Influenza, the dreaded cold-weather virus, was once believed be brought on by the influence of the stars. Although that particular flu myth has been dispelled, doctors still battle others about the flu and its vaccine each season.
"Flu myth busting is the most difficult thing I do," said Dr. Len Horovitz, pulmonary specialist at Lenox Hill Hospital in New York City.
From how you get the flu to how you fight it off to concerns over the safety of the seasonal flu vaccine, there's a lot of misinformation out there that may leave people underprotected for flu season, doctors say.
ABC News asked experts to set the record straight on 15 hard-to-shake flu myths.
Despite the continual urging by the Centers for Disease Control and Prevention that all Americans over the age of 6 months should be vaccinated against the seasonal flu, only 30 to 55 percent of eligible people in the U.S. got vaccinated in 2010, according to CDC data. Much of this lag in vaccination rates stems from lingering fears over the safety of the vaccine.
This fear began in 1979, when live-virus vaccines were used and people did get sick from them, says Horovitz. "That was the start of people deciding they weren't going to get a flu shot," he says.
But today, injectable flu vaccine uses dead virus and "is made up of only parts of the flu virus, so it cannot in any way give you the flu," says Dr. William Schaffner, chairman of Preventive Medicine at Vanderbilt University Medical Center. While the nasal spray variety of the vaccine uses a live, weakened virus, it can only multiply in the colder environment of the nose and can't give you the actual, full-blown flu. Sometimes people have a sore throat and runny nose for a day, but not the actual flu, Schaffner says.
One reason that this myth persists is that flu vaccine causes a brief fever in about 1 percent of recipients, which leads some to worry that they are actually getting the flu after getting the vaccine. "These are very transient and rare reactions," Schaffner says, and do not indicate that the patient has the flu.
Another issue is that it can take several weeks for the vaccine to cause the buildup of enough antibodies in the body to become effective, "so it is quite possible to get the flu soon after getting vaccinated, which could lead to this misunderstanding," says John Barry, author of "The Great Influenza."
The flu vaccine is given in the hundreds of millions of doses every year and is "extraordinarily safe," Schaffner says. Other doctors echo this sentiment -- that the flu itself is the threat, not the vaccine.
There are very rare risks associated with any vaccine, notes Dr. Christian Sandrock, a physician and an expert in infectious disease at the University of California Davis Medical Center, but it's about weighing the benefits of vaccine against the risk.
"What is far more dangerous is taking the risk that you will get infected with flu if not vaccinated," says David Topham, co-director of the New York Influenza Center of Excellence. "Flu infection kills almost 40,000 people each year in the U.S. alone. Flu vaccine does not kill anyone."
Fears about the use of the flu vaccine by pregnant women stem from generations past, when women were advised against getting any vaccine while pregnant, says Dr. Greg Poland, director of the Vaccine Research Group at the Mayo Clinic in Rochester, Minn.
"This was because the vaccines a generation ago were live virus vaccines. Today, the injectable vaccine is just pieces of protein and there is no risk of getting the flu from it," he says. The nasal vaccine, which does contain live virus, however, is not recommended for pregnant women.
Getting the flu, and the high fever that accompanies it, is much more of a concern for pregnant women, Poland says, because high fever in the early stages of pregnancy can lead to certain neurologic brain defects in the baby. Hence, preventing flu infection with vaccination and getting early treatment is of the utmost importance for pregnant women.
Considering that those who are young and healthy generally fend off flu better than younger children, senior citizens and those with compromised immune systems, many believe that it's not that important for those at low risk of suffering flu complications to get vaccinated. But this couldn't be farther from the truth, says Schaffner.
"The flu is a viral disease that can put you in bed and into the hospital very quickly, even in young, healthy people. Even if the flu only does this to one out of every 300 young healthy people, we can't pick those people out in advance, so we want to protect everyone," he says.
More importantly, widespread vaccination is critical to protect, not just you, but the people around you.
"Vaccines have two functions: they protect the person who is vaccinated, but also everyone around that person -- because the person will not spread the flu," Schaffner says. "And someone around that young, healthy person may have diabetes, or be elderly, or be a small infant, and you want to protect these people from getting sick."
