The H7N9 bird flu virus can be transmitted not only through close contact but by airborne exposure, a team at the University of Hong Kong found after extensive laboratory experiments.
Though the virus appears to have been brought under control recently, the researchers urged the Hong Kong authorities to maintain strict surveillance, which should include not only poultry but humans and pigs.
“We also found that the virus can infect pigs, which was not previously known,” said Dr Maria Zhu Huachen, a research assistant professor at HKU’s School of Public Health.
There have been 131 confirmed human infections, with 36 deaths, the World Health Organisation said. All but one of the cases was on the mainland. The virus appears to have been brought under control largely due to restrictions at bird markets and there have been no new confirmed cases since May 8.
But Zhu said that although there was no evidence of sustained human-to-human transmission, their study provided evidence that H7N9 was infectious and transmissible in mammals.
In the study, to be published today in the journal Science, ferrets were used to evaluate the infectivity of H7N9. It was found the virus could spread through the air, from one cage to another, albeit less efficiently.
Inoculated ferrets were infected before the appearance of most clinical symptoms. This means there may be more cases than have been detected or reported.
“People may be transmitting the virus before they even know that they’ve got it,” Zhu said.
Additional tests using pigs, a major host of influenza viruses, showed that they could also get infected with H7N9. Zhu warned that H7N9 may combine with pig viruses to generate new variants.
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