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It's been less than a week since the first reports out of Pakistan that cases of bird flu were appearing there. At the time we warned that the coming of flu season meant these kinds of reports were to be expected, but by the weekend concern increased as a family cluster appeared. As common in the…
WHO [World Health Organization] is now saying that human to human (H2H) transmission has not been ruled out in China or Pakistan:
China:
The World Health Organization said Friday it was impossible to say whether a case of bird flu in China involving a 52- year-old man was due to human-to-human…
Swine flu infection of health care workers (or as CDC refers to them, health care personnel or HCP) was of interest early in the pre-pandemic phase for at last two reasons. One was the obvious goal of estimating the risk to front line workers and devising best practices for their protection.…
by revere, cross-posted from Effect Measure
Swine flu infection of health care workers (or as CDC refers to them, health care personnel or HCP) was of interest early in the pre-pandemic phase for at last two reasons. One was the obvious goal of estimating the risk to front line workers and…
There are still a few puzzling things about these clusters. Firstly, why are only family members affected? There are two other plausible interpretations of the data. The WHO has not published much on the recent findings that the virus can be passed on by eating infected birds. One of the most common ways is the ingesting of raw duck's blood which is common in that part of the world. It has now been shown that the H5N1 virus is not only a respiratory virus but can infect the GI tract, both in birds and humans. About 30% of human cases show major symptoms of GI infection with the virus. Thus there is much more possibility of active virus in the food portions of birds than was previously thought.
GI infection has the possibility of transfer through contaminated water too.
Another possibility for the clusters only including close family members is that there is a unique gene in a minority of the population which makes the carrier much more susceptible to infection. This gene would be present in close family members.
The WHO and CDC are both claiming that the genetic sequence of the virus isolated from the family cluster does not show any mutations or mixing with swine flu genes. However, they have not put the sequence on a publicly available site.
Certainly we have to keep up to date on what is happening but I don't think that things have changed too much with the latest outbreaks. There is every possibility that sickness and deaths have been misdiagnosed in the past so we are not really seeing an upswing in the number of those clusters.
Ian Forrester
Both Declan Butler in Nature and we at Effect Measure have received additional information about the genetic sequences. The cleavage site is avian HPAI. There is E627K in PB2, that is, this is a mammalian adapted virus. This mutation has been seen before in Indon and Turkey. The viral load seems higher than other samples. WHO did not release this information for reasons that are not clear. There is also a distinct lineage from other human cases suggesting more than one interspecies event.