Thursday, March 17, 2005

Bird flu miscellany

This is a miscellany of bird flu items from the last day or two. Most people who read this site are aware of these things as they read other sites. Here is my take.

The Journal of Virology has just published a paper by Nguyen et al. ("Isolation and Characterization of Avian Influenza Viruses, Including Highly Pathogenic H5N1, from Poultry in Live Bird Markets in Hanoi, Vietnam, in 2001," J Virol. 2005 Apr ; 79(7): 4201-12) that examines the genomes of the highly pathogenic poultry viruses circulating in Vietnam in October, 2001. Strains included H5N1, H9N2, H4N6, H5N2 and H9N3, collected from 189 birds and 18 environmental samples in live bird markets in Hanoi. I have only been able to see the abstract so far. Examination of the HA protein on the H5N1 viruses showed them to be similar to H5N1s isolated elsewhere in Asia during this period, suggesting that the viruses came from a common original source. But they were also genetically distinct from H5N1 viruses isolated in early 2004 during the most recent outbreak. Thus either the more recent virus comes from a different source or represents a mutated 2001 virus. The abstract does not indicate the nature of the genetic differences or the authors' interpretation, if any, of this. Meanwhile there is continued fretting over the lack of timely information provided to WHO and the international community by the Vietnamese authorities. New reporting procedures are allegedly in place that will remedy this. We'll see.

The case of the female nurse from the Red River Delta province of Thai Binh, initially thought to have bird flu but then reported as "testing negative," has not been further clarified with any official reports. There is some skepticism about the negative test, as false negatives have been common in Vietnamese testing. This is a matter of considerable importance as it bears on whether the case clusters are increasing in size (the Thai Binh cluster is already four and with this nurse would be five, the largest cluster yet reported).

Thanh Tien News (Vietnam) is now reporting a 5 year old boy from the northern province of Quang Binh hospitalized with fever and pneumonia. His 13 year old sister died 10 days after eating "a dead chicken" (sic) 3 weeks ago. His illness, if of recent onset, is 10 days after that, so human transmission is a distinct possibility. And SABC News (South Africa) reports that a death over the weekend of a male, age not given, is being investigated by Vietnamese authorities as due to bird flu. The patient was from the southern province of Kien Giang, the first death in the south in many weeks. Tissue testing was not complete, so we await further details on this case.

The Vietnamese are also considering poultry vaccinations, something now only done officially by China and Indonesia, although the Thais are planning to do it. There is some controversy about this as vaccination prevents birds from getting sick and probably decreases viral shedding, but also allows infection without visible symptoms, increasing the likelihood that the birds can infect other birds, or possibly people, although the latter has not been shown. to date there is little experience with H5N1 vaccination. There are unconfirmed reports of fresh outbreaks of avian influenza in poultry in North Korea (News24, South Africa) and Indonesia (Irish Examiner). Now South Korea is postponing a planned import of chicken for later this month.
A ministry [of Agriculture and Forestry] official said Tuesday it was waiting for confirmation of rumors that a high-ranking North Korean official who defected to the South spoke of an outbreak of avian influenza in the reclusive country. It asked the Unification Ministry to confirm the validity of the rumours through communication with the North, and failing this, will take preventative measures against the deadly virus, he said.
Thus the disease is firmly entrenched in Asia, providing the ingredients for the kind of genetic shift that emerges periodically as pandemic influenza. The H5N1 strain has already mutated considerably, increased its host range to infect mammals including humans, and is remarkably virulent.

Bottom line: no good news to report.