# 4844
At about the same time that the pandemic H1N1 virus began its rapid spread around the world, reports of an antigenically drifted version of seasonal H3N2 appeared as well (see Who Knew? New Flu).
This new strain, dubbed A/Perth/16/2009-like H3N2 virus, failed to compete successfully with the emerging pandemic strain, and really hasn’t circulated widely over the past 12 months.
It has, however, continued to show up in scattered surveillance reports from parts of Africa, Asia, and South America.
Analysis of this new H3 virus suggests that exposure to earlier H3N2 viruses – or even taking last year’s seasonal flu vaccine - is unlikely to convey much (if any) immunity to this new strain.
And H3N2, unlike the recent H1N1 virus, is no respecter of age, and so it is likely to affect those over 65 as well as younger patients.
The good news is that this year’s seasonal flu vaccine contains antigens against this new strain.
Whether this H3N2 virus ends up having a big impact on this year’s flu season is impossible to know right now.
But the fact that immunity to this strain in the community is probably very low, and the virus continues to circulate, suggests that it might.
The CDC released a HAN (Health Alert Network) Message earlier this month on the recent detection of H3N2 in the United States called Seasonal Influenza A (H3N2) Virus Infections.
Which brings us to a report out of Hanoi, Vietnam (courtesy of the incredibly hard working Arkanoid Legent) on the level of H3N2 influenza cases they are currently seeing.
This from the Saigon Daily.
Doctors concerned about likely expansion of H3N2 flu virus in Hanoi
Saturday ,Aug 28,2010, Posted at: 17:41(GMT+7)
Medical workers fretted that seasonal H3N2 flu virus continued to be widespread in Hanoi and the disease is likely to erupt into epidemic.
Seasonal influenza viruses, H1N1 and H3N2, flow out of overlapping epidemics in Vietnam. Meanwhile H1N1 has been controlled, most influenza infections this season have been attributed to influenza A (H3N2) viruses.
According to Dr. Nguyen Hong Ha, deputy director of the National Institute of Infectious and Tropical Diseases, there has been an increase of H3N2 patients. The hospital receives over 130 people suffering from the flu a day, doubling the number of last weeks.
While reports of H3N2 over the past year have been sporadic, and widely scattered. A few blogs on these reports from the past couple of months include:
Singapore: H1N1 No Longer Dominant Strain
Global Flu Activity Update
Transitions: 3 Global Snapshots Of Flu Activity
Flu: Down, But Not Completely Out
