Influenza is a viral infection that attacks your respiratory system — your nose, throat and lungs. Influenza is commonly called the flu, but it's not the same as stomach "flu" viruses that cause diarrhea and vomiting.
For most people, the flu resolves on its own. But sometimes, influenza and its complications can be deadly. People at higher risk of developing flu complications include:
Though the annual influenza vaccine isn't 100% effective, it's still your best defense against the flu.
At first, the flu may seem like a common cold with a runny nose, sneezing and sore throat. But colds usually develop slowly, whereas the flu tends to come on suddenly. And although a cold can be a bother, you usually feel much worse with the flu.
Common signs and symptoms of the flu include:
When to see a doctor
Most people who get the flu can treat themselves at home and often don't need to see a doctor.
If you have flu symptoms and are at risk of complications, see your doctor right away. Taking antiviral drugs may reduce the length of your illness and help prevent more-serious problems.
If you have emergency signs and symptoms of the flu, get medical care right away. For adults, emergency signs and symptoms can include:
Emergency signs and symptoms in children can include:
Your doctor will conduct a physical exam, look for signs and symptoms of influenza, and possibly order a test that detects influenza viruses.
During times when influenza is widespread, you may not need to be tested for influenza. Your doctor may diagnose you based on your signs and symptoms.
In some cases, your doctor may suggest that you be tested for influenza. He or she may use various tests to diagnose influenza. Polymerase chain reaction (PCR) testing is becoming more common in many hospitals and labs. This test may be done while you're in your doctor's office or in the hospital. PCR testing is more sensitive than other tests and may be able to identify the influenza strain.
It's possible to have a test to diagnose both influenza and COVID-19. You may have both COVID-19 and influenza at the same time.
Usually, you'll need nothing more than rest and plenty of fluids to treat the flu. But if you have a severe infection or are at higher risk of complications, your doctor may prescribe an antiviral drug to treat the flu. These drugs can include oseltamivir (Tamiflu), zanamivir (Relenza), peramivir (Rapivab) or baloxavir (Xofluza). These drugs may shorten your illness by a day or so and help prevent serious complications.
Oseltamivir is an oral medication. Zanamivir is inhaled through a device similar to an asthma inhaler and shouldn't be used by anyone with certain chronic respiratory problems, such as asthma and lung disease.
Antiviral medication side effects may include nausea and vomiting. These side effects may be lessened if the drug is taken with food.
Most circulating strains of influenza have become resistant to amantadine and rimantadine (Flumadine), which are older antiviral drugs that are no longer recommended.
Lifestyle and home remedies
If you do come down with the flu, these measures may help ease your symptoms:
To help control the spread of influenza in your community, stay home and keep sick children home until the fever has been gone for 24 hours. Avoid being around other people until you're feeling better, unless you're getting medical care. If you do need to leave your home and get medical care, wear a face mask. Wash your hands often.