Weekly Virological Update on 21 July 2010
Virological Surveillance, week n° 27-2010 (4 July to 10 July 2010)
Trend of proportions of different type and subtype influenza viruses
Summary on week 27
- Overall influenza activity has remained at low levels in most parts of the world.
- In the Southern Hemisphere, co-circulation of pandemic A(H1N1) and seasonal A(H3N2) viruses has been reported.
- Influenza type B virus detections have decreased.
Global Virological Surveillance
Overall influenza activity has remained low. Globally 69,1% of the subtyped influenza A viruses were pandemic influenza A(H1N1). Influenza A activity was reported in some countries, including Australia, Chile, China, Ghana, Singapore and South Africa with co-circulation of pandemic A(H1N1) and A(H3N2) viruses. Sporadic influenza B activity has been observed in some countries with decreased detections in China (46.8% of all influenza detections).
FluNet Report (For the week 4 July to 10 July 2010)
The total number of specimens reportedly positive for influenza viruses by National Influenza Centres (NICs) from 15 countries was 320. Of these, 220 (69%) were typed as influenza A and 100 (31%) as influenza B.
From the start of the pandemic in 19 April 2009 to 10 July 2010, the total number of specimens reported positive for influenza by NIC laboratories was 649,983*. Of these, 490,946 (75.5%) were pandemic A(H1N1), 8,956 (1.4%) were seasonal A(H1N1), 34,711 (5.3%) were A(H3N2), 81,000 (12.5%) were A (not subtyped) and 34,243(5.3%) were influenza B.
Pandemic virus characterization
19 April 2009 to 18th July 2010 - cumulatively 155 countries shared a total of 26, 478 specimens (20,128 clinical and 6,350 isolates) with WHO CCs.
The majority of pandemic A(H1N1) 2009 influenza viruses analyzed to date are antigenically and genetically closely related to the recommended vaccine virus A/California/7/2009.
So far, 302 cases associated with oseltamivir resistant pandemic A(H1N1) viruses have been reported by GISN and other partners. All of these viruses showed the H275Y substitution and all remain sensitive to zanamivir. Click here to obtain more information on oseltamivir resistant viruses.
WHO, through the GISN, continues monitoring the evolution and global circulation of influenza viruses, including pandemic, seasonal and other influenza viruses infecting, or with the potential to infect humans.
* Some NICs report data to FluNet retrospectively and updates of previous data with new results are frequent.