(Tue, 03 Jan 2012 15:52:00 +0000)
Today he has a post on the supposed CFR (Case Fatality Ratio) of the H5N1 virus.
The mantra in the popular press is that bird flu kills `60% of those infected’. We seen it used a lot over the past month, particularly in cautionary media stories regarding the dangers of bird flu research.
It’s a simplistic view, of course, because we don’t know how many mild or even asymptomatic cases occur that are never reported.
This is something we’ve discussed often, including last December, in Study: Subclinical H5 & H9 Infections In Humans, where we saw a report out of China on the detection of antibodies to both H9 and H5 avian influenza viruses among a small number of villagers in and around Beijing, China.
Similarly, last September we saw a study that reported the results of serological testing conducted in a rural village in Thailand in 2008 (see Bangladesh To Share H9N2 Bird Flu Virus).
Out of 800 villagers tested, the authors found 4.7% were seropositive for the Hong Kong H9N2 avian strain, 5.6% had antibodies to A/Thailand/676/2005 H5N1 bird flu, and 3.5% were shown to be seropositive to A/Thailand/384/2006 H5N1.
The implications of these studies are that human infection with these avian viruses – while still pretty rare – probably occur more often than current surveillance and reporting suggests.
And if true, that would dilute the 60% CFR number.
As Professor Racaniello explains, until we can get a good handle on how many `mild or asymptomatic’ infections occur, we really can’t determine the true fatality rate of the virus.
Follow the link below to read:
3 January 2012
By Vincent Racaniello
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