[Source: World Health Organization, full PDF document: (LINK). Edited.]
Interim WHO surveillance recommendations for human infection with avian influenza A(H7N9) virus - As of 10 May 2013
On 31 March 2013, the first human infection with avian influenza A(H7N9) virus was reported to WHO by Chinese authorities. In the past, human infections with influenza A(H7) viruses have been associated with poultry outbreaks and resulted mainly in sporadic and mild human infections(1). Thus far, however, most reported cases with confirmed H7N9 infection have presented with pneumonia, with most of these patients being severely ill. There is currently no evidence of ongoing human-to-human transmission. In contrast to avian influenza A(H5N1), this H7N9 virus has molecular markers suggesting “low pathogenicity” in chickens; the virus appears to cause mild or no clinical disease in poultry. Although this may change over time, it will be difficult to monitor the spread of this infection among poultry, owing to the lack of visible disease.
In general, the interim surveillance guidance for H7N9 is similar to surveillance guidance for highly pathogenic avian influenza A(H5N1): http://www.who.int/influenza/surveillance_monitoring/global_surveillance_h5_guidelines_06_02_2004/en/index.html.
Interim guidance for surveillance of H7N9 is summarized below and will be updated as more information becomes available.
Objectives of surveillance
The objectives are:
- To detect human cases of H7N9 infection.
- To monitor the incidence of new cases over time and the geographical distribution.
- To detect sustained human-to-human transmission of the virus early.
Recommendations for surveillance and investigation of human infection with H7N9
For all countries
- Increase awareness among all clinicians and health care workers about the possibility of human infection with H7N9 virus and how to report cases.
- In hospital settings, clinicians should consider testing patients with severe unexplained acute respiratory disease. This should be emphasized especially if: the patient had, within two weeks of the onset of illness, a history of recent travel to an area known to have H7N9 circulating in humans or animals; or had exposure to wild or domestic animals or to environments such as markets or farms where live animals are kept or sold; or had been exposed to other individuals with recent severe respiratory illness.
- Monitor and test all clusters(2) of unexplained severe acute respiratory infections (SARI).
- Test any health care worker who develops SARI and has been caring for patients with SARI.
- Monitor existing surveillance systems for acute respiratory disease for unexpected changes in reporting or other aberrations in the data.
In addition to the above, for currently affected countries and areas bordering affected countries(3)
- In hospital settings, clinicians should strongly consider testing patients with severe unexplained acute respiratory disease.
In addition to all of the above, for currently affected countries(3)
- Monitor influenza-like illness and test selectively based on assessment of risk (i.e. contact with animals or live animal markets or occupational exposure), taking into account available capacity and infrastructure.
Testing and investigation of cases
- Information on tests for detection of H7N9 virus infections can be found at: http://www.who.int/influenza/human_animal_interface/influenza_h7n9/en/index.html
- All positive but unsubtypable specimens of influenza A should be sent immediately to a WHO Collaborating Centre for further analysis: http://www.who.int/influenza/gisrs_laboratory/collaborating_centres/en/).
- All H7N9 confirmed cases should be further investigated and close contacts monitored to detect potential human-to-human transmission and to better understand exposure risks. More detailed guidance can be found in the WHO guidelines for investigation of human cases of avian influenza A(H5N1): http://www.who.int/influenza/resources/documents/h5n1_investigations/en/index.html
- Close collaboration with the animal health sector is essential to understand the extent of the risk of human exposure and to prevent and control the spread of animal influenza.
Case definitions of confirmed and probable cases
A person with laboratory confirmation of a recent infection(4) caused by the H7N9 virus.
A person with an acute respiratory infection and clinical, radiological, or histopathological evidence of pulmonary parenchymal disease (e.g. pneumonia or Acute Respiratory Distress Syndrome [ARDS]); AND a history of close contact(5), in the two weeks before illness, with a laboratory-confirmed case of H7N9 virus infection.
Reporting of confirmed cases
Until more is known about this virus, national authorities are requested to report all confirmed cases of H7N9 within 24 hours of identification, as well as any apparent changes in patterns of transmission or severity, through the Regional Contact Point for International Health Regulations at the appropriate WHO Regional Office.
Results of ongoing surveillance activities and special studies should be communicated immediately to WHO to inform global risk assessment and guidance. In addition, national authorities are encouraged to share with WHO additional information, including onset dates, age and sex, outcome, information on the clinical spectrum of illness, underlying conditions, exposure information, travel history and treatment information. A form for the collection of detailed case-based data can be found in the Annex.
Global surveillance results
Results of human H7N9 surveillance can be found at: http://www.who.int/influenza/human_animal_interface/influenza_h7n9/en/index.html.
Current information about animal surveillance results can be found at:
(2) A “cluster” is defined as two or more persons with onset of symptoms within the same 14-day period and who are associated with a specific setting, such as a classroom, workplace, household, extended family, hospital, other residential institution, military barracks or recreational camp.
(3) For affected countries see: http://www.who.int/influenza/human_animal_interface/influenza_h7n9/Data_Reports/en/index.html
(4) Currently, the only available diagnostic test is polymerase chain reaction (PCR). However, in the future other testing, such as serology, may be available. This guidance will be updated at that time.
(5) Close contact includes anyone who provided care for the patient, including a health care worker or family member, or who had other similarly close physical contact; anyone who stayed at the same place (e.g. lived with, visited) as a probable or confirmed case while the case was symptomatic.