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    Experts debate whether eating infected poultry spreads avian flu virus


    Can people catch the H5N1 avian flu virus by eating infected poultry? Colin Blakemore, chief executive of the U.K. Medical Research Council, says the public need not worry.

    "There is no evidence of transmission to people by eating cooked eggs or chicken," he said on BBC radio last week, adding that the only food risk he could see was from "drinking swans’ blood."

    Blakemore’s sound bite came a day after Britain’s first case of H5N1 in a wild bird was confirmed in a dead swan found floating in a harbour in Cellardyke, Scotland. His advice echoes a slew of recent reassurances by governments worldwide and by the World Health Organization, all conscious of damaging public confidence in the poultry industry.

    But many flu scientists are concerned that, although the risks are low, there is not enough evidence to say that the virus cannot be transmitted by eating infected poultry.
    "Oral transmission is an open question," says Masato Tashiro, a virologist at the National Institute of Infectious Diseases in Tokyo. "Direct evidence of oral infection is lacking, but so too is proof against."

    On March 23, the European Food Safety Authority published a prominent scientific risk assessment. Its advice is that poultry products are safe to eat and have "not been implicated in the transmission of the H5N1 avian influenza virus to humans."
    H5N1 is present in the meat and eggs of infected birds, and animals have become infected by eating diseased birds. But the EFSA plays down this route in humans, arguing that "humans who have acquired the infection have been in direct contact with infected live or dead birds."

    That overstates the case, says Jody Lanard, a physician and risk-communication consultant based in Princeton, N.J., who recently advised the World Health Organization about pandemic communication. She points out that the report itself acknowledges frequent instances of insufficient epidemiological evidence to identify the source of infection. She adds that the report also says sources of infection such as poor preparation and cooking of food cannot be excluded.

    "Such cases could equally well indicate a likely gastrointestinal portal of entry," agrees Menno de Jong, a virologist at the Hospital for Tropical Diseases in Ho Chi Minh City, Vietnam.

    However, the report dismisses the idea that H5N1 can enter the body through the human gut, concluding that there is "no proof that virus replicates in the human intestine." Although the report mentions the presence of diarrhea in infected humans, together with the detection of viral RNA in intestines and of the virus in rectal swabs, it says these "do not allow one to conclude that the gastrointestinal tract is a portal of entry or a target organ."

    De Jong, who has treated many of the cited diarrhea cases, says the report’s authors are "formally right" to say there is no proof that the virus replicates in the intestine. But there is no proof that it doesn’t either, he says.