Hepatitis A spreads through what’s called the fecal-oral route, meaning the virus enters your body when you ingest something contaminated with fecal matter from an infected person. That sounds dramatic, but in practice it happens through surprisingly ordinary things: eating food prepared by someone who didn’t wash their hands well, drinking contaminated water, or having close contact with someone who’s infected. An estimated 3,300 new infections occurred in the United States in 2023 alone.
The Fecal-Oral Route in Everyday Life
Hepatitis A virus lives in the stool of infected people. When even microscopic traces of contaminated feces reach your mouth, the virus can take hold. This doesn’t require dramatic unsanitary conditions. It often happens through a chain of small events: an infected person uses the bathroom, doesn’t wash their hands thoroughly, then touches food or a surface you later touch before eating.
The virus is also remarkably sturdy in the environment. Research on contaminated produce found that at refrigerator temperatures (around 3°C), the virus takes roughly 30 days to lose just 90% of its infectious potential. At room temperature, that drops to about 5 days. This means contaminated food can remain infectious for days or even weeks, especially when kept cold, which is exactly how most fresh produce is stored and shipped.
Foods and Water Most Linked to Infection
According to the FDA, the foods most frequently tied to hepatitis A transmission are shellfish, raw vegetables, fruit (especially berries), and salads. Shellfish are a particular concern because filter-feeding animals like oysters and mussels concentrate the virus from contaminated water in their tissues. Eating them raw or undercooked is one of the most well-documented food sources of infection.
Raw produce becomes a risk when it’s irrigated, washed, or handled using water that carries the virus, or when an infected worker touches it during harvesting or preparation. Berries have been linked to multiple outbreaks, partly because they’re often eaten without cooking. Salads carry similar risk since the ingredients are consumed raw and handled by multiple people during preparation.
Contaminated drinking water is a major transmission route in countries with less developed sanitation infrastructure. In the U.S. and other high-income countries, municipal water treatment makes waterborne transmission rare, but it remains a real concern for travelers.
Person-to-Person Spread
Direct contact with an infected person is actually the most common way hepatitis A spreads in the United States. This includes household contact, sexual contact (particularly oral-anal contact), and sharing drugs or drug preparation equipment. The virus can spread through any situation where traces of an infected person’s stool might reach another person’s mouth, even indirectly.
What makes person-to-person spread especially effective is the timing. An infected person is most contagious before they even know they’re sick. The virus sheds heavily in stool during the two weeks before symptoms appear, so people unknowingly pass it to others through normal daily activities during that window. By the time someone develops jaundice or feels ill, they’ve already had their peak period of contagiousness.
How Long Before You Feel Sick
After exposure, the average incubation period is 28 days, though it can range from 15 to 50 days. During much of that time, the virus is silently replicating in your liver and shedding in your stool. Symptoms, when they do appear, typically include fatigue, nausea, abdominal pain, loss of appetite, and jaundice (yellowing of the skin and eyes).
Not everyone develops obvious symptoms. Children under six often have no symptoms at all, while most infected adults do get noticeably ill. Regardless of symptoms, anyone infected can spread the virus to others.
Who Faces the Highest Risk
Certain situations put you at greater risk of exposure. Traveling to countries where hepatitis A is common, particularly parts of Central and South America, Africa, and Asia, is one of the most recognized risk factors. Using recreational drugs, whether injected or not, increases risk because of the close personal contact and shared equipment involved. People experiencing homelessness face elevated risk due to limited access to sanitation. Men who have sex with men are also at higher risk due to specific sexual practices.
Anyone who has close contact with a person already diagnosed with hepatitis A is at immediate risk and may benefit from post-exposure vaccination.
How Hepatitis A Is Confirmed
A blood test is the only way to confirm hepatitis A. The key marker is a specific type of antibody called IgM anti-HAV, which your immune system produces in the early phase of infection. This antibody typically appears 5 to 10 days before symptoms start and remains detectable for about six months after infection.
A different antibody, IgG anti-HAV, appears around the time symptoms begin and stays in your blood for life. Its presence means you’re immune, either from a past infection or from vaccination. If your doctor suspects an active infection, the IgM test is the one that matters. The IgG test on its own can’t distinguish between someone who’s currently sick and someone who was vaccinated years ago.
Vaccination Offers Near-Complete Protection
The hepatitis A vaccine is highly effective. More than 95% of adults develop protective antibodies within four weeks of a single dose, and nearly 100% are fully protected after the second dose. For children and adolescents, the numbers are even better: over 97% develop protection after just the first dose, and clinical trials found 100% protection after two doses in people aged 2 to 18.
The protection lasts a long time. Studies have tracked antibody levels for at least 25 years in people vaccinated as children and at least 20 years in people vaccinated as adults, with detectable immunity still intact. Mathematical modeling suggests protection likely persists for 40 years or longer, and possibly for life. The two-dose series, spaced six months apart, is the standard recommendation and provides the most durable protection.
Other Ways to Reduce Your Risk
Beyond vaccination, the same basic hygiene practices that prevent many infections also work against hepatitis A. Thorough handwashing with soap and water after using the bathroom and before handling food is the single most effective daily habit. When traveling to areas with higher rates of hepatitis A, sticking to bottled or boiled water, avoiding ice, and eating only cooked foods or fruits you peel yourself significantly cuts your exposure.
Cooking food to high temperatures kills the virus, so thoroughly cooked shellfish and vegetables carry far less risk than raw preparations. Given the virus’s ability to survive for weeks on refrigerated produce, cooking is a more reliable safeguard than washing alone for high-risk foods.