The worst of flu season is upon us, and we're all holding our breath hoping we'll make it through the next few months unscathed.
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But if the usual symptoms – runny nose, cough, sore throat, breathing problems, fever, headache, diarrhea – hit this season, you'll probably just head to bed assuming it's a normal flu. However, the same symptoms could be the result of another lesser-known virus, one for which there's no readily available vaccine.
Unlike the common flu, adenoviruses can cause illness all throughout the year, not just during flu season. These viruses are similar to the flu, but are classified as a separate family. Although a vaccine is available, it's currently only available for military recruits.
"Most of the time, adenoviruses produce influenza-like illness with cough and runny nose and feeling crummy, but you get better," Dr. William Schaffner, an infectious disease specialist at Vanderbilt University, told CNN.
"But they can also cause conjunctivitis and, particularly in children, diarrhea," he added.
In some worse cases, individuals who contract an adenovirus may also develop pneumonia, an infection of the lungs.
"Of all the cases of pneumonia that occur in adults, about 5% are actually probably caused by adenovirus," Schaffner said.
And while the virus usually isn't severe, an outbreak killed 10 people in the United States back in 2007,
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Some experts also have warned that more serious cases have been cropped up, leading them to call for a vaccine to be made available to the general public.
"We are seeing severe adult infections," Dr. Adriana Kajon, the lead author of an Atlanta-based Centers for Disease Control and Prevention study on the virus published this week in "Emerging Infectious Disease", told NBC News. "That's a big deal, especially for a disease that by all means is vaccine preventable. But this vaccine is not licensed to be used in civilians."
John Su, who investigates infectious diseases for the CDC and contributed to a 2007 report on the virus, warned that adenoviruses can cause severe problems for individuals of any age.
"Whether you're a healthy young adult, an infant or an elderly person, this virus can cause severe respiratory disease at any age," he told Reuters.
The group of viruses can infect the nervous system, urinary tract, airways and lungs. Some strains can also cause an eye infection. It spreads primarily through close personal contact, meaning schools and crowded offices can be ready breeding ground for the illness.
And because severe cases are relatively rare, doctors do not normally test for the virus.
"Unless you look for it or you suspect it's circulating or you are using diagnostic testing capabilities that can tell it apart, you are going to miss it, especially during flu season," Kajon explained.
Adenoviruses are nothing new. They were first discovered in the 1950s and were named for the tissue behind the nose (adenoids) where they were first found in humans. Some 60 known types of the virus cause infections in people. Other strains can cause illness in various animals.
Experts also believe that although infections across the country appear small when data is compiled, many cases likely go unreported.
Schaffner explained that outbreaks are very sporadic. "Here a case, there a case," he said.
Those aiming to stay clear of the virus should take similar precautions as when trying to avoid the flu.
"Avoid people who are coughing and sneezing. Also avoid people who have pinkeye," Shaffner said.
But while researchers do think a readily available vaccine should be a priority, they also don't see cause for major alarm from the general public.
Shaffner said adenoviruses "cause principally a whole bunch of minor troublesome infections spread by children, often from children to adults."
"But they're not nearly as serious as influenza."
As long as you wash your hands regularly, avoid touching your eyes and stay away from others with symptoms, you'll probably be just fine.