Karen Weintraub

Special for USA TODAY

Harvard and Yale researchers called Tuesday for an end to animal research into bird flu, worrying that the virus could escape and trigger a global epidemic.

Marc Lipsitch, a professor of epidemiology at the Harvard School of Public Health in Boston, said he doesn't think the rewards of creating a novel strain of avian flu in ferrets – as a few labs around the world do – justify the risk that the virus might escape and wreak havoc.

"There really are a lot of things we can and are doing that are much more likely to yield benefits and also don't put anyone at risk," he said. "We should support safe and effective research rather than risky research."

Mistakes have happened before, said Lipsitch, who co-wrote an opinion piece in the journal PLOS Medicine with Alison P. Galvani, an epidemiologist at the Yale School of Public Health in Connecticut. There is some evidence that a strain of flu common since the late 1970s was released from a lab in China or Russia, he said.

Even routine strains of the flu cause about 50,000 American deaths a year, according to the U.S. Centers for Disease Control and Prevention. Scientists worry about a strain that might be significantly more lethal, such as the 1918 flu, which killed 675,000 in the USA.

The H5N1 bird flu is routinely found in wild birds and sometimes in poultry. The virus occasionally jumps to people – usually after direct contact with infected or dead poultry – and 650 human cases of H5N1 have been reported from 15 countries since 2003, more than half of them fatal.

Individual errors are rare in any year or lab, Lipsitch said, but the risk adds up over time. If 10 laboratories did bird flu research with the level of precautions similar to that practiced today, there would be a 20% chance of the virus infecting a lab worker and a 1% chance of it escaping the lab within a decade, their research concluded.

Researchers who study bird flu disagreed with Lipsitch's conclusions. The science leads to an understanding of the flu that would not be possible through a different approach, said Yoshihiro Kawaoka, a virologist at the University of Wisconsin-Madison and at the University of Tokyo.

Before his research, Kawaoka said, others thought the H5N1 strain could not cause widespread illness, but his work in ferrets showed that it could and that countries should be stockpiling vaccines against it.

"This is a critical point since vaccines expire, and decisions by policymakers as to whether we continue to stockpile H5N1 vaccines should be based on scientific facts," Kawaoka said via e-mail. "Thus, human populations have already benefited from the H5N1 ferret transmission experiments."

Wendy Barclay, a virologist at Imperial College in London, said she has no concerns about the careful work done by Kawaoka and his colleagues but said Lipsitch correctly notes that not all researchers around the world are as meticulous.

"Even in the Western world, standards of health and safety are not uniform," she said, suggesting that global standards may be needed to control research into potentially dangerous viruses.

Overall, she said, there is no reason for people to worry about research projects: "I would not suggest that living next door to one of these labs increases your risk in any sense."