administration (CFDA), accelerated the regulatory process and has approved Peramivir, an injectable NAI, for treatment. National stockpiles of Oseltamivir and Zanamivir were also reviewed and renewed. Medical supplies have also been ensured.
- Risk communication
- Epidemiological and virological findings were shared in a timely and transparent manner with WHO,the Food and Agriculture Organisation of the United Nations(FAO) and the World Organization for Animal Health (OIE). Continuous information was supplied through the International Health Regulations(IHR)system and was posted on the WHO website; formal notifications were made of outbreaks in poultry through the OIE system.
- Updates on surveillance and risk assessment were shared with the public in a timely manner in collaboration with media at national and local levels.
- Regular press releases were made to the public by local and national governments, especially by the health authorities,to provide timely updates on theH7N9 situation and to address public concerns.
- Health education activities are being implemented to advise about health risks ofH7N9 and to promote good hygiene practices, including hand washing, cough etiquette and safe handling of food.
- Scientific research
- Under the overall coordination of JPCM, a research programme has been developed with the Ministry of Science and Technology as the lead agency to better understand the virus and disease, including the source of infection, antigenicity, pathogenicity and transmissibility ofH7N9, and to develop and evaluate interventions, including pharmaceutical and non‐pharmaceutical measures.
- Response at national and local levels has been excellent and appears to be effective.
- The risk assessment and evidence‐based response toH7N9 virus could serve as a model of emergency response to similar events.
- International collaboration
- Any human infection with a new subtype of influenza virus, especially one causing severe disease, is of global interest and serious concern. After it first identified theH7N9 virus, China, in addition to fulfilling its obligations in timely notification under the IHR, has recognized its vital role in contributing to global public health work through open channels of communication with global influenza partners and the international community. Event reporting and information sharing with the international community The China National IHR Focal Point notified WHO of the first three cases of human infection withH7N9 on 31 March 2013. The outbreak is considered an event that may constitute a potential Public Health Emergency of International Concern. Since then,regular reporting has been made to WHO through the WHOIHR Contact Point for the Western Pacific Region, and updated information has been shared with all WHO Member States through the Event Information Site, which is open to all the National IHR Focal Points.
- Other channels of communication include regular updates on the NHFPC website, as well as on WHO websites at Country, Regional, and Headquarters level, including through Disease Outbreak News(DON).
- Given strong interest from the public and the media, and to address concerns about this new virus, joint NHFPC‐WHO press briefings were convened, including the first such press conference with WHO Country Office on 8 April 2013,to supplement individual press contacts with both offices. These situation updates and transparent sharing of information demonstrated Chinese collaboration with WHO and the openness of Government authorities, and was widely disseminated by more than 75media representatives.
- Sharing of virus and information
- The whole genome sequences of the first three human cases were uploaded by the National Influenza Centre, which is also a WHOCC for Reference and Research on Influenza,to the GISAID as quickly as possible for public access.Genome sequences ofthreeH7N9 viruses from birds and the environment were also uploaded to GISAID by the national avian influenza reference laboratory in Harbin in China. This has contributed significantly to global risk assessment and risk response, and promoted the spirit of the Pandemic Influenza Preparedness(PIP) Framework. AstheH7N9 viruses are defined as PIP Biological Materials under the PIP Framework,their distribution is covered by the principle of sharing of benefits arising from their use according to public health risk and need.
- The WHOCC in Beijing has undertaken timely sharing of virus isolates with other WHOCCs for influenza and WHO Essential Regulatory Laboratories of GISRS. Thus far, all six WHOCCs and four WHO Essential Regulatory Laboratories of GISRS have receivedH7N9 virus isolates from the WHOCC in Beijing. In addition,the virus has been shared with laboratories in Taiwan and Hong Kong SAR, WHOH5 Reference Laboratories, and other requesters. As of 22 April, 15 shipments have been made to 13 recipients, including GISRS laboratories and other entities such as vaccine manufacturers. This is a significant contribution to the global risk response and will lead to the selection and development ofH7N9 candidate vaccine viruses, potency reagents, PCR reagent kits and diagnostic protocols, as well as better understanding of antigenicity, pathogenicity and transmissibility ofH7N9.
- Technical collaboration
- The NHFPC,through the Chinese CDC, quickly established and has maintained very close technical collaboration with WHO staff, with daily discussions at country level, and frequentconsultation involving all three levels of WHO: Country Office, Western Pacific Regional Office and WHO Headquarters. As a newly designated WHO Collaborating Center for Reference and Research on Influenza,the National Influenza Center in China has maintained close and regular communication and technical consultation with other WHOCollaborating Centers for Reference and Research on Influenza. The Chinese CDC, as as member of the Global Alert and Response Network (GOARN), also provided a situation update to the GOARN Steering Committee members. Bi‐lateral collaboration is also ongoing, including sharing of information and technical collaboration with US CDC, Canada Public Health Agency, ECDC,NIID and Korean CDC In the second week of April,the NHFPC formally invited WHO to identify technical experts to join a China‐WHO joing mission on human infection with avian influenza A(H7N9) virus. The on‐site mission was conducted in Beijing and Shanghai 19‐24 April o understand the nature of the outbreak, investigate the prevention and control measures already taken by the Chinese Government, assess the outbreak situation and public health risks, and to provide recommendations on future prevention and control measures, and priority areas for specific research,resulting in this report.
- International collaborative efforts, especially transparent and timely sharing of information and viruses, as well as technical level discussions and consultations convened by China in the response toH7N9 are highly appreciated and well recognized by the international community.
- The collective efforts by China and the international community in line with the IHR and other international and regional frameworks have greatly contributed to our current understanding about the nature oftheH7N9 virus, public health risk assessments and actions required to manage the shared risk.