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Vietnam Confirms Evolving H5N1 Creates False Negatives
June 25, 2005
>> State-run media cited a ministry report as saying laboratory test results overseas and at home showed the antigen structure of virus is changing.
"The ministry warned in the report that the mutation of the H5N1 virus is raising the possibility of infections on humans, because the test results of international and domestic laboratories showed the virus's antigen structure contained a change," the Saigon Giai Phong (Liberation Saigon) daily said.
The mutation of the virus explains why Vietnam did not detect major outbreaks in poultry in recent months but people still fell sick of avian influenza, it said. <<
The above comments confirm earlier reports of false negatives in northern and southern Vietnam. As H5N1 evolves primers that target the earlier sequences may not detect an altered version. Similarly, vaccines that target an early version may not be as effective against a later version because of additional recombination. The current pandemic vaccine in clinical trials targets two isolates from 2004 which are virtually identical to each other, but different than the 2005 isolates in northern and southern Vietnam.
The comments by government officials are also consistent with the reported positives on the western blots. This data was generated using 1000 serum samples from birds and people in northern Vietnam. There were several large clusters of cases in Quang Binh in central Vietnam and Thai Binh, Haiphong, and Qunag Ninh in northern Vietnam that appeared to involve increased human-to-human transmission. The serum were reported to have been sent to the CDC in Atlanta in April, but the results were not made public even though an urgent meeting was held in Manila on May 6-7. Recent comments from WHO suggest that the samples were not sent and a confirmatory HI test have not been run because Vietnam lacks the necessary BL-3 lab facilities. These comments are quite remarkable because it was quite clear in March that these larger cluster, if positive for H5N1, would move the pandemic from phase 4 to phase 5, and possibly phase 6.
Media reports suggest that these changes set the stage for the explosion in admissions this month in northern Vietnam. These patients, which have a milder disease, also have sore throats, suggesting the new H5N1 can more efficiently infect the upper respiratory tract, which could result in more efficient human-to-human transmission.
Thus, H5N1 evolves as WHO issues press releases indicating that the warnings revealed by the western blot data are just "research" results.
Unfortunately, H5N1 appears to be researching humans more than humans are researching H5N1.