The last time swine flu swept through California and the country, in 2009, an estimated 59 million people caught it and 12,000 died. Half a million died globally.

And now, the pandemic influenza H1N1 virus is reportedly back in California, but this time, apparently, it is not quite the same threat to humans.

Researchers at the University of California, Davis have detected swine flu in elephant seals off the Central California coast, the first time a human pandemic strain has been found in marine mammals. Their research indicates it is the same flu that swept through human populations, but they don’t know precisely how it was transmitted to elephant seals.

There is some speculation that birds served as an intermediary out at sea.

The study was published this week in the online journal PLOS One. Scientists know that human flu virus can cross the barrier between species, but they reportedly have never observed a pandemic strain do it.

The scientists tested and tagged 72 uninfected elephant seals at two coastal locations in 2010. It was part of a larger project involving the tracking of 900 mammals among 10 different species. The seals were captured and retested after they returned from their annual spring foraging trip to Alaska.

Two of the seals were found to be infected and 28 showed antibodies indicating they had been exposed to the virus. None of the animals showed symptoms of illness, which can include a cough, a runny nose and fever. And none of them complained of other symptoms that can include muscle aches, a headache and fatigue.

Swine flu originated in pigs before making its way to humans in 2009. The disease is now considered under control and a seasonal affliction.

–Ken Broder    

To Learn More:

Swine Flu Turns up in Elephant Seals off Central Coast (by Jessica Shugart and Elizabeth Devitt, Contra Costa Times)

UC Davis Researchers Discover Swine Flu in California Elephant Seals (by Bill Lindelof, Sacramento Bee)

Pandemic H1N1 Influenza Isolated from Free-Ranging Northern Elephant Seals in 2010 off the Central California Coast (by Tracey Goldstein, Ignacio Mena, Simon J. Anthony, Rafael Medina, Patrick W. Robinson, Denise J. Greig, Daniel P. Costa, W. Ian Lipkin, Adolfo Garcia-Sastre and Walter M. Boyce, PLOS One)