By Cheryl Pellerin
DoD News, Defense Media Activity
WASHINGTON, Oct. 27, 2014 - Flu season is underway and the Defense Department is making sure service members get flu shots because the illness, often considered mild, has a significant potential to affect operational readiness in unvaccinated units, an expert from the Defense Health Agency said this week.
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Air Force Lt. Col. Amy Costello, a pediatrician who specializes in public health, is chief of the Immunization Healthcare Operations Section in the Defense Health Agency Immunization Healthcare Branch. She spoke about flu vaccines at the Pentagon with DoD News.
"We always like to advocate for flu vaccine," Costello said. "It's that time of year and military treatment facilities all have most of their flu vaccine supply. So now, before flu season really kicks off, it's a great time to go get vaccinated."
Influenza, or flu, is a contagious disease that spreads nationwide every winter, usually between October and May, according to information posted on the Centers for Disease Control and Prevention website.
Anyone can get the flu
Flu is caused by flu viruses and spreads mainly by coughing, sneezing and close contact. Anyone can get flu, but the risk of getting flu is highest among children. Symptoms come on suddenly and may last several days. They can include fever or chills, sore throat, muscle aches, fatigue, cough, headache and runny or stuffy nose.
Flu can make some people much sicker than others, including young children, people 65 and older, pregnant women and people with health conditions, such as heart, lung or kidney disease, nervous system disorders, or a weakened immune system, the CDC said.
Flu vaccination is especially important for these people and anyone in close contact with them. Flu also can lead to pneumonia and can make existing medical conditions worse, the CDC said, and it can cause diarrhea and seizures in children.
Thousands of people in the United States die every year from flu and many more are hospitalized, according to CDC figures. Flu vaccine is the best way to protect against flu and its complications and it also helps prevent the virus from spreading.
Potential to impact operational readiness
"Flu is a bad disease," Costello said. "It killed millions of people during World War I and it has a significant potential to impact operational readiness in unvaccinated units. That's why the Department of Defense is so focused on getting everybody their flu shot every year."
In April 2009, an H1N1 swine flu began infecting people in Mexico and in June of that year was declared a global pandemic by the World Health Organization. According to the CDC, 60.8 million people were infected in the United States alone, nearly 275,000 were hospitalized and 12,469 died from this flu strain. Worldwide, the World Health Organization and others estimate that it killed 284,500 people.
In 2005, CDC researchers and their colleagues reconstructed the flu virus that caused the 1918-1919 World War I pandemic, which killed as many as 50 million people worldwide. It turns out that contagion was also an H1N1 swine flu virus.
Costello said there are different kinds of flu vaccine -- one is a nose spray that protects against four strains of flu, one is a shot with a vaccine that protects against three different strains of flu, and the other is a shot that protects against four different strains.
Multiple flu strains in a vaccine
The spray is recommended for people between ages 2 and 49, she said, "and there are some other restrictions - we don't give it to pregnant women and we don't give it to people who have asthma or people with egg allergies."
The spray is bad for people with egg allergies because standard methods used to produce flu vaccines rely on eggs to serve as a growth medium for the virus before it is harvested.
This method, developed more than 50 years ago and still in use today, first involves identifying which virus strains will go into a vaccine.
Virus strains are chosen for the vaccine each year depending on which ones are in common circulation. The 2014-2015 four-strain, or quadrivalent, vaccines include two influenza A strains, H1N1 and H3N2, and two influenza B strains.
Next, the strains are grown in millions of raw, fertilized chicken eggs before the viruses are harvested, purified and killed, then used in vaccines, according to a report on pandemic flu by the National Academy of Sciences.
Pandemics tend to be a problem
"The difference between [influenza] A and B is that they're two different genetic families of influenza," Costello said.
"Influenza A viruses tend to mutate faster, so every year it's a little bit of a scramble to keep up with what the virus is doing and to counter it," she said. "But influenza B viruses mutate more slowly and are more stable over time."
Pandemics tend to be a problem when virus strains mutate into a new strain of virus and people are less immune to them, she added.
About the pandemic 2009 H1N1 virus, the pediatrician said, "We've all gotten H1N1 shots for a few years now and we have some good immunity to it. If we suddenly had an [easily transmitted, highly pathogenic avian] H5N1 virus that came out next year, none of us would have immunity and it would have the potential to become pandemic, meaning that a lot of people get infected with it."
Because influenza B viruses mutates more slowly, she added, "We're less likely to be surprised by it. Our immune systems should recognize it and so it doesn't necessarily have the potential to catch the human race by surprise and cause a pandemic."
Ever-changing surface proteins
Another thing that makes influenza A viruses different is that they are divided into subtypes based on two proteins on the virus surface - hemagglutinin, or HA, and neuraminidase, or NA.
The subtypes are named according to their HA and NA surface proteins, which is what the letters H and N refer to in subtype names like H1N1, or H3N2, another swine-origin virus first detected in people in July 2011, according to the CDC. And these ever-changing surface proteins are targets for vaccines.
"Flu is dangerous," Costello said, "and the more people who are vaccinated the better. We think of flu as sort of a mild illness and we say it all the time - I had stomach flu or I had the flu - but unless you've had a fever for a week and haven't been able to get out of bed, it probably wasn't actually the flu."
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