9/27/2026 – Written by the Hand Hygiene team. This article replaces our 2009 piece on preventing swine flu.
How respiratory viruses spread
Flu, COVID-19 and RSV spread mainly through the air, in droplets and smaller particles people release when they breathe, talk, cough or sneeze. They can also spread when someone touches a contaminated hand or surface and then touches their eyes, nose or mouth. That second route is where hand hygiene matters.
Where hand hygiene fits
In 2024, CDC combined its guidance for COVID-19, flu and RSV into one set of recommendations. Hygiene, meaning washing your hands regularly and cleaning commonly touched surfaces, is one of four core prevention strategies. The other three are staying up to date on recommended vaccines, taking steps for cleaner indoor air, and taking precautions when you are sick: staying home, keeping away from others, and getting treatment early if you are at higher risk.
No single step does all the work. Clean hands will not stop a virus you breathe in, but they cut one of the easiest routes into your body.
When to clean your hands
- After coughing, sneezing or blowing your nose
- Before eating, and before touching your eyes, nose or mouth
- Before and after caring for someone who is sick
- After touching shared surfaces in public, such as door handles, railings and shopping carts
- When you get home
Cover coughs and sneezes with a tissue or your elbow. If you use a tissue, throw it away and clean your hands right after.
Soap or hand sanitizer?
Both work against these viruses. Flu viruses, coronaviruses and RSV have a fragile outer envelope that soap breaks apart and alcohol destroys. Wash with soap and water for at least 20 seconds when you can (see our handwashing steps). When you cannot, use a hand sanitizer with at least 60% alcohol and rub until your hands are dry. Use soap and water when your hands are visibly dirty.
Looking back
When H1N1 "swine flu" spread in 2009, handwashing was one of the main messages from CDC and WHO, as it was again at the start of the COVID-19 pandemic in 2020. COVID-19 also showed the limits of hand hygiene alone: the virus spreads mostly through the air, so vaccines, ventilation and staying home when sick carry much of the load. Hand hygiene remains the easiest step anyone can take every day.
Sources
- CDC. Preventing Respiratory Illnesses. Reviewed August 2025.
- CDC. CDC updates and simplifies respiratory virus recommendations. March 1, 2024.
- CDC. About Handwashing (Clean Hands).