An especially infectious form of swine flu swept across the globe in 2009. By year end, it had sickened an estimated 55 million people in the United States alone, killing more than 11,000. But pigs and people were far from the only victims of this virus, known as H1N1. Sea otters picked up the nasty bug, too, new data show.
What made scientists look for the germ in ocean animals? They recently found antibodies to the virus — signs of exposure — in northern elephant seals. Like the otters, they had been living off the coast of Washington State.
In their new study, government scientists analyzed blood from 70 sea otters. Some of those scientists work for the U.S. Geological Survey (USGS). Others study infections for the Centers for Disease Control and Prevention (CDC). Thirty of the blood samples were collected from healthy otters in 2011. Other samples came from cold storage. That otter blood had been collected long before the H1N1 global epidemic — or pandemic — emerged.
Seven out of every 10 otters that had blood drawn in 2011 had antibodies to swine flu. Antibodies are chemical residues in the blood. They show that the body’s immune system at some point fought against a particular foreign material or germ. Those antibodies can last for years. But no animals from before the 2009 flu pandemic had H1N1 antibodies.
Viruses can morph a bit from month to month and from year to year. The antibodies that an organism makes in response to a virus will show signs of which version of a germ its host has been exposed to. Antibodies in the otters had come from the version of H1N1 flu that was circulating in 2009, the new study shows.
Normally, new infectious human diseases develop first in animals. That’s why these are called zoonoses (ZOO oh NO seez) — from the Greek words for animals and disease. But sometimes the path of a disease goes in the other direction. Human infections can be passed along to animals.
“We are unsure how these animals became infected,” Zhunan Li says. Li is a microbiologist for the CDC in Atlanta, Ga. He led the group studying flu in otters. It’s not clear what role sickened people might have played in the animals’ infection, Li notes. After all, he points out, this otter species lives offshore “and rarely comes into contact with humans.” But if feces from people with flu got into the otters’ water, the animals certainly might have become exposed.
Otters also might have picked up the germ from elephant seals, Li’s team notes. The seals in which they found H1N1 antibodies spend part of their year in the same Washington waters where the otters live. But that raises the question: Where did elephant seals pick up the germ? One possibility: the feces of ducks. They are among a host of species (including chickens, whales, pigs and horses) in which flu has turned up before.
No one knows what an otter that is sick with flu looks like. By the time their blood was sampled, the Washington otters were healthy. But the new study “identifies sea otters as another marine mammal species that is susceptible to influenza viruses,” notes LeAnn White of USGS. A coauthor of the new study, she’s works at the National Wildlife Health Center in Madison, Wisc. The more animals that are vulnerable to flu, the more likely the disease can spread during epidemics.
That’s because such animals can serve as a reservoir for the disease, White notes. People who study infectious diseases refer to environments that can protect germs until they infect again as reservoirs. These can include bodies of water or feces shed by infected animals. Reservoirs also can include the tissues of living animals — even some with no symptoms.
Li’s team reports its findings in the May 2014 issue of Emerging Infectious Diseases.
antibody Any of a large number of proteins that the body produces as part of its immune response. Antibodies neutralize, tag or destroy viruses, bacteria and other foreign substances in the blood.
Centers for Disease Control and Prevention, or CDC An agency of the U.S. Department of Health and Human Services, CDC is charged with protecting public health and safety by working to control and prevent disease, injury and disabilities. It does this by investigating disease outbreaks, tracking exposures by Americans to infections and toxic chemicals, and regularly surveying diet and other habits among a representative cross-section of all Americans.
epidemic A widespread outbreak of an infectious disease that sickens many people in a community at the same time.
flu (short for influenza) A highly contagious viral infection of the respiratory passages causing fever and severe aching. It often occurs as an epidemic.
germ Any one-celled microorganism, such as a bacterium, fungal species or virus particle. Some germs cause disease. Others can promote the health of higher-order organisms, including birds and mammals. The health effects of most germs, however, remain unknown.
H1N1 A type of influenza virus that infects mainly swine. A few of the strains have developed the ability to spread in people as well.
immune system The collection of cells and their responses that help the body fight off infection.
infectious An adjective that describes a type of germ that can be transmitted to people, animals or other living things
microbiology The study of microorganisms, principally bacteria, fungi and viruses. Scientists who study microbes and the infections they can cause or ways that they can interact with their environment are known as microbiologists.
pandemic An epidemic that affects a large proportion of the population across a country or the world.
reservoir A large store of something. Lakes are reservoirs that hold water. People who study infections refer to the environment in which germs can survive safely (such as the bodies of birds or pigs) as living reservoirs.
residue A remnant or material that is left behind after something has been removed. For instance, residues of paint may remain behind after someone attempts to sand a piece of wood; or sticky residues of adhesive tape may remain on the skin after a bandage is removed; or residues of chemicals may remain in the blood after exposure to a pollutant.
sea otter A member of the weasel family, sea otters have the densest fur known among animals. That helps keep them warm in frigid waters, because these marine mammals don’t produce blubber — a thick layer of fat — as do seals and walruses.
virus Tiny infectious agents consisting of RNA or DNA surrounded by protein. Viruses can reproduce only by injecting their genetic material into the cells of living creatures. Although scientists frequently refer to viruses as live or dead, in fact no virus is truly alive. It doesn’t eat like animals do, or make its own food the way plants do. It must hijack the cellular machinery of a living cell in order to survive.
zoonosis (plural: zoonoses) Any disease that originates in nonhuman animals and is later contracted by people. Many zoonotic diseases also spread among a host of non-human species. For instance, the type of swine flu that sickened people throughout the world in 2009 also infected marine mammals, including sea otters.