Influenza update - 352

14 October 2019 - Update number 352, based on data up to 29 September 2019

Information in this report is categorized by influenza transmission zones, which are geographical groups of countries, areas or territories with similar influenza transmission patterns. For more information on influenza transmission zones, see the link below:


  • In the temperate zones of the southern hemisphere, influenza activity was low in most countries, and appeared to decrease in Chile after a second wave of influenza activity of predominately B viruses.
  • In the Caribbean, and tropical South American countries, influenza activity was low overall. In Central American countries, influenza activity increased in El Salvador and Nicaragua.
  • In tropical Africa, influenza activity was low across reporting countries except for some countries in Western Africa.
  • In Southern Asia, influenza activity was low across reporting countries except in Bhutan where influenza activity continued to be reported above alert threshold.
  • In South East Asia, influenza activity was low in most reporting countries but appeared to increase in Lao PDR.
  • In the temperate zone of the northern hemisphere, influenza activity remained at inter-seasonal levels in most countries. Influenza season appeared to have started across the countries of the Arabian Peninsula.
  • Worldwide, seasonal influenza A viruses continued to account for the majority of detections, though the proportion of influenza B viruses increased in recent weeks.

National Influenza Centres (NICs) and other national influenza laboratories from 94 countries, areas or territories reported data to FluNet for the time period from 16 September 2019 to 29 September 2019 (data as of 2019-10-11 01:51:30 UTC). The WHO GISRS laboratories tested more than 63162 specimens during that time period. 3494 were positive for influenza viruses, of which 1946 (55.7%) were typed as influenza A and 1548 (44.3%) as influenza B. Of the sub-typed influenza A viruses, 447 (35.5%) were influenza A(H1N1)pdm09 and 813 (64.5%) were influenza A(H3N2). Of the characterized B viruses, 56 (14.3%) belonged to the B-Yamagata lineage and 336 (85.7%) to the B-Victoria lineage.

The WHO Consultation and Information Meeting on the Composition of Influenza Virus Vaccines for Use in the 2020 Southern Hemisphere Influenza Season was held on 23-26 September 2019 in Geneva, Switzerland. It was recommended that trivalent vaccines contain the following: an A/Brisbane/02/2018 (H1N1)pdm09-like virus; an A/South Australia/34/2019 (H3N2)-like virus; and a B/Washington/02/2019-like (B/Victoria lineage) virus. It was also recommended that quadrivalent vaccines containing two influenza B viruses contain the above three viruses and a B/Phuket/3073/2013-like (B/Yamagata lineage) virus.

The vaccine recommendation for the 2020 Southern Hemisphere Influenza Season can be consulted at this link below:

Detailed influenza update

Influenza fact sheet

Seasonal update

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 WHO Global Influenza Surveillance and Response System), FluID (epidemiological data reported by national focal points) 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.