August 4, 2006
Closer Study of H5N1 Strains Needed, Expert Says
By Tan Ee Lyn
HONG KONG -- A leading virologist has urged countries battling new H5N1 bird flu outbreaks in animals to analyze the genetic makeup of the virus to trace its origins and better arm themselves to combat the disease.
Although the H5N1 virus has killed 134 people since re-emerging in Asia in late 2003, it remains largely a bird disease. But experts fear it will mutate and gain the ability to spread efficiently among people, sparking a pandemic that could kill millions.
However, some hope that such a disaster might be averted if the disease can be effectively controlled in birds. Peiris said it was paramount now for Thailand to sequence the H5N1 virus that has recently re-emerged in the country's north and northeast after a nine-month hiatus.
"It will be very important to find out whether this new virus is the same virus that was there in Thailand before or whether it is a different virus that has been introduced," said Peiris, who was recently decorated for his work in fighting H5N1 and SARS.
Through sequencing a virus, scientists will know which other strain it is most closely related to. That helps epidemiologists trace the origin of an outbreak.
"If this virus is still the same old virus, it means you have to think of additional things to do to completely keep it under control. But if it is a Qinghai-like virus, then it means it comes from wild birds," he said, referring to Qinghai Lake in China, a breeding spot of a strain of H5N1 that has since spread to parts of Europe, Africa and India via migratory birds.
"Then in a sense, it is not that the measures they used were insufficient. You are talking about a different problem ... reintroduction from migrating birds."
If the virus in Thailand was found to be very similar to the ones in southern China, it "might point to smuggling," he said.
"It is molecular detective work ... I am sure Thai scientists will do this quickly. They have the capacity to do this."
Peiris said genetic sequencing was badly lacking in parts of Asia, but declined to say where. H5N1 is endemic in Indonesia, where it has killed 42 people, and has flared up in Laos. Vietnam fears a comeback of the virus -- which killed 42 people there -- after many months without cases in people or poultry.
Indonesian scientist Abdul Adjid said laboratories there have been conducting genetic sequencing. So far, they have sequenced the haemagluttinin protein, which is on the surface of the H5N1 virus, in about 40 to 50 animal samples.
"We see whether the virus is still highly pathogenic or not according to the HA (haemagluttinin) and compare (it with other strains) ... we found changes but not significant," he said, adding that these results have been published in local journals.
Peiris said the world risked losing vital information if sequencing was not carried out.
Such information included mutations showing if a particular strain might be evolving to become better adapted to humans and transmitting efficiently among them.
"There are some changes we look out for that might provide clues that the virus might be getting more potential to cross over to humans, for example, the receptor binding sites (in viruses) that lock on to human cells, that sort of information can come from systematic analysis of animal viruses," he said.
Avian flu viruses generally prefer to attach themselves to receptors in bird hosts, which is why it is rare for humans to catch bird flu.
However, some experts believe it is when avian flu viruses switch and adapt to receptors in humans that they will become easily transmissible among people.