- For a healthy adult, the typical flu will last between one to two weeks.
- You should see a doctor if you’re experiencing symptoms out of the ordinary.
- People with compromised immune systems – either because of their age or health condition – are at a high risk for complications from the flu.
- This article was reviewed by Tania Elliott, MD, who specialises in infectious diseases related to allergies and immunology for internal medicine at NYU Langone Health.
- Visit Insider’s homepage for more stories.
Flu season in the US kicks off in October and lasts through May. While many healthy adults may be inconvenienced by the flu, everyone should know what to watch for – and when to head to the doctor if symptoms persist or worsen.
How long flu symptoms should last
For a healthy adult, the typical flu will last between one to two weeks. Following is a timeline of what symptoms you can expect and when, according to Julie Holland, a paediatrician with NorthShore University HealthSystem.
- Day 1: Symptoms come on abruptly, within an hour or two. You may have a fever, muscle aches, chills, cough, runny nose, headache, or all of the above. Many people are so fatigued that they have trouble getting out of bed. Children may feel nauseated and have diarrhoea or vomiting.
- Days 2-4: Remain home from work or school as the fever, chills, and body aches continue. You should stay home for a full day after your fever is gone because you can still spread the virus for five to seven days after symptoms start, according to the Centres for Disease Control and Prevention.
- Day 5: As your fever, chills, and body aches lift, you start feeling better. But you may still have flushed skin, watery eyes, and runny nose. Fatigue may continue for a few days to a week.
- Day 10: Most of your symptoms are gone, but the cough, runny nose, and fatigue can hang around for as long as two weeks.
When you should see a doctor
“People should see a doctor if they’re having symptoms out of the ordinary,” Holland says. “Cough or stuffy nose are normal. It’s not normal to have difficulty breathing.”
Emergency warning signs differ for children and adults, according to the CDC. No matter how long children have been sick, warning signs include:
- fast breathing or difficulty breathing
- bluish lips or skin tone
- chest pain
- severe muscle pain and difficulty walking
- fever above 104 degrees Fahrenheit
In adults, warning signs include:
- difficulty breathing or shortness of breath
- pain or pressure in the chest or abdomen
- extreme weakness
Who is most at risk with the flu
People at high risk for complications include adults over age 65, pregnant women, young children, and people with chronic diseases such as diabetes, cancer, or asthma. That’s because these people have compromised immune systems, either because of their age or health condition.
And while Holland estimates that only 10% of people who get the flu suffer complications, those complications can be life-threatening.
“Flu symptoms cause inflammation or fluid in your body,” Dr. Holland says. If the extra fluid and mucous doesn’t clear on its own in a few days, “that’s where the bacteria jump in and cause secondary problems.”
Bacteria – most commonly Streptococcus pneumonia, Staphylococcus aureus, and group A Streptococcus – can get trapped in swollen or fluid-filled areas, such as the sinuses, ear canals, or lungs. There, they breed, causing secondary infections that, if left untreated, could spread to other areas such as the heart or blood.
Complications from the flu range from common and easily treated to life-threatening, according to the CDC. Potential complications include:
Easily treated flu complications:
- sinus infection
- ear infection
- croup (common in children)
- bronchiolitis (common in children)
Potentially life-threatening flu complications:
- heart problems
- multi-organ failure
The flu also runs the risk of making underlying medical issues worse. For people with heart failure, diabetes, chronic obstructive pulmonary disease, or asthma, early intervention is key.
Don’t hesitate to check in with a physician. Inform them if you suspect you have the flu and mention that you’re at higher risk for complications. They may run a blood test to verify that you have the flu and not something else. They may also prescribe antiviral medications within the first 48 hours of developing symptoms to help minimise the severity and duration of the illness.
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