Is the Flu Airborne?

Some flu spreads through close contact, but there's some other transmission too.

Influenza, more commonly known as the flu, is most often spread when a person comes into contact with droplets or aerosols that contain mucus from an infected person.

Some research shows that approximately half of flu cases likely stem from airborne transmission. Knowing how the flu is spread and understanding flu transmission can help you prevent infection and minimize your risk. 

This article will discuss how flu is spread, including how long the flu is contagious and the flu incubation period. It will explain the difference between droplets and airborne spread, and how that might affect transmission. 

Cropped shot of a young man suffering with flu while sitting wrapped in a blanket on the sofa at home

Hiraman / Getty Images

Flu Transmission Explained 

The flu is a virus that is most often spread when someone comes into contact with droplets from an infected person. These droplets are produced when a person with the flu coughs or sneezes, spreading infected mucus around them for up to 6 feet.

Droplets vs. Aerosols

Droplets are heavy. They generally sink to the ground within about 6 feet of the infected person. That means if you stay more than 6 feet away, you are less likely to become infected. Scientists believe that most flu transmission happens when a person inhales these droplets or enters their eye, nose, or mouth. 

Aerosols are produced by coughing or sneezing, just like droplets. However, they are smaller and lighter, so they float in the air longer.

If the flu is airborne, that means the infectious virus can spread even if you stay more than six feet away. Researchers are still unclear about how much of the flu is spread via airborne transmission, but one study indicates that at least half of transmission happens via airborne particles.

Through Human Contact

When you’re close to someone, you’re more likely to come into contact with their respiratory secretions, such as mucus from the upper respiratory tract. The flu virus can also live on the skin of someone who has the virus, when these respiratory droplets or other bodily fluids fall to the skin. When you come into contact with these fluids, you can be exposed to the flu virus and contract influenza. 

On Surfaces 

Occasionally, the flu can be spread when you touch a surface that has the virus on it, then touch your own eyes, nose or mouth, allowing the virus to enter your body. This is called surface transmission. The flu can survive for up to 48 hours on hard objects like doorknobs. It survives for a shorter time on cloth and other porous surfaces. 

When You’re Contagious 

After you’ve come into contact with the virus, you can develop symptoms anywhere from one to four days later. You can begin spreading the flu one day before symptoms appear. You’re contagious for up to seven days, but most likely to infect someone else in the first three to four days of illness.

Staying Ahead of the Flu 

The best way to prevent the flu is by getting vaccinated with a flu vaccine and practicing good hygiene, including washing your hands frequently. To reduce your chances of contracting the flu:

  • Get vaccinated annually
  • Wash your hands frequently
  • Minimize contact with infected people, where possible
  • Stay home when you are sick
  • Avoid touching your nose, mouth or eyes, particularly in public
  • Lead an overall healthy lifestyle

Flu Season and COVID Prevention 

During the COVID-19 pandemic, there has been a dramatic decrease in flu cases, especially during the 2020-2021 flu season.

Researchers believe that this is largely due to COVID-related precautions including social distancing affected flu rates. Flu rates for the 2021-2022 season aren’t yet finalized but may be rising as COVID precautions lift. 

Summary

Influenza is primarily spread through airborne transmission via aerosols. These tiny particles are released when an infected person coughs, sneezes or talks and can float through the air for a long time. However, research indicates that some transmission of the flu happens from coming into contact with an infected surface. 

A Word From Verywell

Scientists are still studying how, precisely, the flu is spread. However, they know that certain precautions—including getting vaccinated and frequently washing your hands—can reduce the risk for flu transmission. Many of the same precautions that people have adopted to prevent the spread of COVID can also reduce your risk of spreading or contracting influenza.

Frequently Asked Questions

  • Is flu transmission similar to COVID?

    The flu and COVID are both viruses that are passed by coming into contact with respiratory secretions from an infected person. However, COVID appears to spread more easily than the flu, including through aerosols. In addition, people with COVID can be contagious for a longer time before they start exhibiting symptoms, which may contribute to the spread.

  • Does the CDC classify the flu as an airborne virus?

    The CDC maintains that most flu transmission happens from droplets, which stay within 6 feet of the infected person. However, research indicates that up to 50% of flu transmission happens via aerosols.

  • How contagious is the flu after you get a vaccine?

    Getting the seasonal flu vaccine reduces your risk of contracting the flu by 40%-60%, depending on the year. It also reduces your risk of hospitalization or death from the flu. All Americans who are 6 months or older unless advised otherwise by their healthcare provider can get the flu vaccine to reduce their risk of contracting the flu.

7 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Centers for Disease Control and Prevention. How flu spreads.

  2. Cowling BJ, Ip DKM, Fang VJ, et al. Aerosol transmission is an important mode of influenza A virus spread. Nat Commun. 2013;4:1935. doi:10.1038/ncomms2922

  3. Centers for Disease Control and Prevention. Cleaning to prevent the flu.

  4. Centers for Disease Control and Prevention. Healthy habits to prevent the flu.

  5. Harvard T.H. Chan School of Public Health. A sharp drop in flu cases during COVID-19 pandemic.

  6. Centers for Disease Control and Prevention. Similarities and differences between flu and COVID-19.

  7. Centers for Disease Control and Prevention. Vaccine effectiveness: how well do flu vaccines work?

By Kelly Burch
Kelly Burch is has written about health topics for more than a decade. Her writing has appeared in The Washington Post, The Chicago Tribune, and more.