Influenza Update N° 390

Summary 

• The current influenza surveillance data should be interpreted with caution as the ongoing COVID-19 pandemic has influenced to varying extents health seeking behaviours, staffing/routines in sentinel sites, as well as testing priorities and capacities in Member States. The various hygiene and physical distancing measures implemented by Member States to reduce SARS-CoV-2 virus transmission have likely played a role in reducing influenza virus transmission.  
• Globally, despite continued or even increased testing for influenza in some countries, influenza activity remained at lower levels than expected for this time of the year. 
• In the temperate zone of the northern hemisphere, influenza activity remained below baseline, though sporadic detections of influenza A and B viruses continued to be reported in some countries.  In the temperate zone of the southern hemisphere, influenza activity was reported at inter-seasonal level.
• In the Caribbean and Central American countries, no influenza detections were reported. 
• In tropical South America, no influenza but low levels of detection of other respiratory viruses (ORVs) were reported in some countries. 
• In tropical Africa, influenza activity was reported in some reporting countries in Western and Eastern Africa in recent weeks.
• In Southern Asia, sporadic influenza detections were reported in India and Nepal.
• In South East Asia, influenza A(H3N2) detections continued to be reported in Lao People's Democratic Republic (PDR). 
• Worldwide, influenza B detections accounted for the majority of the very low numbers of detections reported.
• National Influenza Centres (NICs) and other national influenza laboratories from 85 countries, areas or territories reported data to FluNet for the time period from 01 March 2021 to 14 March 2021 (data as of 2021-03-26 08:06:28 UTC).The WHO GISRS laboratories tested more than 291427 specimens during that time period. A total of 375 specimens were positive for influenza viruses, of which 132 (35.2%) were typed as influenza A and 243 (64.8%) as influenza B. Of the sub-typed influenza A viruses, 5 (6.1%) were influenza A(H1N1)pdm09 and 77 (93.9%) were influenza A(H3N2). Of the characterized B viruses, 0 (0%) belonged to the B-Yamagata lineage and 188 (100%) to the B-Victoria lineage.
• During the COVID-19 pandemic, WHO encourages countries, especially those that have received the multiplex influenza and SARS-CoV-2 reagent kits from GISRS, to continue routine influenza surveillance, test samples from influenza surveillance sites for influenza and SARS-CoV-2 viruses where resources are available and report epidemiological and laboratory information in a timely manner to established regional and global platforms. Updated considerations for addressing disruptions in the influenza sentinel surveillance and extending to include COVID-19 wherever possible are available in the interim guidance, Maintaining surveillance of influenza and monitoring SARS-CoV-2 – adapting Global Influenza surveillance and Response System (GISRS) and sentinel systems during the COVID-19 pandemic. Updated algorithms for testing of both influenza and SARS-CoV-2 for surveillance are also included.