How effective is handwashing at preventing flu transmission?

Influenza, known more commonly as the flu, is a contagious illness that affects the respiratory (breathing) system. The most common symptoms include fever, sore throat, runny nose, general aches and pains, cough, and fatigue. It can range from a mild illness that goes away on its own with rest and fluids to a severe illness requiring hospitalization. In certain cases, it can lead to death. 

There are two main types of influenza viruses (type A and type B). Death is an extreme outcome of flu, but there are other, more common outcomes that have an important impact every year. These include missed days of work, school, and increased burden on the healthcare system.

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According to the CDC, the single best way to prevent flu is to get a flu vaccine every year. Good hygiene, such as washing hands and covering a cough or sneeze, can also help prevent viruses like influenza from spreading. It's hard to tell exactly how much handwashing prevents flu transmission in the community. However, because of its proven effectiveness in other settings, handwashing remains an important strong recommendation in preventing the spread of the flu (Moncion, 2019).

In a study of over 1,200 people, hand hygiene helped reduce influenza transmission among household contacts when practiced within 36 hours of the person showing symptoms (Cowling, 2009).

The best practices for washing hands are (CDC, 2020):

• Wet your hands with clean, running water (warm or cold), turn off the tap, and apply soap

• Scrub your hands for at least 20 seconds and make sure to get the backs of your hands and the spaces between your fingers.

• Rinse hands well under clean, running water

You may also consider using a paper towel to open the door afterward.

In the United States, flu season (the time when most people get the flu) is in the fall and winter (CDC, 2020a). The number of people affected is different each year, depending on infection control practices, how many people get the flu vaccine, how effective that year’s flu vaccine is, and other factors. In the 2019–2020 flu season, the CDC estimates that 38 million people in the US had the flu and that 18 million (about half—47%) of them had to see a doctor for the flu (CDC, 2020b).

While overall mortality rate (the percentage of people who had the disease that died from it) is a rough indicator of how deadly the flu is, it is important to remember that the risk of severe illness depends on many factors, like age and how sick the person is at baseline (i.e. if they have any chronic illnesses).

In the 2019–2020 flu season, an estimated 22,000 people died from the flu or complications (of the 38 million who had the flu).

The CDC says that washing hands with soap and water as above is the best way to reduce the spread of infection in most situations, but an alcohol-based sanitizer with at least 60% alcohol can also be used as long as hands are not visibly dirty or greasy (in which case you should wash with soap and water).

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Current version

November 03, 2021

Written by

Rachel Kwon, MD

Fact checked by

Yael Cooperman, MD

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About the medical reviewer

Yael Cooperman, MD, Ro

Yael Cooperman is a physician and works as a Senior Manager, Medical Content & Education at Ro.