WHO

Summary

Influenza activity remained high in the temperate zone of the northern hemisphere while in the temperate zone of the southern hemisphere activity was at inter-seasonal levels. Worldwide, influenza A accounted still for the majority of influenza detections but influenza B (mostly B-Yamagata lineage) increased in recent weeks.

Up to now, the majority of countries which are in the influenza season, reported influenza- like illness reaching moderate levels in comparison with previous years, with few reaching levels exceeding those of previous years. Some countries however have reported levels of hospitalization and ICU admissions reaching or exceeding peak levels of previous influenza seasons. WHO recommends countries with current influenza activity or entering their season to adopt necessary measures for ensuring appropriate case management, compliance with infection control measures and seasonal influenza vaccination for high risk groups(see also the fact sheet given below).

• Influenza (Seasonal) fact sheet

• Overall, influenza virus activity remained high in the region. In Canada, influenza activity remain elevated while influenza-like illness (ILI) activity continued to increase and was above the 5-year average for this time of the year. Influenza B detections increased in recent weeks reaching equal proportion as influenza A detections. In the United States of America (USA), influenza activity remained high, with influenza A (H3N2) viruses most frequently detected followed by influenza B viruses. Hospitalization cumulative rate for influenza were reported at high levels, and above levels observed during the same period over the previous seven seasons. In both Canada and the USA, adults aged 65 years and older accounted for the majority of influenza cases and influenza-related hospitalizations. In Mexico, influenza activity decreased slightly, with influenza A(H3N2) virus predominantly detected.
• In Europe, influenza activity remained high in most countries. All seasonal influenza subtypes co-circulated across the region, but influenza B virus predominated in most countries. ILI and influenza detections increased further in most countries in Eastern and Northern Europe, and appeared to have peaked in few countries in Southwestern Europe. Influenza B detections increased in Denmark, Estonia, Norway, and Sweden. Influenza illness indicators appeared to decrease in Ireland and the United Kingdom, but influenza-related hospitalizations remain high in England.
• In Northern Africa, influenza detections remained high in Algeria, Egypt and Morocco, and continued to decrease in Tunisia. Influenza A(H1N1)pdm09 virus predominated in Algeria and Tunisia, and detections of influenza A(H1N1)pdm09 and influenza B were reported in Egypt and Morocco.
• In Western Asia, influenza activity continued to be reported across the region. In some countries of the Arabian Peninsula, influenza activity appeared to have peaked, while increased influenza A(H1N1)pdm09 detections were reported in Iraq. In Israel, influenza activity remained high with influenza B viruses predominating. Detections of influenza B-Yamagata lineage and influenza A(H1N1)pdm09 were reported in Armenia.
• In Central Asia, influenza A and B detections increased across the region in recent weeks.
• In East Asia, influenza activity remained high across the region. ILI activity appeared to decrease in Northern and Southern China but influenza detections remained elevated, with influenza B-Yamagata lineage and influenza A(H1N1)pdm09 viruses predominating. ILI consultation rate remained high in Hong Kong SAR, China, with influenza B most frequently detected. Decreased detections of influenza A(H1N1)pdm09 were reported in the Democratic People’s Republic of Korea. In Mongolia, respiratory illness indicators and influenza detections appeared to decrease whit influenza B-Yamagata lineage virus predominately detected in recent weeks. In the Republic of Korea, ILI activity decreased although influenza A(H3N2) and B virus detections remained high.
• In Southern Asia, influenza activity remained low in general. Detection of influenza A(H1N1)pdm09 and influenza A(H3N2) viruses continued to increase in Pakistan, while activity decreased in the Islamic Republic of Iran.
• In South East Asia, low levels of influenza activity were reported in most countries. Increased detections of influenza A(H1N1)pdm09 and influenza B-Yamagata lineage viruses were reported in Singapore.
• In Western Africa, little to no influenza activity was reported across the region. In Middle Africa, there were no updates available for this reporting period. In Eastern Africa, increased influenza A(H1N1)pdm09 detections were reported in Madagascar.
• In the Caribbean and Central American countries, respiratory illness indicators and influenza activity remained low in general. Influenza activity increased in Puerto Rico, with influenza A(H3N2) and B viruses co-circulating. Increased detections of influenza B virus were reported in Suriname. Influenza activity decreased in Jamaica.
• In the tropical countries of South America, influenza activities and respiratory illness indicators were generally low with a few exceptions. Influenza A(H3N2) detections slightly increased in Colombia. Influenza activity remained elevated in Ecuador, with influenza A(H1N1)pdm09 virus predominating.
• In the temperate zone of the Southern Hemisphere, influenza activity remained overall at inter-seasonal levels.
• National Influenza Centres (NICs) and other national influenza laboratories from 104 countries, areas or territories reported data to FluNet for the time period from 22 January 2018 to 04 February 2018 (data as of 2018-02-16 04:33:50 UTC).The WHO GISRS laboratories tested more than 302596 specimens during that time period. 98068 were positive for influenza viruses, of which 54142 (55.2%) were typed as influenza A and 43926 (44.8%) as influenza B. Of the sub-typed influenza A viruses, 10290 (58%) were influenza A(H1N1)pdm09 and 7441 (42%) were influenza A(H3N2). Of the characterized B viruses, 7553 (92.5%) belonged to the B-Yamagata lineage and 615 (7.5%) to the B-Victoria lineage.