Human Transmission in Cambodian Bird Flu Cluster
Recombinomics Commentary
March 4, 2005
>>Relatives say the teenager gathered birds that had dropped dead, plucked them and prepared them for the farming family's meal. Cooking would kill any germs, but handling carcasses is risky. Oi Chanda, a cousin, said that a few days later, the youth fell ill, developing a fever and coughing violently. He died 10 days after getting sick. "We were shocked that he died so quickly," Ms. Chanda says. "He was a very healthy boy."
It's not clear whether Tit Chiang contracted bird flu. His body was cremated soon after his death according to Buddhist custom. That means no tests could be conducted to determine whether he was infected by the virus. Cooked meat isn't considered a risk, but handling sick birds is.
Dr. Sovann and WHO investigators have since concluded that Chiang's sister, Ms. Sokhan, was in close contact with his body. Several days after the teen was cremated, Ms. Sokhan also fell ill. "One theory is that she caught the virus while crying over her brother's body and preparing it for cremation," says Dr. Miller at the WHO. "But we don't really know because we couldn't test her brother."
As Ms. Sokhan's sickness worsened, her relatives took her to a nearby medical clinic. But staff there didn't know anything about bird flu and sent her home with instructions to perform a ceremony to appease the angry spirits of her ancestors.
"She performed the ceremony, but it didn't seem to make any difference. She was still sick," says Kheam Phon, Ms. Sokhan's aunt.
She decided to take her niece to a hospital in Vietnam, in the hope of getting better treatment. But it was too late. On Jan. 30, 12 days after her brother died, Ms. Sokhan also died. Tests performed by Vietnamese authorities revealed she had the H5N1 virus. <<
The detailed description of the Cambodian cluster matches the other familial clusters in Vietnam and Thailand. Disease onset is bimodal. One or two weeks after the index case develops symptoms a family member develops the same symptoms. The index case dies, but because there were no samples collected for testing, the index case is not an official case.
H5N1 is detected in the family member, but since the index case was not tested it is not an official cluster, and the official comment is that it might be human-to-human transmission, but it is not certain.
Although transmission in the familial clusters cannot be certain, especially when each cluster is viewed individually, the bimodal nature of the onset dates strongly suggests human-to-human transmission. When 11 of 11 clusters have a bimodal distribution of onset dates, there can be little doubt that human-to-human transmission is happening, and the lack of a warning concerning such transmissions increases the likelihood that similar transmission will happen in the future.
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