A 26-year-old woman in Thailand who died of avian influenza earlier this month probably contracted the disease from her daughter, researchers and Thai officials announced today. So far, World Health Organization (WHO) scientists are cautiously optimistic that this is not the start of a major outbreak.
Researchers say the woman, who lived in the Bangkok area, had returned to a rural village in northern Thailand to care for her sick daughter. The girl was living with her aunt and probably contracted the virus from local chickens. She was cremated before researchers could collect tissue samples that could confirm her illness. But tissue samples from the mother proved positive for H5N1. So far, says WHO virologist Klaus Stöhr, Thai authorities have detected no increase in respiratory disease among villagers or health workers who cared for the patients. However, the aunt and her son have also been sick and are being investigated as possible cases of human-to-human transmission.
Limited human-to-human transmission of bird flu has been documented in the past. This cluster, too, appears to be a case of "nonsustained, dead-end transmission," Stöhr says, that doesn't pose a larger threat. But the worst scenario--that the virus has mutated to a more dangerous form that could trigger a pandemic--cannot be definitively ruled out until the WHO collaborating center in Atlanta analyses the new samples from Thailand later this week.
Meanwhile, several global health groups are calling for greater vaccination of Southeast Asia's poultry flocks in a bid to corral the dangerous virus. To keep the virus in check, governments should be vaccinating and not just culling poultry flocks, the United Nations' Food and Agriculture Organization (FAO) and the World Organisation for Animal Health said in a 28 September statement. "It has been shown that the use of such vaccines does not only protect healthy birds from disease but also reduces the load of viruses excreted by infected birds and thus the likelihood of transmission of the virus to other birds and to humans," according to the statement.
China and Indonesia already have vaccination programs. But Thailand and other nations do not, in part because poultry exporters fear importing countries will ban products from vaccinated birds, which don't exhibit flu symptoms but can still carry the virus.