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CDC: Increase seen in new swine flu strain

CDC: Increase seen in new swine flu strain
Friday, August 3, 2012 - 5:45pm

(CNN) -- Health officials have seen an uptick in cases of a new strain of swine flu in humans.

According to the latest flu report published Friday by the Centers for Disease Control and Prevention, 16 people have been infected with a new strain of an influenza A (H3N2) swine flu virus in just the past three weeks. Twelve of them were infected in the last full week of July.

Among those 12 newest cases, the CDC says 10 people were infected in Ohio; Indiana and Hawaii have reported one case each as well.

According to the CDC, so far a total of 29 people have been infected with this new H3N2 strain: 12 in 2011, one earlier in 2012 and 16 in the past three weeks.

Nobody was hospitalized this year, and only three of the 12 cases last year required hospitalization. Nobody has died from this new flu.

Everyone diagnosed with the new flu strain this year reported having contact with pigs. Most of the cases from last also reported contact with pigs -- often at county or state fairs.

"There are a few cases where no pig exposure could be found, so we think those are are human-to-human transmissions," said Dr. Joseph Bresee, an epidemiologist in the CDC's Influenza Division.

"We're not saying don't go to fairs," Bresee said, but because this is the time of year when many fairs are going on, people ought to take special precautions:

-- Wash your hands with soap and water before and after touching pigs.

-- Don't drink or eat near pigs, and don't take food into animal areas.

-- Avoiding contact with animals such as pigs may be the best protection if you are among those likely to suffer severe symptoms if you get the flu -- people with lung disease or diabetes, for instance.

H3N2 flu viruses are common among pigs. H3N3 viruses are a subgroup of influenza A viruses and they are known to adapt in humans, Bresee said.

What makes this new version of the H3N2 flu virus different is that it has picked up a gene from the novel H1N1 flu virus that became a pandemic three years ago. This can happen when a person or an animal is exposed to two different viruses at the same time.

Somewhere along the line, H3N2 and H1N1 viruses were present in a mammal at the same time and the "matrix-gene" (or m-gene) from the H1N1 pandemic virus was picked up by the H3N2 swine flu, thus creating a new or variant version of H3N2.

It is this m-gene that has experts on the lookout, because the presence of the m-gene can make it more easily transmissible to humans.

The majority of the children and adults who got the new strain were attending country or agricultural fairs, which is where they came in contact with pigs (the other pig-to-human transmissions occurred in farmers or veterinarians).

Health officials point out this flu is not a foodborne illness. Instead, it spreads like any other flu -- someone sneezes or coughs, spreading the virus to other mammals (humans included) and onto surfaces.

Dr. Lisa Ferguson, a veterinarian for the National Animal Health Policy Programs at the U.S. Department of Agriculture, said this variant of swine flu was first detected in 2010. Bresee said the first human cases were reported in July 2011.

Most of the people infected have been children; among the 16 cases this year, only three were adults, which is also consistent with what was seen last year, Bresee said.

CDC researchers said that while the genetic makeup of the flu strains found in all three states is similar, they do not believe the cases in Hawaii, Indiana and Ohio are related.

Even though the regular seasonal flu vaccine contains a strain of the A-flu virus group, it will not prevent you from getting sick if you come in contact with the new flu strain.

So Bresee said preliminary steps have been taken to develop an H3N2 vaccine -- part of the overall pandemic preparedness planning of the CDC and other health agencies.

When a new flu virus pops up, "we immediately begin to think about the process of making a vaccine," Bresee said.

The incremental process involves finding a good vaccine candidate, reassessing and testing the virus, developing seed vaccines and ensuring their safety. The goal is to have a vaccine quickly available in case a pandemic occurs, as with H1N1 in 2009.

Bresee said he is not equating this new H3N2 flu with the 2009 flu, but a new H3N2 vaccine and clinical trials are expected later this year.
 

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