10 Jul 2013

Influenza Update N° 189, 5 July 2013 (WHO, July 10 2013, edited)

[Source: World Health Organization, full PDF document: (LINK). Edited.]

Influenza Update N° 189, 5 July 2013

 

Summary

  • Influenza activity in the northern hemisphere temperate zones remained at inter-seasonal levels.
  • In most regions of tropical Asia influenza activity decreased, except for Sri Lanka and Viet Nam where influenza A activity remained relatively high.
  • In Central America and the Caribbean, influenza activity remained low or similar compared to previous weeks, except in Cuba and the Dominican Republic where high influenza activity was reported and in Costa Rica, El Salvador and Panama, where influenza activity began to increase.
  • Influenza activity in the southern hemisphere increased considerably in South America and in Southern Africa but remained low in Oceania. In South America, respiratory syncytial virus remained the predominant circulating virus, but the proportion of influenza positive viruses continued to increase.
  • As of 5 July, a total of 133 cases of H7N9 have been reported from China (132 from China’s National Health Family and Commission, and 1 from Taipei Centers for Disease Control) including 43 deaths. More and updated information will be posted at: http://who.int/influenza/human_animal_interface/influenza_h7n9/en/index.html

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Countries in the temperate zone of the northern hemisphere

North America

Overall influenza activity in North America has continued to decrease to low levels throughout most of the region.

In Canada, the percentage of positive influenza tests continued to decline, with 1.1% testing positive in the second week in June. The national influenza-like-illness (ILI) consultation rate has remained stable during the last ten weeks, but was still above the expected range for the past seven weeks which was most likely due to rhinovirus.

In the United States of America (USA), influenza activity remained low and at inter-seasonal levels. Nationally, the proportion of ILI outpatient consultations decreased to 0.8%, below the national baseline of 2.2%.

Of 1925 specimens tested since 16 June, 3.5% were positive for influenza, which showed a decrease from the previous week.

The USA recently reported four human infections with influenza A(H3N2)v virus. For more details see http://www.cdc.gov/flu/spotlights/h3n2v-firstcases-2013.htm.

Mexico has reported relatively stable influenza activity over the last few weeks with the majority being influenza A. From the last week in May to the third week of June, 7.6% of specimens tested positive for influenza. Among the positive specimens, 51.5% of those were influenza A(H3N2) and 39.4% were A(H1N1)pmd09. Acute respiratory infection (ARI) cases increased slightly while the number of pneumonia cases decreased from the previous week, but both have shown decreasing trends overall.

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Europe

Influenza activity in Europe remained at inter-seasonal levels. Consultation rates for ILI and ARI were at low levels for all countries in the region. None of the specimens collected from sentinel sites tested positive for influenza. Of the 231 influenza virus detections reported since 20 May, 55% were characterized as influenza B.

 

Northern Africa and the Western Asia region

Influenza activity is low in Northern Africa and in Western Asia region. Influenza A(H1N1)pdm09 have mainly been detected throughout the season in most countries in the western Asia region, with the exception of Jordan which reported a majority of influenza B.

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Northern Asia

Influenza activity in much of the temperate region of Asia has decreased gradually over the past several weeks and is coming to inter-seasonal levels.

In China, as of 5 July 2013, 133 cases of influenza A(H7N9) have been identified, of which 43 have died, more and updated information is posted at: http://who.int/influenza/human_animal_interface/influenza_h7n9/en/index.html

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Countries in the tropical zone

Tropical countries of the Americas/Central America and the Caribbean

In both the Caribbean and Central America, influenza activity remained low and or similar compared to previous weeks, except in Cuba and the Dominican Republic where high influenza A(H1N1)pmd09 activity continued to be reported, in Costa Rica where increased influenza A(H1N1)pmd09 activity was reported, and in El Salvador and Panama where increased influenza A(H3N2) was reported.

Influenza activity in Cuba remained high, with 35.3% of 604 specimens testing positive for influenza viruses since the end of May. Of those that were positive for influenza A, 86.8% were influenza A(H1N1)pmd09 and 13.2% were influenza A(H3N2). Rhinovirus and Para-influenza continued to circulate in Cuba.

Influenza activity also remained high in the Dominican Republic. Out of 166 samples tested, the proportion testing positive for influenza increased from 14.6% six weeks ago to 45.9% in the most current week, with influenza A(H1N1)pmd09 being the most detected virus.

Costa Rica reported increasing influenza activity, with the percent of positive influenza viruses increasing from 5% at the end of May to 42% in the current week. Influenza A(H1N1)pmd09 is the main circulating virus.

El Salvador and Panama also reported increasing influenza activity, with A(H3N2) constituting 100% of positive influenza samples in both countries for the past three weeks.

In tropical South America, ARI activity remained at same levels except in Colombia, Brazil and Venezuela , where activity seemed to increase.

In Colombia, the proportion of SARI hospitalizations and SARI ICU admissions continued to increase compared to the previous weeks. Of the 125 specimens analyzed in the past two weeks, 31% tested positive for all respiratory viruses. Twenty-eight percent of those that tested positive for all respiratory viruses were influenza A(H1N1)pmd09.

