INFLUENZA: WORLD HEALTH ORGANIZATION GLOBAL UPDATE
Influenza Update No. 196 - 14 Oct 2013
Although in many European countries influenza-like illness activity started to increase, influenza activity in the northern hemisphere temperate zones remained at inter-seasonal levels.
In most regions of tropical Asia, influenza activity was at a low level, with the exception of Hong Kong Special Administrative Region, China, where influenza transmission increased due to influenza A(H3N2).
In the Caribbean region of Central America and tropical South American countries, cases of influenza decreased, while acute respiratory illness remained stable in the Caribbean and Central America.
Respiratory syncytial virus (RSV) predominated, but the RSV activity remained within expected seasonal levels.
Influenza activity peaked in the temperate countries of South America and in South Africa in late June 2013. Temperate South American countries reported acute respiratory disease activity within expected seasonal levels, and RSV activity largely declined.
In Australia and New Zealand, numbers of influenza viruses detected and rates of influenza-like illness seemed to have peaked.
Co-circulation of influenza A(H1N1)pdm09, A(H3N2) and B viruses was reported in both countries.
Countries in the temperate zone of the northern hemisphere
Overall influenza activity in North America remained at low levels throughout the region. In Canada and the United States of America, influenza activity remained at interseasonal levels. In Mexico, influenza activity remained low after a period of 2 months (July-August 2013) with higher influenza activity.
Influenza activity in Europe remained at interseasonal levels. None of the specimens collected from sentinel sites between 10-22 Sep 2013 tested positive for influenza. However, many countries started reporting increased consultation rates for influenza-like illness
(ILI) and acute respiratory infection (ARI).
Northern Africa and the Western Asia region Influenza activity was low in the Northern Africa and western Asia regions. Only Qatar reported influenza activity, mainly influenza A virus (not subtyped), since the end of August 2013.
Influenza activity in the temperate region of Asia remained at interseasonal levels since late May 2013. In Mongolia, clinical activity started to increase since mid-August 2013, but no influenza viruses were detected in this period.
Countries in the tropical zone
Tropical countries of the Americas/Central America and the Caribbean:
Overall influenza activity in the Caribbean and Central America was at a low level throughout the region. Decreasing numbers of influenza A virus have been seen throughout the region, but influenza transmission had largely come to an end in the last few weeks in these countries.
Co-circulation of influenza A(H3N2) and influenza B viruses were reported, and RSV predominated among respiratory viruses in Costa Rica, El Salvador, Nicaragua, and Panama.
In tropical South America, respiratory virus activity continued decreasing following a period of high influenza activity in July and August 2013. In Colombia, the proportions of outpatient visits, hospitalizations, and ICU admissions were similar to reports for the same period in previous years. In Venezuela, ARI and pneumonia levels were reported within the expected values for the time of year. In Ecuador, the number of positive influenza samples steadily decreased since its influenza peak in August 2013. In Peru, reports of ARI in children under 5 years of age have been increasing since July 2013, but were consistent with levels from previous years. In the Plurinational State of Bolivia, the proportion of SARI-related hospitalizations were reported as elevated compared to the data from the same period last year , and laboratory data from CENETROP [National Center of Tropical and Infectious Diseases] in Santa Cruz showed that of 182 SARI samples analyzed in the beginning of October 2013, 33 percent were positive for a respiratory virus (a 9 percent increase from the previous week). Brazil showed a continuing decline in the number of positive influenza samples since July 2013, and among recent positive samples, influenza A un-typed and influenza B viruses were detected.
Central African tropical region
Cote d'Ivoire, Ghana, and Kenya reported circulating influenza viruses. In Cote d'Ivoire and Ghana, influenza B and A(H3N2) were the predominant viruses detected. Kenya reported low influenza activity due to both influenza A(H3N2) and influenza B viruses.
Influenza transmission in southern and Southeast Asia was low in most countries. Both influenza A(H1N1)pdm09 and A(H3N2) viruses were reported in this area. Since early July 2013, an increase in influenza transmission was seen in Hong Kong Special Administrative Region (SAR), China. The influenza transmission in Hong Kong SAR was predominated by influenza A(H3N2) virus. This increased transmission was also seen in the influenza associated hospital rates in this region; mainly the rates among 0-4-year-old patients increased over the past month. In the south of China, influenza activity remained at an interseasonal level. However, the number of influenza virus detections has been higher in this year's  interseasonal period compared to the previous year.
Countries in the temperate zone of the southern hemisphere
Temperate countries of South America
In the temperate countries of South America, ARI activity was reported at expected levels for the time of year, and RSV continued to be the most common respiratory virus detected in Argentina and Chile, although cases had largely decreased. In Argentina, ILI activity continued its decreasing trend since its peak in June and July of this year . In Chile, the proportion of SARI-associated hospitalizations continued to decrease. In Paraguay, the ILI consultation rate was higher than expected for the time of year but with decreased influenza and respiratory virus detection. In Uruguay, the proportion of SARI-associated hospitalizations increased from levels reported in the previous week, but proportions of ICU admissions continued to decline.
Temperate countries of Southern Africa
After a peak in influenza activity in South Africa due to influenza A(H1N1)pmd09 in June 2013, a small 2nd peak was observed in the last few weeks due to increased influenza A(H3N2) and influenza B circulation.
Overall, in Australia, New Zealand, and the Pacific Islands, influenza activity seemed to have peaked.
In Australia, during the period from 30 Aug to 13 Sep 2013, the distribution of influenza types and subtypes was variable across jurisdictions. In Western Australia, influenza A(H3N2) remained the predominant virus subtype; however, the proportion of A(H1N1)pdm09 increased. Influenza type B continued to represent over half of Victoria's influenza notifications. In recent weeks, there have been increasing proportions of influenza B virus in Queensland and South Australia. Influenza positivity levels ranged from 15 percent (309/2114) in the national sentinel laboratory surveillance to 28.1 percent (56/199) in the Australian Sentinel Practices Research Network (ASPREN). The Influenza Complications Alert Network (FluCAN) sentinel hospital surveillance system reported that the rate of influenza associated hospitalisations had been relatively stable since mid-August 2013. Almost 15 percent of influenza associated hospitalisations were admitted directly to the ICU. The age distribution of hospital admissions showed peaks in the 0-9 and over 60 years age groups.
In New Zealand, ILI activity was almost at the baseline threshold in early September 2013 but decreased since then. Out of 303 samples received in the last week, 161 were positive for influenza (53 percent): 49 were influenza B, 16 were influenza A(H3N2), 22 were influenza A(H1N1)pdm09, and 74 were influenza A (not subtyped). In Auckland and Counties Manukau District Health Boards, decreased influenza activity was reported in community surveillance and hospital surveillance.
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