Sunday, January 23, 2005

Bird flu tsunami headed this way?

Since Bouphonia has done us the honor (and saddled us with the responsibility) of keeping the blogosphere updated regarding bird flu, we report the latest news. It is not reassuring.
  • There is another confirmed bird flu death, a 35 year old woman from the Mekong Delta (South). Add this to the death of a 17 year old boy in the North and the total is nine deaths since the end of December.
  • The 22 year old sister of the deceased teenage boy is now ill. H5N1 illness has not been confirmed (but see next), nor is it yet known if she cared for her brother when he fell ill. But as reported in a recent post here there is already disquieting evidence of secondary person-to-person transmission in the case of the 42 year old who cared for his (now deceased) 45 year old brother. Now comes news that a third brother, 36 years old, has been hospitalized. While all three shared a common meal of blood pudding made from ducks and pigs, they did not become ill simultaneously but at intervals of nine days each. This argues strongly for person-to-person transmission, in this case over three (viral) generations, a possible indication that human infection is becoming more likely.
Update (1/26/05, 10 pm EST): CIDRAP now reports that WHO now says (contrary to the WHO post of earlier in the day) the third brother was hospitalized only for observation and is not a case. This means this is a single person-to-person transmission of one viral generation similar to the recently reported Thai cases (see post, The New England Journal's bird flu articles, link in sidebar)
  • The disturbingly high case-fatality rate (in excess of 70% so far) continues. Viet Namese health authorities are also describing the severe respiratory distress syndrome as becoming "more complex." Henry Niman at Recombinomics suggests this may be evidence of further genetic changes in the virus.
  • Cases initially described as negative for H5N1 (the two brothers mentioned above being examples) were subsequently confirmed as positive for the virus. Niman suggests (here and here) this, too, may be evidence of a mutating virus. He makes the following important argument. Influenza A viruses have two ways to change their genetic composition, reassortment and recombination. Most of the attention has been on reassortment. The virus is unusual in that its eight genes are in separate segments. If there is co-infection with a human influenza virus, these segments can mix and match ("reassort"), to produce a virus where some of the genes can come from H5N1 and some from (say) a human H1N1. But the individual segments (genes) can also recombine "internally," so that the H5 gene from the bird can acquire some of the characteristics of the H1 gene from humans (such as being able to attach readily to human lung cells), but still look to the immune system like an H5 virus, to which we have no pre-existing immunity. A recombination affecting the H5 gene in the bird virus might be the reason that initial tests fail to confirm the disease. An H5 recombined gene, while still H5, now "looks different" to the initial tests, which are based on antibodies to an unrecombined H5.
  • As reported here, the disease among poultry continues to spread exponentially in Viet Nam. New data confirms this:
The Ministry of Agriculture and Rural Development reported on Saturday that bird flu has spread to 232 communes in 23 cities and provinces nationwide, with more than 500,000 chickens, ducks and quails being culled. After Hanoi and Ha Nam, Hai Duong is the third locality in the northern region to be affected by bird flu . . .
  • Thailand is now reporting more disease, this time including fighting cocks and chickens.
WHO remains cautious in its interpretation of these events, noting that "sporadic" human cases would be expected in an area where the disease among poultry is so widespread. But those on the spot are less hesitant (Business Day via Bloomberg):
“There is a real danger to let this wave wash away what may turn out to be a bigger problem for the country if we have an avian flu pandemic,’’ WHO representative to Thailand William Aldis told reporters in Bangkok. “The situation in Vietnam has given us all a bit of a shock.’’
So there you have it. A viral tsunami. But this time it won't "only" affect eight countries. If ever there was an issue of "Homeland Security" this is it. If this virus were a terror suspect, on the basis of public health intelligence we would be on Red Alert. They are going to blow it again.

NB: Henry Niman at Recombinomics does an excellent job of tracking developing events, although much of his commentary is technical in nature. Recommended for professionals and technically confident laypersons.