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Sea Otters Can Get Your Flu
Sea Otter Dining on Crab

A sea otter dines on crabmeat in Monterey Bay, California. USGS scientists study sea otters to help the threatened species continue to recover from near extinction.

Social, fun-seeking, comedic, and sometimes feisty, sea otters are endearing because they’re a lot like us. Scientists now know that we have something else in common with sea otters: Both of us can get the flu.

During an August 2011 sea otter health monitoring project, scientists with the U.S. Geological Survey and Centers for Disease Control and Prevention found that northern sea otters living off the coast of Washington state were exposed to the same flu virus that caused the 2009 world-wide pandemic in people. The exact date and source of exposure could not be determined, but the findings suggest that human flu can infect sea otters.

“Our study shows sea otters to be a newly identified animal host of influenza viruses,” said USGS scientist Hon Ip.


Kelp Forest

Sea otters are critical for the health of kelp forests.




Compromised Cuties

Otters are valuable beyond their child-like charisma:

  • Sea otters are considered a keystone species of the kelp ecosystem because they prey on plant-eating organisms that, if left unchecked, can destroy kelp beds and the fish habitat they provide.
  • Scientists study sea otters as an indicator of nearshore ecosystem health, since sea otters feed and live near the coast and often are the first predators exposed to pollutants and pathogens washed down from coastlands.

However, sea otters are also imperiled. These marine mammals were nearly killed off due to intensive fur harvesting in the 18th and 19th centuries. Today, two wild sea otter populations in the U.S. are federally listed as threatened, which makes otter diseases — including flu — all the more dire.

The 2009 Pandemic

If you or someone you know got sick from the 2009 H1N1 influenza virus, commonly called “swine flu,” you weren’t alone. That year, the World Health Organization declared the infection a pandemic. The CDC estimates that between 43 million and 89 million human cases of the H1N1 infection occurred in the United States between April 2009 and April 2010, causing up to 18,300 related deaths.

Sea Otter Hunt at Sunrise

USGS marine biologists set sail on a crisp September morning to capture and tag wild sea otters to monitor the health of this threatened species.

The H1N1 virus has spread globally among people since 2009 and was the predominant flu virus in circulation during the 2013-2014 flu season.


The Otter Victims

The USGS and CDC researchers discovered antibodies for the 2009 H1N1 flu virus in blood samples from 70 percent of the sea otters studied during a 2011 otter health monitoring project. None of the otters were visibly sick, but the presence of antibodies means that they were previously exposed to influenza.

Further tests concluded that the antibodies were specific to the pandemic 2009 H1N1 flu virus, and not from exposure to other human or avian H1N1 viruses.

So, how did these animals get sick?

Scientists aren’t sure.

“This population of sea otters lives in a relatively remote environment and rarely comes into contact with humans,” said CDC scientist Zhunan Li.

An unrelated 2010 study showed that northern elephant seals sampled off the central California coast had also been infected with the 2009 pandemic H1N1 virus. This elephant seal exposure is the only other known pandemic H1N1 influenza infection in marine mammals, and similar to sea otters, it is unclear how the seals were exposed.

The new study is the first time that evidence of influenza infection has been detected in sea otters, although these viruses have previously been found in many other animals, including ducks, chickens,  pigs, whales, and the seals.

“Our report identifies sea otters as another marine mammal species that is susceptible to influenza viruses and highlights the complex interspecies transmission of flu viruses in the marine environment,” said USGS scientist LeAnn White.

USGS Research

  • Sea otter flu and wildlife diseases: TheUSGS National Wildlife Health Center and the Department of the Interior work with CDC and other partners on research related to zoonotic diseases — diseases that can be passed between animals and humans — to help provide an early warning to the agriculture, public health and wildlife communities, and to the public. Sea otter sampling for the USGS/CDC study was performed by a collaboration of USGS science centers, the Monterey Bay Aquarium, and the Seattle Aquarium.
  • Sea otters in general: Scientists from the USGS Alaska Science Center and USGS Western Ecological Research Center study sea otters and the ecosystems in which they live to help the threatened species continue to recover from near extinction. They work with state, federal, and local partners throughout the species’ range, using tools and expertise from ecology, chemistry, geography, and other disciplines.

More Information

California Sea Otter Stranding Network:

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Page Last Modified: November 7, 2013