The flu spreads through respiratory droplets, contaminated surfaces, and close contact, but a combination of simple habits can dramatically cut transmission risk. The most important thing to know: you’re contagious starting the day before symptoms appear and remain infectious for roughly five to seven days after. That means you can pass the virus to others before you even realize you’re sick.
How the Flu Spreads
Influenza travels between people through three main routes: large respiratory droplets (from coughing, sneezing, or talking), smaller airborne particles that linger in the air, and direct contact with contaminated surfaces or secretions. Large-droplet transmission is considered the predominant mode, which is why staying at least a few feet from a sick person matters so much. But because all three routes operate simultaneously in real life, no single precaution is enough on its own.
The virus survives on hard, nonporous surfaces like stainless steel, plastic, and countertops for 24 to 48 hours. On softer materials like cloth, paper, and tissues, it lasts less than 8 to 12 hours. That means a doorknob, light switch, or phone screen touched by someone with the flu can remain a source of infection for up to two days.
Stay Home Until You’re Truly Better
The CDC recommends staying home for at least 24 hours after both of these are true: your symptoms are improving overall, and you’ve had no fever without using fever-reducing medication. Leaving the house before that window closes puts coworkers, classmates, and anyone you encounter at risk during your most contagious days.
If you live with others, try to limit time in shared spaces while you’re symptomatic. Use a separate bathroom if possible. Sleep in a different room. These steps won’t eliminate transmission entirely, but they reduce the amount of virus household members are exposed to.
Hand Hygiene: Sanitizer May Edge Out Soap
Washing your hands is the single most repeated piece of flu-prevention advice, and it holds up. But the type of hand hygiene you use may matter more than you’d expect. A systematic review published in BMJ Open found that alcohol-based hand sanitizer was more effective than soap and water at reducing transmission of acute respiratory infections, and the difference wasn’t simply because people used sanitizer more often. The convenience factor does help, though: sanitizer takes less time, causes less skin irritation, and leads to more sustained compliance over the course of a day.
One trial in Swedish childcare centers found that adding an alcohol-based gel (70% ethanol) after regular handwashing reduced absenteeism by 12% compared to centers using soap and water alone. For practical purposes, keep a bottle of sanitizer with at least 60% alcohol near high-traffic spots in your home and workplace. Use soap and water when your hands are visibly dirty, since sanitizer doesn’t cut through grime as well.
Clean High-Touch Surfaces Often
Because the flu virus can stay infectious on hard surfaces for up to two days, regular disinfection of commonly touched objects is worth the effort. Focus on doorknobs, light switches, faucet handles, remote controls, phones, and shared keyboards.
Influenza is an enveloped (lipid-coated) virus, which makes it relatively easy to kill. Alcohol solutions at 60% to 80% concentration inactivate it effectively. Standard household disinfectants containing quaternary ammonium compounds also work against enveloped viruses like influenza. Diluted bleach (200 ppm available chlorine) can inactivate a wide range of viruses within 10 minutes of contact. The key with any disinfectant is contact time: the surface needs to stay wet with the product for the duration listed on the label, not just get a quick wipe.
Masks Reduce Risk Significantly
Face masks work against respiratory viruses, though the type of mask matters. A CDC study on indoor public settings found that consistently wearing an N95 or KN95 respirator was associated with an 83% reduction in the odds of testing positive for a respiratory virus compared to wearing nothing. Surgical masks offered a 66% reduction. Cloth masks showed a trend toward protection but the result wasn’t statistically significant.
If someone in your household has the flu, wearing a well-fitting surgical mask or N95 when you’re in the same room is one of the most effective things you can do. The sick person wearing a mask also helps by trapping droplets closer to the source.
Keep Indoor Humidity Above 40%
Dry indoor air is a friend to the flu virus. Research published in PLoS One found that aerosolized influenza retained 71% to 77% of its infectivity when relative humidity was at or below 23%, but only 15% to 22% when humidity reached 43% or higher. That’s a dramatic drop in viral survival just from adding moisture to the air.
During winter months, when heating systems dry out indoor air, running a humidifier to keep relative humidity above 40% can meaningfully reduce how long flu particles remain dangerous after a cough or sneeze. A simple hygrometer (available for a few dollars at most hardware stores) lets you monitor your home’s humidity level.
Vaccination Lowers the Odds
The flu vaccine won’t prevent every infection, but it substantially reduces your chances of getting sick and passing the virus along. Preliminary data from the 2024-2025 season shows vaccine effectiveness in outpatient settings ranging from about 42% to 56% for adults and 59% to 60% for children, depending on the surveillance network. For hospitalizations, effectiveness was higher, reaching 78% among children in one network and 55% among adults in another.
Even when the vaccine doesn’t completely prevent infection, vaccinated people tend to have milder illness and shorter periods of viral shedding, which means less time spreading the virus to others. Getting vaccinated protects not just you but the people around you, especially young children, older adults, and anyone with a weakened immune system who faces higher risks from flu complications.
Respiratory Etiquette Still Matters
Coughing or sneezing into your elbow rather than your hands keeps virus-laden droplets off the surfaces you touch throughout the day. If you use a tissue, throw it away immediately and clean your hands. These habits sound basic, but they interrupt the most common chain of transmission: droplets land on hands, hands touch a shared surface, and the next person touches their face.
Avoid touching your eyes, nose, and mouth when you’re around someone who’s sick or in crowded spaces during flu season. The mucous membranes in those areas are the virus’s entry point into your body. Keeping your hands away from your face, combined with regular hand hygiene, creates a meaningful barrier even when you can’t avoid being near someone who’s infectious.
Ventilation and Fresh Air
Because a portion of flu transmission happens through smaller airborne particles, improving airflow in indoor spaces dilutes the concentration of virus in the air. Opening windows, even briefly, introduces fresh air that pushes contaminated air out. If opening windows isn’t practical, portable air purifiers with HEPA filters can capture virus-carrying particles. In shared indoor spaces during peak flu season, any increase in ventilation helps reduce the risk for everyone in the room.