7th Confirmed Fatal Bird Flu Case in Vietnam
Recombinomics Commentary
January 21, 2005
>> Further testing has shown that a dead man from Vietnam's northern Thai Binh province had been infected with bird flu as his alive younger brother, local newspaper Labor on Friday quoted the National Hygiene and Epidemiology Institute as saying.
"The third testing by our institute showed that samples from the 47-year-old patient Nguyen Huu Viet were positive to H5N1,"said Institute Director Nguyen Tran Hien, noting that samples from his 42-year-old brother named Nguyen Thanh Hung were earlier tested positive to the bird flu virus.
Viet had been looked after by Hung, who lived in Hanoi before he died on Jan. 9 at the Tropical Disease Institute in the capital.
"H5N1 spreading from persons to persons is merely hypothetical. It can't be concluded that this is a human-to-human transmission case," the director noted.
Two previous tests indicated that Viet had not been infected with H5N1. On the contrary, the first testing on samples from Hung showed that the younger man had not contracted the virus, but the two following tests proved that he is a bird flu victim. <<
The above report describes the 7th confirmed fatality in Vietnam. The 8th fatality has not yet been confirmed. The number of suspect cases continues to rise in the north and south, including the brother of the two confirmed H5N1 cases in the north.
The three generations of confirmed or suspect bird flu is a concern. The index case (47M) died on Jan 9. However, it took three tests to confirm H5N1 and confirmation was 11 days after his death. The suspicion level was high because of prior exposure to dead chickens and symptoms in his caretaker, his brother (42M). His brother was admitted on Jan 13 and took 6 days to confirm. The initial test was also negative, but the suspicion level was high because his older brother had died of acute pneumonia. The younger brother did not have reported contact with infected poultry.
On Jan 20 a third brother was hospitalized as a suspect case. If he is confirmed he will be the third generation of transmission.
The difficulty in verifying H5N1 in the first two cases of this cluster is a concern. Although both confirmed cases had pneumonia, it is not clear that there would have been repeated tests had not the two been linked. This situation is analogous to an earlier cluster in Vietnam. In that cluster a brother and cousin developed fatal infections with bird flu symptoms. They were cremated before samples could be collected. However, the older sister subsequently developed symptoms and initially tested as negative. Since the suspicion level was high due to the connection with the two earlier fatal cases she was retested and found to be H5N1 positive. Sequence analysis of HA and NA from two chickens from the same province isolated at about the same time, A/chicken/Viet Nam/HauGiang-178/2004(H5N1) and A/chicken/Viet Nam/HauGiang-617/2004(H5N1) indicated they were similar to virus isolated in Vietnam earlier in the year.
Another cluster was identified in Thailand earlier this year. The 9 year old index case was initially diagnosed as having dengue fever. Therefore her mother was allowed close contact in the hospital. After the death of the index case, the mother and aunt developed symptoms. The aunt is the only recent bird flu survivor in Thailand. Sequence analysis of HA and NA of the recovered sequences, A/Thailand/Kamphaengphet-Nontaburi/04(H5N1), from fixed tissues, indicated that the fatal infections were from H5N1 similar to isolates collected earlier in the year
Sequence information on the latest cluster in Hanoi would be useful. Analysis of sequences from H5N1 infected grey herons in Hong Kong last month identified novel genes which are almost certainly recombinant genes. Recombination can lead to a broader host range as had been seen in Vietnam and Thailand last year. New genes can also be more difficult to detect using assays based on earlier isolates.
The difficulty in detecting H5N1 in the first two confirmed avian influenza cases in northern Vietnam raises serious questions about the true level of human and animal infections (poultry and pets) in Vietnam.
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