At Least 12 Infected With New Swine Flu Strain

At least 12 people in five states have come down with a new strain of swine flu that isn't covered in this year's flu vaccine, the Centers for Disease Control and Prevention said.

The new strain is not the more common H1N1, that killed more than 17,000 people around the world over a two-year period. The new strain has been identified as H3N2v.

"In the second half of 2011, a number of U.S. residents were found to be infected with influenza A variant viruses, primarily H3N2v," the CDC said in a report. "Investigations revealed human infections with these viruses following contact with swine as well as limited human-to-human transmission."

Not known how widespread

While H3N2v viruses have been detected in U.S. swine, the CDC said it's unknown how widespread they are in swine herds. It's possible that sporadic infections and even localized outbreaks among people with this virus will continue to occur, according to the health agency.

So far, the CDC has counted only 12 cases. There are two in Indiana, three in Iowa, two in Maine, three in Pennsylvania and two in West Virginia.

"While there is no evidence that sustained human-to-human transmission is occurring, all influenza viruses have the capacity to change and it's possible that this virus may become widespread," the CDC warns.

Children appear more vulnerable

To date, the severity of illnesses associated with this virus in people has been similar to the severity of illnesses associated with seasonal flu virus infections. the limited studies that have been conducted so far suggest that adults may have some pre-existing immunity to this virus while children do not.

CDC said it is closely monitoring human infections with all novel influenza viruses, including H3N2v viruses, and will provide more information as it becomes available.

Swine influenza is a respiratory disease of pigs caused by type A influenza viruses that regularly cause outbreaks of influenza in pigs. Influenza viruses that commonly circulate in swine are called “swine influenza viruses” or “swine flu viruses.”

Swine flu viruses do not normally infect humans. However, sporadic human infections with swine influenza viruses have occurred.