Hepatitis A spreads through the fecal-oral route, meaning the virus enters your body when you swallow something contaminated with feces from an infected person. This can happen through contaminated food, water, or direct contact with someone who is infectious. Unlike hepatitis B and C, hepatitis A does not spread through blood and is not a chronic infection, but it is highly contagious in close settings like households, where secondary infection rates reach 20% to 50% without preventive treatment.
The Fecal-Oral Route
The hepatitis A virus (HAV) leaves the body in stool and survives well enough in the environment to reach a new host through several pathways. You don’t need to come into direct contact with feces. Microscopic amounts on hands, food, surfaces, or in water are enough. Once you swallow the virus, it travels through your digestive tract, infects liver cells, and begins replicating. You then start shedding the virus in your own stool before you even feel sick.
This is what makes hepatitis A so efficient at spreading: a person is most contagious during the one to two weeks before symptoms appear. By the time someone develops the telltale jaundice or fatigue, they may have already passed the virus to others through ordinary activities like preparing meals or sharing a bathroom.
Contaminated Food and Shellfish
Food is one of the most common vehicles for hepatitis A. The list of foods linked to outbreaks is long: shellfish, salads, fresh fruits, vegetables, sandwiches, frozen juices, ice cream, and other items eaten raw or lightly cooked. Contamination happens in a few ways. Fruits and vegetables can be grown in fields irrigated with water tainted by sewage. Shellfish like oysters and mussels filter large volumes of water and concentrate the virus when harvested from polluted areas. And at any point along the supply chain, an infected food handler with poor hand hygiene can transfer the virus to ready-to-eat foods.
Recent U.S. outbreaks illustrate the range: imported pomegranate seeds in 2013, imported frozen strawberries and raw scallops in 2016, and fresh blackberries in 2019 all caused multi-state clusters. Cooking does kill the virus, but it requires temperatures above 85°C (185°F) sustained for at least one minute. That means lightly steamed shellfish or briefly rinsed produce may not be safe if the virus is present.
Contaminated Water
Drinking water has historically been a major source of hepatitis A, particularly in areas without modern water treatment. A CDC analysis covering outbreaks from 1971 to 2017 found that untreated groundwater was linked to 72% of drinking water-associated hepatitis A outbreaks, causing roughly 68% of reported cases. The contamination typically comes from nearby septic systems, sewage leaks, heavy rainfall washing waste into wells, or geological features like porous limestone that allow pathogens to travel quickly underground.
Federal water safety rules introduced in the late 1980s and 2000s have largely eliminated outbreaks from public water systems in the U.S. No hepatitis A outbreaks linked to community water sources have been reported since 1990. The remaining risk falls on private wells and individual water systems, which are not required to meet national drinking water standards and often have little or no treatment. If you rely on well water, proper construction, maintenance, and periodic testing are your main lines of defense.
Person-to-Person and Sexual Transmission
Direct contact with an infected person is the other major pathway. In families, this commonly happens when someone with the virus prepares food for others without thorough handwashing. Young children are especially effective spreaders because they often have mild or no symptoms, so no one realizes they’re infected, yet they shed high amounts of virus. Household secondary attack rates of 20% to 50% reflect just how readily the virus passes between people sharing living spaces.
Sexual transmission is also well documented, particularly through oral-anal contact. The WHO has classified the risk of person-to-person sexual transmission as moderate to high. Several large outbreaks in Europe and the Americas since 2017 have predominantly affected men who have sex with men, with oral-anal contact identified as the primary risk factor. Casual contact like handshakes or sitting near someone does not spread the virus.
Who Is Most at Risk Today
The profile of hepatitis A outbreaks in the United States has shifted over the past decade. Since late 2016, widespread outbreaks have spread primarily through person-to-person contact among people experiencing homelessness or reporting drug use. These community outbreaks have been prolonged and difficult to control, partly because the affected populations have less access to vaccination and sanitation. In 2022, the CDC estimated about 4,500 hepatitis A infections in the U.S., a 32% drop from the 2017 baseline but still above elimination targets.
Travelers to countries with high rates of hepatitis A also face elevated risk, particularly in parts of Central and South America, Africa, Asia, and Eastern Europe where sanitation infrastructure is less reliable. In these settings, contaminated water and food are the dominant routes of exposure.
How to Reduce Your Risk
Vaccination is the most effective protection. Two doses provide long-lasting immunity, and the vaccine can even prevent infection after exposure if given within two weeks of contact with the virus. For people with weakened immune systems or chronic liver disease, an additional injection of immune globulin alongside the vaccine offers extra protection during that 14-day window.
Beyond vaccination, prevention comes down to basic hygiene and food safety. Thorough handwashing with soap and water after using the bathroom, changing diapers, and before preparing food interrupts the fecal-oral chain. When traveling in areas with questionable water safety, stick to bottled or boiled water, avoid ice, and eat foods that are fully cooked and served hot. Shellfish should be cooked thoroughly, not just steamed until the shell opens. Peeling your own fruit is safer than eating pre-cut produce.
If someone in your household is diagnosed, everyone else in the home who isn’t already vaccinated should receive the vaccine as quickly as possible. The 20% to 50% household transmission rate drops dramatically with prompt post-exposure vaccination.