Influenza season is quite variable across the Northern Hemisphere, with some regions seeing much earlier onsets than others - and quite often - a different mix of viruses as well.
Last year, while North America struggled with an unusually severe H3N2 season, Asia was hit by a strong wave of Influenza B, and Europe by a combination of both Influenza B & A, with A/H1N1 outnumbering A/H3N2 by 2 to 1.While South Korea and Canada saw unusually early starts to their their winter flu seasons, Hong Kong just passed their epidemic threshold last week, and as of their latest report (epi week 51), Russia has yet to reach that mark.
Most other temperate regions of the Northern Hemisphere (U.S., many European countries, China, etc.) entered their winter flu season in December, with A/H1N1 the predominant subtype reported.
WHO EMRO has published the following summary of influenza activity reported during the month of December in the Eastern Mediterranean region, which - despite some gaps in the data - shows a continued increase in (primarily) Influenza A/H1N1 activity.
Influenza monthly update, December 2018
In the WHO Eastern Mediterranean Region, influenza activity continues to increase in the month of December in many countries reporting data to FluNet and EMFLU namely, Afghanistan, Bahrain, Egypt, Iran (Islamic Republic of), Iraq, Jordan, Kuwait, Lebanon, Morocco, occupied Palestinian territory (oPt), Oman, Qatar, Saudi Arabia, Sudan, Syrian Arab Republic and Tunisia.
Fig. 1. Influenza geographic spread in Eastern Mediterranean Region, December 2018
Influenza activity by subtype
• In December 2018, no new cases of human influenza A(H5N1) were reported in Egypt.
• In the northern Africa influenza transmission zone, A(H3) virus was detected predominantly in Egypt, while Morocco reported increase of activity with Influenza types A and B viruses co circulated.
• In the western Asia influenza transmission zone, Bahrain, Oman, Qatar and Saudi Arabia reported co-circulation of all seasonal influenza viruses, while in Kuwait only influenza B virus was detected. Jordan, Lebanon and oPt reported co circulation of A(H1N1)pdm09 and A(H3N2) while Iraq reported circulation of sporadic cases of the influenza A(H1N1)pdm09.
• In southern Asia transmission zone, Iran (Islamic Republic of) continued reporting circulation of all seasonal influenza viruses with A(H3N2) predominated , while Afghanistan reported sporadic co circulation of influenza types A and B viruses
Circulating influenza viruses by subtype
• During December 2018, national influenza centres and influenza laboratories in the Region tested a total of 12245 specimens for influenza viruses of which 2744 tested positive (22%).
• The average percentage of positivity rates is 22%, with highest positivity rate recorded in Bahrain, Oman Qatar and oPt.
• Of the viruses tested; 2039 (74%) were influenza A viruses, including 315 (11%) influenza A(H1N1)pdm09 virus and 919 (34%) were influenza A(H3) virus. Influenza B (Lineage Not determined) virus accounted for 705 (26%) (Figure 3).
Fig. 3. Circulating influenza viruses in the Region by subtype, Epi week 44-52, 2018