Venezuela reported increased ARI activity above the epidemic threshold for this time of year and the trend for reported pneumonia cases also increased in the last few weeks. Of the samples that were positive for influenza, 90.8% were due to influenza A(H1N1)pdm09 followed by influenza A(H3N2).

Brazil reported increasing trends of ILI and SARI cases, associated with co-circulation of influenza A(H1N1)pmd09 and Influenza B.

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Central African tropical region

Many countries in the Central African tropical region reported low activity, with the exception of Cameroon, Cote d’Ivoire and Madagascar in the past few weeks.

Cameroon and Cote d’Ivoire reported co-circulation of influenza A(H1N1)pdm09 and B. After peaking at the end of May, influenza activity in Madagascar is beginning to decrease, although the percent of specimens that tested positive for influenza is still high with 43%.

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Tropical Asia

Influenza transmission in South East Asia gradually decreased and transmission in southern Asia remained consistently low in the past few weeks. The proportion of influenza A has also been higher compared to influenza B in both regions. In South East Asia, influenza activity remained low for most countries except for Viet Nam, with predominantly circulation of A(H3N2) and A(H1N1)pdm09 viruses in the past few weeks.

Thailand also reported a small increase of A(H3N2) compared to the last few weeks.

In southern Asia, Sri Lanka reported increased influenza A activity compared to influenza B for the past few weeks.

In India A(H3N2) viruses remained predominant but at a decreasing rate compared to several weeks ago. Iran and Pakistan also experienced low activity. In Southern China the influenza A(H1N1)pdm09 activity gradually decreased.

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Countries in the temperate zone of the southern hemisphere

Temperate countries of South America

In temperate South America, acute respiratory illness activity was high and with increasing trends. Increased influenza-like-illness (ILI) and SARI activity was mainly due to respiratory syncytial virus (RSV), but the proportion of influenza positive viruses increased, with co-circulation of influenza A(H1N1)pdm09 and A(H3N2).

In Argentina, ILI and SARI activity were above the epidemic threshold and showed an increasing trend. So far in this season more than half of all samples positive for respiratory viruses were RSV, but the detection of Influenza virus has increased in the last weeks and the number of positive samples is higher than what has been seen in earlier seasons (excluding 2009). From the 736 samples that have been tested since May 2013, 99% (728) were influenza A and 1% (8) influenza type B. Form the 574 influenza A samples subtyped 89% (509) were influenza A(H1N1)09pdm 11% (65) influenza A(H3N2). While RSV is the main virus identified in children up to 10 years influenza is the main identified virus in those above 15 years of age.

Influenza activity in Chile is also increasing, also RSV remained to be the most prevalent virus detected. The national ILI consultation rate continued to show an increasing trend and was at the epidemic threshold level during the last weeks. Among the 3060 samples collected, 36% were positive for respiratory viruses and 12% were positive for influenza viruses. Among the positive samples, 48% were RSV and 29% were influenza A(H1N1)pmd09 or A not subtyped.

In Paraguay, ILI consultation rates, the ILI proportion, and the proportion of SARI-related hospitalizations remained similar to previous weeks with increasing trends. Of the 463 samples analyzed since 9 June, 57% tested positive for respiratory viruses and 16% tested positive for influenza viruses. Among the positive samples, RSV (69%) and influenza A(H3N2) (23%) were the most detected viruses. Among the 148 samples from SARI cases, RSV was the most detected virus.

In Uruguay, the proportions of SARI hospitalizations and SARI-related ICU admissions continued to increase, although SARI deaths have decreased over the past three weeks. Among 77 samples processed since 9 June, 34% tested positive for respiratory viruses and 18% for influenza viruses. The proportion of samples that tested positive for influenza are increasing and RSV is no longer the predominant virus. Of the 26 samples that tested positive, 12 (46%) were influenza A(H1N1)pmd09 and 9 (35%) were RSV.

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Temperate countries of South Africa

In South Africa, increasing trends of ILI and SARI cases have been reported. Influenza activity continued to increase since the season started in late April. Influenza A(H1N1)pmd09 remains the predominant circulating strain, although influenza A(H3) has also been reported.

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Oceania, Melanesia and Polynesia

Australia, New Zealand and the Pacific Islands continued to report low influenza activity.

During 16 to 22 June 2013 in Australia, of 278 ILI samples received, 4 were positive for influenza A(H3). In New Zealand, during 7 to 23 June 2013, influenza activity continued to remain below the baseline threshold with increasing trends. Twenty-two out of 226 samples received were positive for influenza: 11 were influenza B (lineage not determined), 6 was influenza A(H3N2), 3 were influenza A(H1N1)pdmo9 and 2 influenza A (not subtyped).

 

Source of data

The Global Influenza Programme monitors influenza activity worldwide and publishes an update every two weeks.

The updates are based on available epidemiological and virological data sources, including FluNet (reported by the Global Influenza Surveillance and Response System) and influenza reports from WHO Regional Offices and Member States. Completeness can vary among updates due to availability and quality of data available at the time when the update is developed.

 

Link to web pages

Contact fluupdate@who.int

 

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