What Happens When You Get the Flu — and What to Do at Every Stage

When the flu comes at you, brace yourself for a tough time.

“It’s like a truck hit you,” says Carlene Muto, MD, an infectious disease specialist and medical director of infection prevention at Temple Health in Philadelphia. (The common cold, in contrast, tends to come on more gradually.) “You have muscle aches, headache, and you’re so tired you can’t get out of bed.”

As you lie there, you may wonder when you’ll start to feel better and what to expect as the virus runs its course. This day-to-day guide will help you understand the different stages of the flu and when relief may be in sight.

A caveat: Anyone at any age can get the flu, but the impact will vary from person to person. For those with weakened immune systems, such as older adults, it can take longer than average to recuperate, and complications (some of them potentially life-threatening) are more likely.

When the influenza virus first enters your body, you’re likely to feel fine and not realize that a storm of sickness is about to break.

“During incubation, the virus replicates in the respiratory tract before symptoms begin,” says Diego R. Hijano, MD, an associate member in the department of infectious diseases at St. Jude Children’s Research Hospital in Memphis, Tennessee. “It takes time for the virus to multiply and for the immune response — which causes most symptoms — to activate and start fighting off the virus.”

When Do You Become Contagious With the Flu?

• Sudden onset of fever (sweating and chills)
• Muscle and joint pain
• Headache
• Severe malaise (feeling unwell)
• Fatigue
• Cough (usually dry)
• Sore throat
• Runny nose

Fever, chills, and body aches are earlier symptoms that appear in the first one to three days. Cough, sore throat, and runny nose (symptoms the flu shares with the common cold) tend to appear later, says Geeta Sood, MD, assistant professor of medicine at the Johns Hopkins University School of Medicine and hospital epidemiologist at Johns Hopkins Bayview Medical Center in Baltimore.

“One thing I wanted to point out is that most people think you have to have a fever to have the flu,” says Muto. “Although fever is a good sign that you have the flu, not everybody who has the flu has a fever.”

You can transmit the virus to others during this period, so staying home is important both to aid your recovery and to avoid making other people sick.

Home Remedies and Over-the-Counter Treatments

• Drink lots of liquids. Water, juice, warm soups, and other fluids can help your body prevent dehydration that can occur because of increased sweating. Muto recommends drinks with electrolytes, such as Gatorade and Pedialyte, as they aid in the retention of fluids. “For children, keeping them hydrated is especially important, since young kids can get dehydrated quickly when they’re sick,” says Dr. Hijano.
• Get plenty of rest. Sleep and reduced exertion help the immune system fight the infection.
• Take pain relievers. Acetaminophen (Tylenol) or ibuprofen (Advil, Motrin IB) can reduce fever, headache, and aches. Children and teens recovering from flu-like symptoms should never take aspirin because of the risk of Reye’s syndrome, a rare but potentially fatal condition.
• Lozenges can help ease sore throats, and over-the-counter decongestants, such as pseudoephedrine (Sudafed, Claritin-D, Mucinex D), can also provide relief for nasal symptoms.
• Muto notes that some supplements — such as zinc and elderberry — have been shown to boost the immune system, although studies have not confirmed their effectiveness in fighting flu.

Antivirals for Those at High Risk

People who are at high risk of severe flu complications may want to consult a doctor early on in the course of the illness to start any prescription treatments, says Sood. These groups include young children, pregnant women, older adults, and those with chronic conditions, such as high blood pressure or diabetes.

There are four main antiviral medications available to people who are more likely to have severe complications from the flu. All work best when taken within 48 hours of symptom onset.

“Oseltamivir [Tamiflu] is the most commonly prescribed,” says Hijano. “Zanamivir [an inhaled medication] and peramivir [an intravenous option] are reserved for specific situations, such as when oral therapy isn’t possible. Xofluza [baloxavir marboxil] is a newer, single-dose antiviral approved for individuals 12 years and older.”

• Your symptoms are getting better overall.
• You have not had a fever and are not using fever-reducing medication.

Even after you’ve recovered from the flu, “fatigue or cough may linger for up to two weeks,” says Hijano.

Muto urges patients to continue to get enough rest, eat healthy, and gradually phase in more exertion until their energy is back.

• Chest pain
• Difficulty breathing or shortness of breath
• Ongoing dizziness
• Seizures
• Worsening of existing medical conditions
• Severe weakness or muscle pain

Additional emergency symptoms to look for in children include:

• Gray or blue lips or nail beds
• Fast breathing or ribs that pull in with each breath
• No tears when crying and a dry mouth, along with not needing to urinate
• Symptoms, such as fever or cough, that get better but then come back or get worse

“For infants, it can be harder to recognize symptoms of pain or distress, so parents should watch for signs like inconsolable crying, difficulty feeding, or unusual sleepiness,” says Hijano.

• Most cases of flu get better in about a week.
• Some people are more susceptible to serious complications and may want to take antiviral medications. Tamiflu is most effective within the first 48 hours of symptom onset.
• Vaccination is considered the best way to protect yourself from severe illness.