Transmission of Avian flu in "close family environments" may occur more often than has previously been thought, according to a study conducted by the Centers for Disease Control and Prevention, health officials from several Southeast Asian countries and agencies such as the World Health Organization. "Clusters" of human Avian flu infections have been studied since 2003.
From today's Wall Street Journal (subscription required):
The best-documented case of a cluster involved a Thai woman who was apparently infected in 2004 after she left her factory job in Bangkok to return home to her village to care for her H5N1-infected daughter. Both later died from the virus.
Sonja Olsen, acting director of the CDC's International Emerging Infections Program with the Thai government in Bangkok, says the quality of data in that particular cluster was unusually good. "That's why we can say it was most likely person-to-person transmission," she says.
More cases have been identified:
In their study, published in the CDC's Emerging Infectious Diseases journal this month, they identified at least 14 other possible instances involving clusters of at least two people, most often family members, dating from December 2004 to July 2005.
In three of those infection clusters, in Vietnam, seven days passed between the onset of symptoms in the first and second patients. This makes simultaneous acquisition of the virus from a common source unlikely, Dr. Olsen and her co-authors say. And in another case, a Vietnamese nurse contracted the disease from an H5N1-infected patient.
According to the article, many experts believe that a pandemic could begin with 20 or more clusters of Avian flu breaking out in one area.
