The flu is so commonplace, but how many of us actually know what it is? Simply put, flu is a respiratory illness caused by influenza viruses. It can cause mild to severe illness that infects the nose, throat and occasionally, the lungs. In extreme cases, flu can lead to death. The best way to prevent catching this contagious illness is to get an annual flu vaccine. The CDC’s Advisory Committee on Immunization Practices encourages people over the age of 6 months old to get vaccinated.

How do you distinguish a flu from a cold?

Flu usually comes on suddenly. Symptoms typically occur one to four days after a person is exposed and infected. Even healthy people can be infected, but there are people at higher risk:

People 65 years and older and children younger than 5 years

Pregnant women

People with chronic medical conditions, such as asthma, diabetes and heart disease

If you smoke, the flu is yet another reason why you should quit. A study from the U.S. National Library of Medicine National Institutes of Health found that “influenza‐associated hazard ratio was greater in current and ex‐smokers than in never smokers for mortality of all-natural causes, cardiovascular and respiratory diseases.” The study also concluded that smoking may increase the risk of death in older people with influenza.

Flu viruses are spread via tiny droplets when infected people cough, sneeze or talk. The droplets can land in the mouth of nose of people in close proximity. Touching a surface that has been contaminated and then touching your mouth, nose or even your eyes is another way you can contract flu, although this happens less often.

Initially, the flu can present as the common cold. In addition to cold like symptoms you may feel some of the following symptoms: cough, sore throat, muscle/body aches, fatigue, runny/stuff nose, feeling feverish and chills. Vomiting and diarrhea are also symptoms but are more common in children than adults. Complications from flu can include ear and/or sinus infections, viral pneumonia, secondary bacterial pneumonia and worsening of chronic medical conditions.

In addition to getting vaccinated, the CDC recommends preventing the flu with frequent hand washing, staying away from people who are sick and covering coughs and sneezes. Strengthening your immune system by getting enough sleep, getting moderate exercise and eating a healthy, nutrient-rich diet also helps.

Much like COVID-19 protocols, sanitizing surfaces in your home is good practice if you or someone you live with comes down with flu. Disinfecting doorknobs, phones, light switches and other high-touch surfaces will reduce the risk of contracting the flu. Maintaining a safe distance and wearing a surgical mask and gloves if caring for a sick individual is also a smart choice.

If you have the flu, you are most contagious three to four days after your illness begins. You may be able to spread flu to someone else before you know you are sick, as well as while you are sick. Some otherwise healthy adults may be able to infect others beginning one day before symptoms develop and up to five to seven days after becoming sick. Certain people, like young children and people with weakened immune systems, might be able to infect others for an even longer time.