What is Flu?
Flu is a virus that causes flu attacks the respiratory system — the nose, throat and lungs. After the virus enters the body, it begins to multiply inside cells lining the airways. The immune system tries to fight off the infection, a defensive response that produces most flu symptoms.
Sometimes the flu can make people extremely sick. An out-of-control immune response can lead to significant tissue damage in the lungs. Also, an immune system overwhelmed by flu infection is vulnerable to secondary infection, usually by bacteria, which can trigger an extreme inflammatory response that damages multiple organs.
Causes of flu
The virus that causes flu spreads from person to person through tiny droplets that enter the air when an infected person sneezes or coughs. It is also possible to pick up the virus by touching an infected surface.
Learn About the Flu
Flu symptoms typically appear abruptly, whereas a cold usually comes on gradually. Symptoms can range from mild to severe, and may include:
- fever and chills lasting 3 or 4 days
- chest discomfort, cough
- muscle or body aches
- runny or stuffy nose
- sore throat
Flu can also cause serious or life-threatening complications, such as:
- ear and sinus infections
- encephalitis, inflammation of the brain
- kidney problems, such as acute kidney injury and hemolytic uremic syndrome
- myocarditis, an inflammation of the heart
- myositis and rhabdomyolysis, inflammation of muscle tissue
- pneumonia, a lung infection that can lead to sepsis or organ failure
The Centers for Disease Control and Prevention (CDC) recommends that everyone age 6 months and older receive a flu vaccine every year. Flu viruses are mutating all the time, so it is important to receive the latest vaccine. The best time to receive this year’s vaccine is by the end of October, the beginning of flu season. Some people experience flu shot side effects, but these are generally mild, such as redness or soreness at the injection site.
The flu vaccine is especially important for people at high risk of experiencing serious flu complications, including:
- adults aged 65 and older
- children younger than five
- healthcare professionals and caregivers
- pregnant women
- people in long-term care facilities such as nursing homes
- people with chronic disease or weakened immune systems
These tips for good hygiene can also help stop the flu virus from spreading:
- Avoid touching your eyes, nose and mouth
- Clean and disinfect frequently touched surfaces
- Cover coughs and sneezes with a tissue
- Wash hands often with soap and water or use hand sanitizer
Several tests are available to detect the flu virus. Rapid tests, such as rapid influenza diagnostic tests and rapid molecular assays, can provide results in as little as 10 minutes.
The most accurate flu tests require sending a sample, such as a swab of the nose or throat, to a laboratory for analysis. Results may take several hours. Options include:
- immunofluorescence assays
- reverse transcription polymerase chain reaction
- viral culture
Several prescription antiviral medications are available to treat influenza. The recommended drugs may vary from year to year to combat the specific flu virus that is circulating. Your healthcare provider will know which option is best for the current flu strain.