Kawaoka says mutant H5N1 not lethal

Yoshihiro Kawaoka, a researcher at the University of Wisconsin-Madison and the author of a controversial mutant H5N1 study, said that there are key differences between his study and another controversial study in the Netherlands.

Kawaoka and Ron Fouchier of the Erasmus Medical Center in the Netherlands were each involved in research studying the transmission of potentially lethal H5N1 avian flu between mammals. The National Science Advisory Board for Biosecurity recommended on December 20 that reports on the two studies should withhold data that could allow others to replicate the studies, CIDRAP News reports.

Kawaoka's team fused the hemagglutinin gene from an H5N1 strain with genes from the 2009 H1N1 virus to create a virus that could spread but was not lethal.

"We identified a mutant H5 HA/2009 virus that spread between infected and uninfected ferrets...in separate cages via respiratory droplets in the air," Kawaoka said, according to CIDRAP News. "Thus viruses possessing an H5 HA can transmit between mammals."

This differs from Fouchier's study, which involved spreading a mutated H5N1 strain directly from ferret to ferret, which killed the ferrets in all cases.

"Our results also show that not all transmissible H5 HA-possessing viruses are lethal," Kawaoka said, according to CIDRAP News. "In ferrets, our mutant H5 HA/2009 virus was no more pathogenic than the pandemic 2009 virus - it did not kill any of the infected animals. And, importantly, current vaccines and antiviral compounds are effective against it."

Kawaoka is one of 39 influenza researchers who voluntarily agreed to a 60 day moratorium on research of H5N1 transmission so that more issues can be discussed. He stressed the importance of the research he and other researchers are doing on the subject.

"A subset of these mutations has been detected in H5N1 viruses circulating in certain countries," Kawaoka said, according to CIDRAP News. "It is therefore imperative that these viruses are monitored closely so that eradication efforts and countermeasures (such as vaccine-strain selection) can be focused on them, should they acquire transmissibility."

Flu experts said that while the controversial studies have value, the world's limited flu surveillance capabilities may not lead to immediate results.

"That claim is meeting with skepticism, however," Declan Butler, a reporter for Nature, said, according to CIDRAP News. "More than a dozen flu experts contacted by Nature say they believe that the work opens up important vistas in basic research, and that it sends a valuable warning about the potential for the virus to spark a human pandemic. But they caution that virus surveillance systems are ill-equipped to detect such mutations arising in flu viruses. As such, work on the viruses is unlikely to offer significant, immediate public-health benefits, they say."