What are flu antivirals?

What are flu antivirals?

Antiviral drugs are a type of prescription medicine used to treat viral infections. A flu antiviral works by stopping the flu virus from multiplying in your body, so it can no longer keep you sick.1

Antiviral medications for flu are not sold over-the-counter. Your doctor needs to prescribe them. They can help lessen flu symptoms, shorten the time you are sick, and help prevent flu from being spread to others.2,3

However, studies have shown that to make sure flu antivirals are as effective as possible, they must be prescribed within two days of you first noticing your symptoms.4 This is why it is so important that you speak to your doctor as soon as you think you might have flu.

Why it’s important to take flu antiviral medications within 48 hours of noticing symptoms
Why are antiviral flu medications important?

Flu is most contagious in the first 3 to 5 days, and even before symptoms occur you can still spread the virus to other people.5 Antivirals are designed specifically to shorten the length of the illness, avoid complications and minimize its spread to other people.2,3

For those at high risk of serious flu complications (for example people with asthma, the elderly and pregnant women,6 among others), antivirals can also reduce the risk of hospitalization and developing complications,7,8 and early treatment with an antiviral medication can reduce the risk of death in people who have been hospitalized.8

Find out more about how flu antivirals work

Think you’ve got flu? Visit your doctor to discuss if an antiviral flu medication might be right for you

If you get sick this flu season, it’s important to speak to your doctor or healthcare provider as soon as possible.


Find out more about flu in your local area using the CDC influenza map.


  1. Stiver G. CMAJ 2003; 168(1): 49–56.
  2. Tsang TK et al. Trends Microbiol 2016; 24(2): 123–133.
  3. Allen UD et al. Can J Infect Dis Med Microbiol 2006; 17(5): 273–284.
  4. Lehnert R et al. Dtsch Arztebl Int 2016; 113(47): 799–807.
  5. Centers for Disease Control and Prevention. Morbidity and Mortality Weekly Report, 2008; 57: RR-7. Available from https://www.cdc.gov/mmwr/pdf/rr/rr5707.pdf Last accessed September 2018.
  6. Mertz D et al. BMJ 2013; 347: f5061.
  7. Hayden FG & Pavia AT. J Infect Dis 2006; 194: S119–126.
  8. Centers for Disease Control and Prevention. Morbidity and Mortality Weekly Report, 2011; 60: 1. Available from https://www.cdc.gov/mmwr/pdf/rr/rr6001.pdf Last accessed September 2018.
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Date of preparation: November 2018

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