Hepatitis A spreads through the fecal-oral route, meaning you get infected by swallowing something contaminated with the virus from an infected person’s stool. That can happen through contaminated food, contaminated water, or direct contact with someone who has the infection. The virus travels to your liver, multiplies there, and then gets released back into your intestines and shed in your stool, continuing the cycle of transmission.
Contaminated Food
Food is one of the most common vehicles for hepatitis A, and contamination can happen at any point from the field to your plate. The single biggest source of foodborne outbreaks is an infected food handler at a restaurant, catering event, or other point of sale. Because the virus sheds in stool, a food worker who doesn’t wash their hands thoroughly after using the bathroom can transfer it to anything they touch. Outbreaks have been traced to salads, fresh fruit, sandwiches, pastry icing, and glazed baked goods.
Fresh produce is another major category. Fruits and vegetables can pick up the virus from the hands of infected workers in the field, from irrigation water tainted with sewage, or during processing and packaging. Frozen raspberries, frozen strawberries, iceberg lettuce, green onions, and tomatoes have all been linked to outbreaks. Even something as simple as removing strawberry stems by hand during picking can introduce contamination.
Shellfish carry a particular risk because they filter large volumes of water and concentrate whatever is in it. Oysters, clams, mussels, and cockles harvested near sewage discharge or from illegally harvested beds have caused some of the largest hepatitis A outbreaks on record, with individual events affecting thousands of people. Steaming shellfish to an internal temperature of 85°C to 90°C (about 185°F to 194°F) for at least 90 seconds inactivates the virus, but eating them raw or lightly cooked leaves the risk intact.
Contaminated Water
Hepatitis A can remain infectious in fresh or salt water for up to 12 months, making contaminated water a persistent source of outbreaks. In the United States, untreated groundwater has been responsible for 72% of drinking water outbreaks linked to the virus. The pattern is consistent: private wells and springs that aren’t subject to federal drinking water standards and have no disinfection system in place.
Groundwater becomes contaminated when nearby septic systems leak, when sewage seeps in after heavy rainfall, or when wells are poorly constructed or maintained. Certain types of geology, like karst limestone with its underground channels, allow pathogens to travel rapidly through the ground into water supplies. Since the mid-1990s, every hepatitis A drinking water outbreak reported in the U.S. involved an individual water system using untreated groundwater.
Person-to-Person Contact
Living in a household with someone who has hepatitis A is a significant risk factor. The virus spreads when an infected person prepares food with unwashed hands or when shared surfaces pick up traces of contamination. Casual contact, like being in the same room, does not spread the virus. It requires actual ingestion of viral particles.
Sexual contact is another route, particularly oral-anal contact. Men who have sex with men face elevated risk, and large outbreaks in this population have been documented in multiple high-income countries in recent years. Using condoms, dental dams, and thorough hygiene practices reduces the risk during sexual activity.
Why the Virus Spreads So Easily
Hepatitis A is unusually hardy for a virus. On hard indoor surfaces, it can survive for days. At refrigerator temperature (around 5°C), its half-life on surfaces exceeds four days. At room temperature with low humidity, the half-life stretches to nearly eight days. It survives freezing, resists many chemical disinfectants, and is not reliably killed by standard pasteurization temperatures. Common fruit and vegetable rinses, while effective against bacteria, do much less against this virus.
The virus also persists for days to weeks in dried feces and survives for several hours on human hands. This durability is part of why a single infected food handler can trigger an outbreak affecting dozens of people.
The Contagious Window
The incubation period for hepatitis A averages 28 days, with a range of 15 to 50 days. That’s a long stretch of feeling fine before any symptoms appear. The critical detail: infected people are most contagious one to two weeks before symptoms start, when viral concentration in stool is at its peak. By the time someone develops jaundice, fatigue, or nausea, they’ve likely already been spreading the virus for weeks. Virus shedding can continue for up to three weeks after symptoms begin.
This timeline is especially important when it comes to children. Among children younger than 6, 70% of infections produce no symptoms at all. A child can carry and shed the virus for weeks without anyone realizing they’re infected, making young children a common, invisible link in transmission chains within families and childcare settings.
Who Faces the Highest Risk
Travelers to regions with high rates of hepatitis A top the list. Parts of Africa and Asia have high endemicity, while parts of Central and South America, other areas of Asia, and eastern Europe fall into the intermediate category. Risk increases for travelers who visit rural areas, hike in backcountry settings, or eat and drink in places with poor sanitation.
Within the United States, recent outbreak patterns have shifted. Since 2016, widespread outbreaks driven by person-to-person spread have disproportionately affected adults who use drugs and people experiencing homelessness. In 2023, there were 1,648 reported hepatitis A cases and an estimated 3,300 total infections after accounting for underreporting, with 85 hepatitis A-related deaths. Other groups at elevated risk include sexual partners of infected individuals, men who have sex with men, and anyone living with an infected household member.
How Vaccination Prevents Infection
The hepatitis A vaccine is highly effective. A randomized controlled trial measured its protective efficacy at 94%, and in trials with children ages 2 through 16, 100% of those vaccinated developed protective antibodies. The immunity is also remarkably long-lasting: 95% to 100% of vaccinated people still have protective antibody levels 15 to 20 years after vaccination. One study estimated that 95% or more of vaccinated individuals would retain protection for at least 30 years, and 90% or more for 40 years.
For travelers heading to areas with intermediate or high endemicity, vaccination before departure is the most reliable protection. The vaccine is also recommended for all children at age 1, for people who use drugs, for those experiencing homelessness, and for anyone with chronic liver disease who would face more severe consequences from infection. Beyond vaccination, thorough handwashing after using the bathroom and before preparing food remains the simplest and most effective way to interrupt the fecal-oral chain that keeps this virus circulating.