BANGKOK, Nov. 23 (UPI) -- International researchers say the spread of avian flu from person to person may be more common than thought, but have insufficient conclusive evidence.
The best-documented case of a cluster of human infections involved a Thai woman who was 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, the Wall Street Journal said.
Investigators from the Atlanta-based Centers for Disease Control and Prevention, along with health officials from several southeast Asian countries have been closely following such clusters since the H5N1 strain of avian influenza first appeared in the region in 2003.
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.
However, World Health Organization officials say there is still no evidence that the virus has acquired the ability to easily pass from one human to another and that sick birds are responsible for the vast majority of infections.