Effect Measure

Wild birds and wild guesses

The fact seven people in Azerbaijan contracted bird flu from wild birds has been assumed for some time and now has been officially confirmed by researchers in Germany:

Four people have died after catching avian flu from infected swans, in the first confirmed cases of the disease being passed from wild birds, scientists have revealed.

The victims, from a village in Azerbaijan, are believed to have caught the lethal H5N1 virus earlier this year when they plucked the feathers from dead birds to sell for pillows. Three other people were infected by the swans but survived.

Andreas Gilsdorf, an epidemiologist at the Robert Koch Institute in Berlin, who led the team that made the discovery, said: “As far as we know this is the first transmission from a wild bird, but it was a very intensive contact. We know that the virus is carried by swans and we know that you can catch the virus if you have close contact, so it doesn’t change anything, it’s just the first time it has been reported.” (The Guardian)

The Azeri cases, date from last March, part of a group of seven teenaged victims, all but one of which were from the same family. In February swans migrating from Siberia appeared earlier and in larger numbersthan usual in Azerbaijan . Die-offs of swans in eastern Europe allso occurred in Azerbaijan. Simultaneously, human cases appeared in a village dependent on the hunting of wild birds for income. Plucking feathers from the dead birds was suspected as the exposure source early on. The viral isolates were related to the “Qinghai Lake” strain (Brown, FAO, abstract .pdf ).

Now it is no longer possible to say that you can’t get bird flu from wild birds. The contact with these birds was not casual, probably as close as many cases already documented from terrestrial poultry (chickens primarily). While on its face this doesn’t seem like a qualitatively different degree of exposure, it underlines once again that categorical statements meant to reassure are almost never a good idea. In recent weeks we have seen the “all cases have had close contact with infected or dead birds,” “no person to person transmission” and the “no wild bird source” mantras fall by the wayside. Correcting these statements that had no firm basis in evidence to begin with, damages credibility and requires still more qualification and tortured reassurances.

Here’s what we think the current state of knowledge is. There is an enormous amount of exposure to the H5N1 virus occurring daily. So far only a tiny fraction of these exposures have resulted in serious disease in humans. We don’t know why that is, nor do we know all the possible ways people might be exposed to the virus or why some people become clinically ill while others do not, given the same exposure. We don’t know if food, water, infected animals so far unidentified, inanimate objects or suspended aerosols are additional sources of exposure and hence rare infection. We don’t know if certain kinds of exposure are worse than others. We are not completely confident that many mild or inapparent infections are not occurring. Although so far we have not seen much evidence of this, there has been insufficient investigation.

The bottom line is we mostly don’t know how or why some people get serious infection with this very nasty virus. It seems true that at the moment it isn’t easy to become infected — for most people, anyway. Everything else is guessing or hoping.

Comments

  1. #1 David K NZ
    June 27, 2006

    A reference to multiple H5N1 infection sites from
    PLoS Medicine Volume 3 Issue 6 June 2006

    http://dx.doi.org/10.1371/journal.pmed.0030135

  2. #3 revere
    June 27, 2006

    Thanks. I know the authors. This is Cristina’s doctoral work, I believe. They make a very pertinent point.

  3. #4 Thinlina
    June 27, 2006

    Sorry to distract the thread, but would any of you have information about how these cases of pneumonic plague have been confirmed? PCR? Antigens?
    http://www.promedmail.org/pls/promed/f?p=2400:1001:8381126996294001018::NO::F2400_P1001_BACK_PAGE,F2400_P1001_PUB_MAIL_ID:1000,33379

  4. #5 revere
    June 27, 2006

    Thin: Probably smear or culture.

  5. #6 Thinlina
    June 28, 2006

    ok. thanks ;)

  6. #7 Man of Misery
    June 28, 2006

    A couple of things…
    1. “seven teenaged victims, all but one of which were from the same family” Any thoughts how/if this relates to the thought that the H2H2H cases in Indonesia were the re sult of some sort of familial genetics?

    2. Anybody know what the current status of the surveys of wild waterfowl in Canada/Alaska? Have we seen any evidence of transferrence to North America from Asia/Europe via the east-west migration?

  7. #8 revere
    June 28, 2006

    MoM: I have a hard time seeing genetic susceptibility as the sole explanation. A lot of the “blood relatives” are cousins, uncles, sibs, etc., who often don’t share that much genetically with each other. It would have to be an amazingly strong risk factor for this to be working. The only speculation I’ve seen has to do with receptor distributions but everyone is just guessing.

    Regarding wild birds, as far as I know there have been no high path H5N1 detections at this point. Anyone else have info?

  8. #9 anon
    June 29, 2006

    I’m wondering, whether H5N1 can spread by parasites
    in the feathers. Freyana anserina is quite common.

  9. #10 revere
    June 29, 2006

    anon: You mean the virus is infecting the parasite (on evidence parasites are competent hosts for influenza) or the virus is somehow physically on the parasite and gets to us tha way? But the parasite would then have to get to somewhere on us where there are cells with the proper receptors on it. Seems unlikely as a vector.

  10. #11 anon
    June 29, 2006

    maybe the virus infects the parasite (we had the blowfly
    with H5N1 in Japan) or the parasite transports the virus.
    These swans are permanently licking their feathers with
    some fat from a gland AFAIK. Well, that could explain why
    the feather-pluckers got it. I was also speculating
    that the non-migratory swans might have got it from geese
    through Freyana Anserina. But this is mere speculation
    at this point.

  11. #12 Marissa
    June 29, 2006

    Revere, there were several reports of a few wild birds on Prince Edward island that had “low-pathogenic” H5N1, but the later reports seem incredibly muddled and it’s hard to draw conclusions. I suspect sampling problems.
    I would not expect to see any migratory H5 transfer until the fall–that according to the discussions I’ve had with vet lab officials in my state.