[Source: World Health Organization, full page: (LINK). Edited.]
Influenza Update N° 188, 21 June 2013
- Influenza activity in the northern hemisphere temperate zones decreased to low levels.
- Similarly, influenza activity decreased in most regions of tropical Asia except for Sri Lanka and Viet Nam where activity of influenza A continued increasing.
- In Central America and the Caribbean, influenza activity remained low or similar compared to previous weeks, except in Cuba and the Dominican Republic where increasing influenza activity was reported.
- Influenza activity in the southern hemisphere started to increase slightly in South America and in South Africa but remained low in Oceania. In South America, respiratory syncytial virus remained the predominant circulating virus, but the proportion of influenza positive viruses was increasing.
For information on H7N9 in China please see link: http://who.int/influenza/human_animal_interface/influenza_h7n9/en/index.html
Countries in the temperate zone of the northern hemisphere
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 3.4% testing positive in the last week of May. Influenza B remained the most prevalent circulating influenza virus. The national influenza-like-illness (ILI) consultation rate has remained stable during the last eight weeks, but was still above the expected range for the past five weeks.
In the United States of America (USA), influenza activity continued to decline and has returned to inter-seasonal levels. Nationally, the proportion of ILI outpatient consultations decreased to 0.9%, below the national baseline of 2.2%. Of 2746 specimens tested and reported by collaborating laboratories, 177 (6.5%) were positive for influenza. Influenza B remained the most prevalent circulating influenza virus.
Mexico has reported relatively stable influenza activity over the last few weeks with the majority being influenza A(H3N2). From mid-May to the first week of June, 7.5% of specimens tested positive for influenza. Among the positive specimens, 71.5% of those were influenza A(H3N2).
Influenza activity continued to decline in Europe and is now at inter-seasonal levels of transmission for the region. Consultation rates for ILI and acute respiratory infection (ARI) were at low levels for all countries in the region. Of the specimens collected from sentinel sites, 2 out of 98 (2%) tested positive for influenza. Of the 116 influenza virus detections reported since 20 May, 66% were characterized as influenza B.
Northern Africa and the Western Asia region
Influenza activity seems to be at inter-seasonal levels in Northern Africa and Western Asia region. Most countries in the western Asia region have mainly detected influenza A(H1N1)pdm09 throughout the season, with the exception of Jordan and Pakistan which reported a majority of influenza B, especially in the last several weeks.
Influenza activity in much of the temperate region of Asia has decreased gradually over the past several weeks and has is coming to inter-seasonal levels.
In China, as of May 30, 2013, 132 cases of influenza A(H7N9) have been identified, of which 39 have died, more and updated information will be posted at: http://who.int/influenza/human_animal_interface/influenza_h7n9/en/index.html
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 was reported. Acute respiratory illness in countries remained low or within expected levels, with the proportion of severe acute respiratory infection (SARI) hospitalizations at 2.6%.
Cuba reported increasing influenza activity, with 35.7% of 462 specimens testing positive for influenza viruses since mid-May. Of those that were positive for influenza A, 96% were influenza A(H1N1)pmd09 and the remaining were influenza A(H3N2). Rhinovirus and para-influenza are also circulating in Cuba.
Influenza activity also increased in the Dominican Republic out of 218 samples tested, the proportion testing positive for influenza increased from 14.6% four weeks ago to 75% in the most current week, with influenza A(H1N1)pmd09 being the most detected virus. Since January 2013, nine deaths due to influenza A(H1N1)pdm09 virus were reported, including four pregnant women.
In tropical South America, ARI activity remained at same levels except in Colombia and Venezuela, where influenza A(H1N1)pmd09 continued to circulate.
In Colombia, the proportion of SARI hospitalizations and SARI ICU admissions continued to increase. Of the 436 specimens analyzed in the past two weeks, 27% tested positive for all respiratory viruses. Forty-eight percent of those that tested positive for all respiratory viruses were influenza A(H1N1)pmd09.
Venezuela has 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 but remains at expected levels. Of the samples that were positive for influenza, 84.2% were due to influenza A(H1N1)pdm09 followed by influenza A(H3N2).
Central African tropical region
Many countries in the Central African tropical region reported low activity, with the exception of Cameroon, Cote d’Ivoire, Kenya and Madagascar in the past few weeks. Cameroon, Cote d’Ivoire reported co-circulation of influenza A(H1N1)pdm09 and B, while Kenya detected influenza B and A(H3N2).
Influenza transmission in South East Asia gradually decreased and transmission in southern Asia remained consistently low in the past few weeks. However, of the number of viruses tested, the proportion of influenza A increased relative to influenza B in both regions.
In South East Asia, influenza activity remained low for most countries except for Vietnam, which reported an increasing number of A(H1N1)pdm09 viruses.
In southern Asia, Sri Lanka reported increased influenza A activity compared to influenza B for the past few weeks. In India A(H3N2) viruses were predominant with much lower A(H1N1)pdm09 circulation compared to several weeks ago. Iran and Pakistan also experienced low activity. In Southern China the influenza activity also remained low.
Countries in the temperate zone of the southern hemisphere
Temperate countries of South America
In temperate South America, acute respiratory illness activity continued to increase and was reported as close to or at the epidemic threshold in the southern cone. 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 influenzaA(H1N1)pdm09 and A(H3N2).
Influenza activity in Argentina continued to follow the curve of what is expected for this time of year. Of the 2445 samples analyzed in Argentina since 1 June, 43% were positive for a respiratory virus. Of those that tested positive, 57% were due to RSV and 18% to influenza A(H1N1)pmd09.
Influenza activity in Chile also increased, although RSV continued to be the most prevalent virus detected. The national ILI consultation rate continued to show an increasing trend and is now at the epidemic threshold level. Among the 2405 samples collected, 31% were positive for respiratory viruses. Among the positive samples, 40% were RSV, 18% parainfluenza, 17% influenza A(H1N1)pdm09 and 12% influenza A not subtyped.
Paraguay reported increased ILI consultation rates. Of the 289 samples analyzed since 1 June, 35% tested positive for respiratory viruses. Among the positive samples, RSV (76%) and influenza A(H3N2) (15%) were the most detected viruses followed by influenza A(H1N1)pdm09. Among the 109 samples from SARI cases, RSV was the most detected virus.
In Uruguay, the proportions of SARI hospitalizations and SARI-related ICU admissions increased over the last weeks. Among 46 samples processed since 1 June, 26% tested positive for respiratory viruses and 4% for influenza viruses. RSV was the most detected virus.
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 was the predominant circulating virus, constituting 35.6% of the 464 samples collected n from sentinel sites in nine provinces.
Oceania, Melanesia and Polynesia
Australia, New Zealand and the Pacific Islands continued to report low influenza activity.
During 2 to 8 June 2013 in Australia, of 234 ILI samples received, 3 were positive for influenza A(H1N1) pdm09, 3 for influenza A(H3) and 1 influenza B(lineage not determined).
In New Zealand, during 3 to 9 June 2013, influenza activity continued to remain below the baseline threshold. 15 out of 202 samples received were positive for influenza: 12 were influenza B (lineage not determined), 1 was 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
- Epidemiological Influenza updates: http://www.who.int/influenza/surveillance_monitoring/updates/latest_update_GIP_surveillance
- Epidemiological Influenza updates archives 2012: http://www.who.int/influenza/surveillance_monitoring/updates/GIP_surveillance_2012_archives
- Virological surveillance updates : http://www.who.int/influenza/gisrs_laboratory/updates/summaryreport
- Virological surveillance updates archives : http://www.who.int/influenza/gisrs_laboratory/updates/en/index.html