H7N9 Is More Adapted To Spread Among Humans Than Other Bird Flu Strains

beijing bird flu h7n9 girl patientA girl, who was previously infected with the H7N9 bird flu virus, waves as she is being transferred to a public ward from the ICU at Ditan hospital in Beijing, April 15, 2013.

Close contact with someone infected with the new bird flu strain, H7N9, is likely to get you sick, according to a new study published today, May 23, in the journal Science.

The virus isn’t that great at passing through the air, though, so in order to contract the virus you would need to stand and talk with the sick person for about 15 minutes.

Currently, 131 people have gotten sick with the new virus, and 36 have died. Hong Kong researchers are guessing that 90 to 120 more cases could exist, though cases have slowed in recent weeks.

“This study was designed to give us clues about the transmission of H7N9 which has affected some humans in China,” study researcher David Kelvin, of the University of Toronto, said in a statement.

That study included infecting ferrets with the virus in the lab. They use ferrets as the animal model for human flus because they are mammals like us, they get the same viruses, and they show symptoms of the infection.

They also tested the virus on pigs, because they are often incubators for influenza viruses. It didn’t pass between them as well as it did in the ferrets, though.

“The animals used in the study had very mild clinical symptoms as a result of their exposure to the virus and it was clear that very close contact was required for transmission. It also appears that this virus in its present form does not transmit very well through the air.”

Scientists are worried that it could mutate and gain that ability, since it’s already more evolutionarily adapted to spread among humans than other bird flus they’ve seen. They’ve already started seeing changes to the molecules on the outside of the virus that control how it enters cells, according to NPR’s Shots blog.

“These findings suggest that the novel virus had been evolving and might, with a few amino acid mutations, adapt to humans,” write the authors of the report in the New England Journal of Medicine, published May 22.

These “stepwise” adaptations — where small mutations happen over time — are similar to the way the 1918 and 1957 flu viruses adapted and caused pandemics. These mutations happen as the virus lingers in animal populations. Though there are fewer new human cases, the virus needs to be wiped off the face of the Earth, and quickly.

“There’s a bit of a worry in my mind that the urgency to do something about this will drop,” study researcher Richard Webby, of St. Jude Children’s Hospital and the Word Health organisation, told Shots. “We really need to get on top of this virus and get it out of animal populations. Otherwise it’s just not going to go away.”

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