Verdict: Not Quite
The flu vaccine is only about 59 percent effective at warding off flu, according to a review published in the October issue of The Lancet Infectious Diseases. Nevertheless, experts say the flu shot is still the best defense against the virus.
"While we hope and wait for a perfect vaccine, we've got a good one that's capable of preventing influenza and its complication," said Schaffner. "It can't prevent every instance, but it can prevent many. And that's a good thing."
Because the vaccine has its limitations, other methods of flu prevention such as hand washing and staying away from those who are sick are still very important. Regular exercise, getting plenty of sleep, and cleaning commonly-used surfaces at home frequently are also good ways to stop the flu in its tracks.
Verdict: Not Quite
Often, there is a misconception that there is just one influenza strain that circulates in any given season. If this were the case, then getting the flu once would provide your body with the antibodies necessary to fight off that flu and prevent you from coming down with the flu again that season.
"If only this were the case," says Schaffner. Instead, there are hundreds of different types of flu viruses that circulate at any given time, so if you get the flu once, you only have protection from that specific type of flu.
In terms of vaccination, this means that just because you got the flu already, this doesn't meant that you should still get the vaccine. You are still susceptible to other types of flu and the vaccine offers the best, although not full-proof, protection against getting these other strains, Schaffner says.
Verdict: Definitely Not True
As stated above, there are hundreds of different strains of flu virus, and these strains change constantly. Every year, the vaccine is made by selecting the three most common types of virus that are currently circulating.
"That's why we need a new vaccine every year," said Schaffner.
For the same reason that getting the flu in November won't protect you from getting another strain in December, getting the vaccine for the strains of flu circulating in 2010 will not necessarily protect you from the types that will be circulating in 2011.
Scientists are working toward a stronger, more universal vaccine that could be a one-shot deal -- with the occasional booster.
While it's better to get the vaccination before the flu season peaks, that doesn't mean it's too late to protect yourself by vaccinating in January or February or even March.
"Flu peaks in February and early March, so there's still time to get vaccinated," says Schaffner, "but that's why I say jog, don't walk, to the drug store to get vaccinated today."
Verdict: Mostly False
Getting severely chilled to the point of hypothermia can make the immune system less resilient, which may make someone more susceptible to flu, doctors say, but you still have to come into contact with the flu to get the flu – and getting a chill, in and of itself, is not going to do it.
Also, your standard amount of "chill" from a drafty window or going out with wet hair is not going to be enough to predispose you to illness, Schaffner says.
Verdict: The Data Suggest Not
Despite speculation that taking large doses of vitamin C or echnicacea will protect people from flu, the data just aren't there to support them as flu-fighters, Schaffner says. There's some mixed evidence that these supplements will help fight off a cold, but when it comes to flu, these methods "strike out," he says.
Verdict: No, Antiviral Medication Will
While antibiotics are sometimes used to control infection such as pneumonia that can accompany serious bouts of flu, antibiotics cannot treat viral infections like the flu.
Antiviral mediation such as Tamiflu and Relenza can fight off the flu virus, but even these can only shorten the duration of the illness, not resolve it altogether, Horovitz says.
Verdict: Please Don't This old adage may sound nice, but there is "no science to prove that it works," says Dr. Peter Katona, an infectious disease specialist at UCLA Medical Center. "You don't starve a flu, you need food and liquids for both [flu and cold]."
"Keeping up fluids is most important," Schaffner adds, "and if you're hungry, keep it to simple foods to go easy on your tummy. This is not the time to get spicy Szechuan chicken."
Verdict: Not Necessarily
For most people who get the flu, staying at home and getting rest and plenty of fluids will be enough for their bodies to fight it off. If your fever doesn't go away or your symptoms become severe, seek medical attention, says Schaffner. It doesn't matter how young and healthy you were a few days ago. Flu complications can become serious and antiviral medications or hospitalization may be needed.
Seeking immediate medical attention is especially important if you develop a headache and severe stiffness in your neck as this may be a sign of bacterial meningitis, not the flu.
Bacterial meningitis starts out with flu-like symptoms such as fever and achiness, but quickly the patient will become seriously ill, will be so stiff as to be unable to put his/her chin to the chest, and will be difficult to rouse from sleep, Schaffner says.
Bacterial meningitis can lead to brain damage, coma, and death when left untreated so any of these symptoms should not be ignored.