# 5035
In 1968 a new influenza strain – H3N2 – was identified in Hong Kong and quickly spread around the world as the third (and mildest) influenza pandemic of the 20th century.
H3N2 supplanted the H2N2 virus that had been around since the previous pandemic in 1957. It was dubbed the Hong Kong Flu, and until 1977, was to be the only influenza A strain in circulation.
H1N1 returned in 1977 under mysterious circumstances, as the Russian Flu (many believe it escaped from a Russian lab).
From 1977 till 2009 these two viruses co-circulated around the world, each drifting, mutating, and evolving gradually over time.
Some years H1N1 would be the main strain seen, while other years it would be the descendents of the Hong Kong Flu. Years where H3N2 made up the bulk of influenza A infections tended to produce worse flu seasons and a greater number of fatalities, especially among the elderly.
At roughly the same time that the 2009 H1N1 virus appeared – a new, mutated strain of H3N2 appeared as well. It was overshadowed, and outpaced by the novel H1N1 virus, and for awhile it looked as if it might not survive alongside swine flu.
But H3N2 hung on, and has been showing up in increasing numbers around the world over the past few months.
This mutated `Perth’ strain of the H3n2 virus has changed sufficiently to make older vaccinations, and previous exposures, less likely to provide immunity.
The good news is that it is covered in this year’s flu vaccine.
While flu activity remains low around the world, we are starting to see reports of outbreaks – including this one from Japan - where a half dozen patients died in one hospital from the H3N2 virus in less than a week.
Their ages ranged from 60 to 90, and they are among several dozen who have been sickened. Hospital staff and patients are both reportedly experiencing flu symptoms.
Although the AP and others picked up on this story yesterday, FluTrackers created a thread with translations of the original Japanese press reports early Saturday morning (Hat Tip Makoto), and has updated the story since then.
You can read them here. The latest update gives this timeline.
25 patients and 8 staffs are suffering from influenza now
29 Oct., vaccinated against the flu
31 Oct., a man died(eighties)
2 Nov., 2 men died(sixties, nineties) a woman died(seventies)
4 Nov., a woman died(eighties)
5 Nov., a man died(eighties)
The short time span between vaccination and outbreak could simply mean that the vaccine did not have time (typically 2-3 wks) to convey any protective antibodies to the recipients (many of whom were elderly, and less likely to mount a robust immune response, anyway).
An alternative theory is being bandied about the Internet that somehow the vaccine contributed to this outbreak or the fatality rate.
Since correlation doesn’t necessarily imply causation, until we see evidence considerably more substantial than just a short gap between the vaccinations and the outbreak, these sorts of theories while interesting, remain highly speculative.
On the face of it, this would seem to be an unusually severe outbreak - suggestive of perhaps a change or drift in the virus.
Again, a possibility.
But there is a lot we don’t know about this story yet, including information on any pre-existing conditions these fatal cases may have had.
There may simply be less to this story than it at first appears. It will likely take a few days to get answers.
Obviously we will await any word of sequence analysis of this strain, and an investigation into any potential link to the administration of the flu vaccine, with considerable interest.
In the meantime, with flu season on its way and likely to feature this drifted H3N2 virus, getting vaccinated now – while you still have time to build immunity – still (until proven otherwise) remains your best option to avoid the flu this year.
