The US Centers for Disease Control and Prevention (CDC) are asking people attending agricultural fairs to take precautions when around pigs
because of a rise in the number of cases of a new strain of "swine flu" virus in humans. Especially vulnerable groups, such as the sick, the under 5s,
pregnant women and seniors should avoid contact with the animals altogether, they urge.
In a report issued on 3 August, the federal agency gave news of 12 new infections in humans with a strain of flu virus that normally circulates in pigs, bringing to 29 the total of lab-confirmed cases of human infection with the new variant of influenza A (H3N2) since July 2011.
10 of the new cases were reported from Ohio, 1 from Indiana, and 1 from Hawaii.
All 12 people had come into direct or indirect contact with swine before they fell ill, and with the exception of the one in Hawaii, the contact took place at agricultural fairs where sick pigs were reported to be present.
Most of the cases have been in children.
New Strain May Spread More EasilyDr Joseph Bresee, a medical epidemiologist in CDC's influenza division, said in a press briefing that:
"Twenty-nine cases of infection with this H3N2 virus since the fall of 2011 is a significant increase in the number of detections for these types of virus we've seen in recent years."
"While no human-to-human spread has been identified in recent cases, limited transmission from person to person is thought to have occurred on three occasions in the fall and winter of 2011," said Bresee.
All the 29 cases were infected with a strain of swine flu that contains the M gene from the 2009 H1N1 pandemic virus. The gene may make the new strain, called H3N2v, spread more easily to and among humans:
"This M gene may confirm increased transmissibility to and among humans compared with other variant influenza viruses," said Bresee.
The CDC say its own research suggests children under 10 don't have much immunity against the new variant, whereas adults may have some immunity from exposure to other flu viruses.
Symptoms and TransmissionWhile it is not common for swine flu viruses to infect humans, it can happen.
But only a lab test can tell if someone is infected with swine flu as opposed to human flu, because the signs and symptoms are the same, say the CDC.
Symptoms in pigs, as symptoms in humans, include: fever, depression (appearing listless and dull), sneezing, coughing (barking), runny discharge from eyes and nose, redness in the eyes, difficulty breathing, loss of appetite, and inflammation.
Swine flu viruses get into humans the same way as human flu viruses: via coughs and sneezes that propel the virus into the air which can then be breathed in by the next host.
Another way you can pick up the virus is if you touch a surface or object that has the virus on it, and then touching your mouth or nose.
There is no evidence you can get swine flu from eating pig meat and pork products that have been properly handled, say the CDC.
Vulnerable GroupsLate summer is a time of year when many Americans may come into contact with pigs, because it is high season for agricultural fairs and shows.
The federal agency emphasize they are not urging people to stay away from fairs, but to take precautions so as to make the experience is "a safe and healthy one".
However, they point out there are certain groups who are at high risk from serious complications if they become ill with flu. These are: children under 5, people aged 65 and over, pregnant women, and people who have asthma, diabetes, heart disease, weakened immune systems, and neurological or neurodevelopmental conditions:
"These people should consider avoiding exposure to pigs and swine barns this summer, especially if sick pigs have been identified," urge the CDC.
Take PrecautionsTo minimize the chance of catching flu from pigs, the CDC advises people take precautions when going near pigs, and especially if they touch them, handle them, or touch surfaces and items pigs are near or in contact with.
You should for instance, wash hands frequently, especially before and after touching or being near animals. And use soap and running water to make sure any contamination is thoroughly removed.
If you have animals, including swine, keep an eye out for signs of illness and call a veterinarian if you suspect they could be sick.
If at a fair, or if you keep animals yourself, never take food or drink into animal areas. And especially never eat, drink, or put things in your mouth when near animals.
The precautions are also important the other way around: if you have the flu or flu-like symptoms, stay away from animals.
If you must touch or go near pigs while you are sick, or if they are sick, then take extra protective steps. Wear gloves, protective clothing, masks that cover your mouth and nose, and other protective equipment.
The CDC say antiviral drugs oseltamivir (Tamiflu) and zanamivir (Relenza), which are used to treat infection with human seasonal flu, are also expected to be effective for the H3N2v virus.
And as with all flu, antivirals are most effective when started as soon as possible after illness begins.
More information on "good respiratory hygiene" can be found in the Compendium of Measures to Prevent Disease Associated with Animals in Public Settings, 2011 and What People Who Raise Pigs Need To Know About Influenza (Flu).
Written by Catharine Paddock PhD