Bird Flu Fatality Rate in Cambodia and Mekong Delta Is 100%
Recombinomics Commentary
April 22, 2005
>> A 20-year-old Cambodian woman who died in Vietnam this week was killed by bird flu, taking the death toll in Asia to 52, a health official said on Friday.
The woman died just hours after being rushed to hospital on Tuesday in Vietnam's southern province of Kien Giang, suffering from high fever and respiratory problems, a doctor who treated the woman told Reuters.
"This case has tested positive," said a Ho Chi Minh City official, who declined to be identified, following tests on samples from the woman at the city's Pasteur Institute. <<
The case above is the 5th fatal bird flu case in Cambodia. Four have been confirmed. The first reported Cambodian case was the brother of the first confirmed case. Like the case above, the first confirmed case sought treatment in Kien Giang in Vietnam, where H5N1 was confirmed and the patient died. All five cases in Cambodia were in Kampot, which is adjacent to the Mekong Delta region in southern Vietnam. This season all confirmed H5N1 cases in southern Vietnam have also been fatal
In marked contrast, most of the H5N1 cases in northern Vietnam have survived. The case fatality rate in the north is about 20%. Indeed a family of five tested positive for H5N1 and all family members recovered. Thus, in the north the clusters are larger, demonstrating more efficient transmission to humans. However, these are milder cases and the number of H5N1 infections is large. In the central highlands on commune in Quang Binh had almost 200 members ill with flu-like symptoms. In one family there was a death, and an H5N1 confirmed sibling who survived. Most of the commune members survived and although hundreds of samples were collected from people and poultry, the test results have not been made public, suggesting widespread infections by H5N1. Vietnam has sent up to 1000 samples to the CDC in Atlanta for further analysis.
Thus, there appears to be co-circulation of two strains of H5N1 in Vietnam. In the north transmissibility to humans in more efficient, but cases are milder. In the south the size of the clusters are smaller, but the cases in Vietnam and Cambodia have a case fatality rate of 100%. Co-circulation of these two strains can lead to further recombination, especially since 71% of the ducks in the Mekong Delta's 11 provinces are H5N1 positive.
The genetic instability of H5N1 and large animal reservoir in Vietnam are clearly cause for concern.
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