Sunday, May 15, 2005

Bird flu pot still simmers

At times news on the bird flu front is quieter than others, but we shouldn't be fooled. The pot is still simmering. Here are some reminders.

A 20 year old woman from Kampot province, Cambodia (on the Vietnam border) is on a respirator in a Vietnamese hospital. Dead chickens were reported in her neighborhood. Blood samples have been sent to Ho Chi Minh City for testing (The Star, Malyasia). Meanwhile Vietnam itself is reporting its first case in three weeks, a 52 year old man with a psychiatric disorder who collected dead chickens in his village to eat at home. His family had him committed to a mental hospital, where he developed fever and respiratory distress. He was hospitalized in Hanoi on April 6 and tested positive for H5N1 later (, Australia). Thus while this case has just been reported, it is over 6 weeks old.

In Indonesia, a warning sign of a different sort has appeared. An Indonesian university scientist decided to test 20 pigs being kept 100 yards from a chicken farm on Java, an area that had a bird flu outbreak last year.
"I found it in the snout to begin with, but I was doubtful whether this meant they were truly infected," he said in a telephone interview. "So I then proved it by finding a matching strain in the blood." (Chris Brummitt, by-line, AP in Houston Chronicle)
Last year reports from China of H5N1 infected pigs were greeted with skepticism in some quarters, but this report confirms the phenomenon.
A university scientist in east Java detected H5N1 virus in throat swabs and blood samples from a pig in Surabaya by RT-PCR (reverse transcriptase polymerase chain reaction). Inactivated RNA isolates have been sent to the Tokyo University, where 8 fragments (HA, NA, PA, PB1, PB2, M, NP, NS) were sequenced. Results showed that the virus was similar to the avian influenza virus from poultry, characterised by high pathogenicity (based on the study regarding the cleavage site). The gene for haemagglutinin of the isolated virus was more than 98 per cent identical to samples taken from infected Indonesian chickens and quail. The agriculture department will carry out sampling from several pig farms. (FAO via ProMed)
The pig issue is of some significance because swine have traditionally been considered the "mixing vessel" for pandemic flu. Bird and human receptors for influenza virus are different (NeuAc-2,3Gal in birds versus 2,6Gal in humans), but pigs have both receptors, allowing easier co-infection and the potential for reassortment of pig or human with avian viral genes or recombination of bits and pieces of genes from pigs or humans and birds. The result might be a bird-human virus chimera with both virulence for humans and easy transmissibility. The human cases of H5N1 to date seem to have come directly from birds without a pig intermediary, unlike previous avian viruses. Thus the significance of finding it in pigs, now, is unclear but is certainly not good.

The new cases in southeast asia and the discovery of swine infection in Java are further evidence the witches brew is still cooking.