(HealthDay News) – A bird flu virus, which is not normally transmissible between humans, can be made transmissible between ferrets by mutations and combination with genes from a human pandemic swine flu virus, although the reassortant H5 hemagglutinin (HA)/H1N1 virus is not highly pathogenic and does not cause death.

To examine what molecular changes would be needed to produce an avian H5N1 influenza A virus that was transmissible between mammals, Masaki Imai, from the University of Wisconsin in Madison, and colleagues created a virus with four mutations in H5 viral HA, which is used to bind to the host, and the seven remaining gene segments from a 2009 human pandemic H1N1 virus.

The researchers found that, in a ferret model, this virus could be transmitted via respiratory droplets. However, although the virus replicated efficiently and preferentially recognized human-type receptors, infection was associated only with lung lesions and weight loss but was not highly pathogenic and did not cause death.

“These results indicate that H5 HA can convert to an HA that supports efficient viral transmission in mammals; however, we do not know whether the four mutations in the H5 HA identified here would render a wholly avian H5N1 virus transmissible,” Imai and colleagues conclude. “The genetic origin of the remaining seven viral gene segments may also critically contribute to transmissibility in mammals.”

Several authors disclosed financial relationships with pharmaceutical and biotechnology companies.

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