Scientists confirm new H7N9 bird flu has come from chickens

By Kate Kelland

LONDON (Reuters) - Chinese scientists have confirmed for the first time that a new strain of bird flu that has killed 23 people in China has been transmitted to humans from chickens.

In a study published online in the Lancet medical journal, the scientists echoed previous statements from the World Health Organization (WHO) and Chinese officials that there is as yet no evidence of human-to-human transmission of this virus.

The H7N9 strain has infected 109 people in China since it was first detected in March. The WHO warned on Wednesday that this strain is "one of the most lethal" flu viruses and is transmitted more easily than the H5N1 strain of bird flu, which has killed hundreds around the world since 2003.

Kwok-Yung Yuen of the University of Hong Kong, who led the study, said its findings that chickens in poultry markets were a source of human infections meant that controlling the disease in these places and in these birds should be a priority.

"Aggressive intervention to block further animal-to-person transmission in live poultry markets, as has previously been done in Hong Kong, should be considered," he told the Lancet.

He added that temporary closure of live bird markets and comprehensive programmes of surveillance, culling, biosecurity and segregation of different poultry species may also be needed "to halt evolution of the virus into a pandemic agent".

"The evidence ... suggests it is a pure poultry-to-human transmission and that controlling (infections in people) will therefore depend on controlling the epidemic in poultry," he said.

Yuen's findings do not mean all cases of human H7N9 infection come from chickens, or from poultry, but they do confirm chickens as one source.

The WHO has said 40 percent of people infected with H7N9 appear to have had no contact with poultry.

Other so called "reservoirs" of the flu virus may be circulating in other types of birds or mammals, and investigators in China are working hard to try find out.

CASE STUDIES

Yuen's team conducted detailed cases studies on four H7N9 flu patients from Zhejiang, an eastern coastal province south of the commercial hub Shanghai.

All four patients had been exposed to poultry, either through their work or through visiting poultry markets.

To find out whether there was transmission of the virus from poultry to humans, the researchers took swabs from 20 chickens, four quails, five pigeons and 57 ducks, all from six markets likely to have been visited by the patients.

Two of the five pigeons and four of the 20 chickens tested positive for H7N9, but none of the ducks or quails.

After analysing the genetic makeup of H7N9 virus in a sample isolated from one patient and comparing it to a sample from one of the chickens, the researchers said similarities suggest the virus is being transmitted directly to humans from poultry.

The team also checked more than 300 people who had had close contact with the four patients and found that none showed any symptoms of H7N9 infection within 14 days from the beginning of surveillance. This suggests the virus is not currently able to transmit between people, they said.

But they noted that previous genetic analysis shows H7N9 has already acquired some gene mutations that adapt it specifically to being more able to infect mammals - raising the risk that it could one day cause a human pandemic.

"Further adaptation of the virus could lead to infections with less severe symptoms and more efficient person-to-person transmission," the scientists wrote. (Editing by Kevin Liffey)

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Finding Another Earth: How Will Scientists Confirm It Exists?

LONG BEACH, Calif. — The announcement this week that astronomers have found a potential alien world that could be the most Earth-like exoplanet yet is raising a big question: How will scientists confirm the existence of a true alien Earth?

While NASA's planet-hunting Kepler space telescope, which discovered the newfound Earth-like planet candidate KOI 172.2, is great for finding large numbers of exoplanets, it is not our best bet for characterizing an Earth twin circling a distant star, researchers say.

In order to understand what an "alien Earth" candidate really looks like, it takes a more refined approach than what Kepler can provide at the moment.

"It’s a statistical mission," Kepler deputy science team lead Natalie Batalha said at the 221st meeting of the American Astronomical Society on Tuesday (Jan. 8).

The Kepler mission is designed to find out how many possible exoplanets there could be in any given part of the galaxy. The space telescope launched in 2009 and stares unblinking at a single patch of the sky to scan for dips in light from stars, a telltale sign of an orbiting planet passing in front of the star. Kepler's observations can tell scientists where a planet is in relation to its home star, but the spacecraft has little to add about important details such as an exoplanet's climate, researchers said. [Most Earth-like Exoplanet Discovery Explained (Infographic)]

But how can scientists study those important questions that need to be answered before a planet can be deemed a true Earth twin?

Finding Earth’s twin

The Kepler mission is a starting point in the search for a true Earth-like planet, Nicolas Cowen a postdoctoral fellow in astronomy at Northwestern University in Evanston, Ill. told SPACE.com. "Kepler just told us how big the telescope we have to build is."

There could be more than 17 billion Earth-sized planets in the Milky Way galaxy alone, but that doesn’t mean they’re easy to research once detected. Once planets of interest are confirmed by Kepler, then other instruments can be used to investigate the specifics of the planet.

A ground-based telescope could be just the right tool for finding Earth’s twins, said Cowen. If the exoplanet in question is near enough to the Earth and in exactly the right position, researchers could aim a 10-meter (33 foot) dish toward the planet to optically observe its transit between the Earth and its home star. After researchers have measured the radius of the planet, and if a telescope can make direct observations of the planet in question, Cowen said, then it is just a matter of patience.

Cowen added that all it takes after a researcher knows the size and rotation of the planet is as much observation time as possible. Watching the way a planet rotates and taking measurements of the different colors that come in and out of view as the planet orbits its star gives researchers a sense of what might lie under the surface of the atmosphere.

Water, land and clouds reflect light in different ways, and by directly observing those reflections, astronomers like Cowen can start to see how an exoplanet might be an Earth twin.

“That’s what would happen in an ideal world,” Cowen said.

Closer than we think?

Those days of "ideal" research might not be as far off as some believe. Cowen thinks that it could only be a matter of time before astronomers are able to peer into the atmosphere of an exoplanet and see what’s happening on the surface using a ground-based telescope.

In a presentation earlier this week, astronomer Ian Crossfield suggested that it’s likely that an Earth-size planet in the “habitable zone” of an M-dwarf star — a type of star smaller and dimmer than the sun, but plentiful in the Milky Way — will be found within 31 parsecs of Earth, a relatively short distance in astronomical terms.

“This is the first meeting where any of these ideas have even brought up,” Cowen said. “It’s very exciting.”

You can follow SPACE.com staff writer Miriam Kramer on Twitter @mirikramer. Follow SPACE.com on Twitter @Spacedotcom. We're also on Facebook & Google+. 

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