A 33-year-old pregnant woman from China has become the latest victim of the H7N9 virus, the same bird-transmitted infection that caused worldwide alarm when it first emerged in 2013.

Officials say as of Tuesday there have been 51 confirmed cases of H7N9 in the Guangdong province on the South China Sea coast, according to the Chinese news service Xinhua.

The virus kills one third of those infected and it has been a tough one to fight.

Initially, scientists believed seasonal flu vaccines couldn’t protect humans against H7N9, but new research released this week says otherwise.

Flu Vaccine Activates Bird Flu Antibodies

Researchers at the University of Chicago and the Icahn School of Medicine at Mount Sinai in New York came across an unexpected result when they were studying flu shot reactions.

In their study, published Tuesday in The Journal of Clinical Investigation, the research team reports the flu vaccine activates three of the 83 antibodies that attack H3 viruses, including H7N9.

“It appears more common than previously thought for antibodies induced by flu vaccination to offer cross-protection against H7N9,” Carole Henry, study author and a postdoctoral fellow at the University of Chicago, said in a statement. "Although they are not always protective, H7-reactive antibodies can be found in almost everyone that's been vaccinated."

Researchers discovered the antibodies by taking samples from 28 vaccinated people and isolating 83 antibodies that react with H3N2, a strain of the common flu virus. While no H7 strains were part of the vaccines, 7 percent of the antibodies “appeared to completely neutralize H7N9 avian flu.”

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To verify their findings, researchers treated selected lab mice with each antibody while other mice did not receive the protection. All the mice were given lethal doses of the H7N9 viruses. The mice that received the antibodies survived while the others did not.

Besides H7N9, researchers discovered the flu vaccine can protect against other H3 and H7 strains. Even if the antibodies weren’t able to prevent the viruses from mutating, they were successful in making them less infectious.

The flu vaccine is designed to protect against three common flu viruses: H1N1, H3N2 (both influenza As), and influenza B.

While it may be some time before a vaccine against H7N9 and other lethal viruses is readily available to the public, the Mt. Sinai-Chicago team hopes to expand their research into more effective flu vaccines.

“The challenge is to exploit this response on a larger scale to make vaccines or therapeutics that offer broad protection against influenza strains,” Patrick Wilson, co-senior author and an associate professor of medicine at the University of Chicago, said. “For now, it's clear that seasonal flu vaccination provides defense against more than just common strains. Everyone should be vaccinated.”

A Changing Vaccine for an Evolving Virus

Every year new flu vaccines are formulated in an attempt to battle the ever-changing flu virus.

The Centers for Disease Control and Prevention (CDC) reports the flu vaccinations given this year don’t adequately cover viruses circulating in public. The flu shot has reduced the risk of having to go to the doctor by only 23 percent.

Flu vaccinations work by introducing small amounts of a dead virus into a person’s body, allowing the body’s immune system to develop antibodies to fight live versions of the virus.

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The CDC recommends everyone 6 months or older receive an annual flu shot, including pregnant women and people with chronic health conditions.

People who shouldn’t get the vaccine are those with severe allergies to the vaccine or its ingredients, including gelatin or antibiotics.

Why It’s Called ‘Avian Flu’

H7N9 was dubbed “avian flu” because it is transmitted by poultry. While experts aren’t exactly sure why some forms of the virus are able to transfer from animals to humans, H7N9 has quickly spread through densely populated parts of China with open poultry markets.

The disease rarely shows traditional flu-like symptoms, but instead develops into severe cases of pneumonia, according to the World Health Organization.

Prior to March 2013, there were no known cases of H7N9 in humans, but the virus’ debut season resulted in 132 infections in people along with 44 deaths, according to the CDC.

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