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Flu is a contagious respiratory illness caused by influenza viruses that infect the nose, throat, and lungs. Those over 65, young children, and those with certain health conditions, such as asthma, heart disease, stroke, diabetes, and chronic kidney disease, have a higher risk of complications.

Flu season is generally during fall and winter months even though flu virus strains are detected every month. Over the past 40 years, the peak flu months were December through March, with February having more than double the cases of the other three months combined.

The overall health impact (infections, hospitalizations, and deaths) from the virus fluctuates from season to season. The Centers for Disease Control and Prevention (CDC) collects, compiles, and analyzes information on U.S. influenza activity year-round and produces a weekly report for medical providers and individuals to track trends.

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Between 3% and 11% of the U.S. population gets infected and develops flu symptoms each year.

Most experts say flu viruses spread mainly by tiny droplets when people with the virus cough, sneeze, or talk in close proximity to others. The virus might spread before you even develop flu symptoms. You are most contagious in the first three to four days after the illness manifests itself and remain contagious for up to five to seven days after becoming sick (although young children and those with weakened immune systems might remain contagious for longer).

Flu prevention begins with an annual flu vaccine. Vaccines have been shown to reduce flu-related illnesses and the risk of serious complications that can result in hospitalization or death. Medical providers do have access to “antiviral drugs,” which the CDC recommends for those with flu symptoms and especially for those at higher risk.

TRICARE covers the flu vaccine, which can be obtained three ways: through a military treatment facility (hospital or clinic), a network pharmacy, or a TRICARE-authorized provider (this might incur a copay for the office visit).