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Research Snapshot: Confirming airborne transmission of influenza A virus in swine

It’s long been believed that, as in people, airborne transmission can be responsible for outbreaks of the flu virus in swine. Now, University of Minnesota researchers have helped shift such belief to scientifically-proven fact.

In a new study published today in the open-access online publication PLoS ONE, researchers from the University of Minnesota’s College of Veterinary Medicine (CVM) document the detection and isolation of airborne flu virus at four acutely infected pig farms. Furthermore, they demonstrate the airborne nature of the virus by confirming the presence of virus in air samples from inside swine barns, at the barn’s external exhaust fans and downwind from the farms at distances up to 1.3 miles away.

The research should help improve the design of flu control strategies (such as biosecurity containment systems) and strengthen research into the prevention of zoonotic infections.

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Health Talk Recommends: A more transparent battle with bird flu

Imagine a virus that could infect — and jump to and from — birds or mammals that is always adapting and changing, so by the time researchers have an answer for one strain, it’s already changed forms.

The virus, of course, is influenza.

In an editorial in the Washington Post, the editorial board explores H7N9, the most recent strain of avian influenza (bird flu). The board writes:

“This variant, known as H7N9, has not reached U.S. shores, but it is a reminder of the unpredictable nature of influenza. It might cause a pandemic, or settle into a slow burn for years, or simply die out. At this stage, no one knows. The uncertainty ought to remind us of past lessons about infectious disease and globalization, which remain as urgent as ever.”

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With swine flu cases on the rise, one U of M expert calls for a Swine Barn closure

Last week, Health Talk highlighted new research from Jeff Bender, D.V.M., an associate professor of veterinary public health in the University of Minnesota’s College of Veterinary Medicine, that found nearly 20 percent of seemingly healthy pigs at the 2009 Minnesota State Fair were carrying the influenza virus, and at least four were carrying the virus responsible for 2009’s swine flu pandemic.

This week, as nearly 1,000 pigs are scheduled to arrive at the Minnesota State Fairgrounds for the 2012 state fair beginning Thursday, swine flu has again captured national headlines.

Across the country, nearly 200 people in eight states have contracted the latest virus strain, H3N2v.  Yesterday the Minnesota Department of Health confirmed that the new strain of flu is now present in Minnesota.

Now, the situation has led one prominent School of Public expert to call for a closure to the Minnesota State Fair Swine Barn to protect the public from the virus.

In an article in today’s Star Tribune, Mike Osterholm, Ph.D., M.P.H., said the number of swine flu infections as a result of pig-to-human contact is unprecedented.  As a result, he believes the safest course is to simply eliminate that contact where you can.

The Star Tribune’s Maura Lerner reports:

On Monday, the CDC recommended that anyone who’s sick, or particularly vulnerable to the flu, avoid the swine exhibit. That includes young children, the elderly, pregnant women and people with severe chronic conditions.

Fair officials say their veterinarians will be closely monitoring pigs for signs of illness.

But Osterholm, a former Minnesota state epidemiologist, said the precautions may do little if any good at preventing the spread of the virus.

“As the pigs are being affected, so are the people having contact,” he said. “None of us have ever seen this kind of dynamic transmission from humans to animals,” he said. He also said there’s evidence that healthy-looking pigs can carry the virus.

“If ever we should be avoiding the human-animal interface, this is it,” he said.

Stay tuned to Health Talk for updates around H3N2v and any changes to Minnesota State Fair attractions as a result of swine flu.

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U of M researchers find even seemingly healthy pigs can be carrying influenza

It might sound strange, but transmission of the flu between humans and pigs is not just possible – it can be quite common.

Now, Jeff Bender, D.V.M., an associate professor of veterinary public health in the College of Veterinary Medicine and director of the Center for Animal Health and Food Safety has partnered with researchers from other universities across the country to demonstrate that swine shows and state fairs may be contributing to the spread of swine flu.

In a new study published today by the CDC’s journal Emerging Infectious Diseases, Bender and colleagues outline how almost 20 percent of seemingly healthy pigs at the 2009 Minnesota State Fair were carrying the influenza virus, and at least four were carrying the virus responsible for 2009’s swine flu pandemic.

“This study just shows that viruses are shared between pigs and people,” Bender told the Star Tribune, and that it may be harder to spot an infected pig than once thought.  “We were expecting, boy, if pigs had a virus then they should be [feverish], sick and easy to screen out.”  According to Bender that simply wasn’t the case.

For their part, Minnesota State Fair officials told WCCO-TV that animals will be closely monitored this year, especially in light of the more than 150 people sickened with a new type of swine flu – H3N2 – that has been linked to pigs at county or state fairs in Indiana and Ohio.  (It’s important to note that currently, no pigs in Minnesota have been found infected by the new strain of influenza.)

Minnesota State Fair officials will also be working to raise awareness around how people can limit the spread of illness and prevent the spread of swine flu.

According to Bender and his colleagues, people who work closely with pigs should receive seasonal influenza vaccines, use personal protective equipment when working with healthy pigs and limit their contact with sick pigs. Regular monitoring of influenza among pigs and testing of sick persons who have been exposed to pigs can also help minimize the spread.

For fair-goers, the message is also simple: if you go to the State Fair, wash your hands after being in the barn of any animals, don’t eat while in the barns and avoid contact with animals if you have a compromised immune system.

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