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Human / Human H5N1 Transmission in Thailand?
The mother developed symptoms over a week after the daughter and the aunt had not been in contact with the chickens who had died (the mother had been with her daughter at the hospital before the mother was admitted to the hospital). This cluster is very similar to the cases in the Pham family in Hau Giang in southern Vietnam last month. An older sister who died did test positive for H5N1, but no samples were collected from her brother or cousin, both of whom also died a week earlier with similar symptoms. They too died around the time the older sister developed symptoms and media reports did not mention contact with sick birds.
Recent retrospective serum studies of the 2003 H7N7 outbreak in the Netherlands indicated that many contacts had become infected with H7N7 although most had mild symptoms or were asymptomatic. Thus, human / human transmission was possible in the absence of H1/H2/H3 or N1/N2.
Clearly more screening of contacts is warranted and alert levels should he heightened.