Hepatitis A and hepatitis E are the two hepatitis viruses spread through feces. Both travel what public health experts call the fecal-oral route, meaning the virus leaves one person’s body in stool and enters another person’s mouth, usually through contaminated water or food.1PubMed Central. Enteric hepatitis viruses The other well-known hepatitis viruses, B and C, spread through blood and bodily fluids and are fundamentally different in how they move between people. Despite sharing a transmission route, hepatitis A and E differ in where they cause the most harm, who is most vulnerable, and how well we can prevent them.
How the Fecal-Oral Route Actually Works
The fecal-oral route sounds dramatic, but it rarely involves anything as obvious as direct contact with stool. In practice, it usually means microscopic amounts of virus from an infected person’s feces end up in water supplies, on food, or on surfaces, and someone else swallows them without realizing it. Hepatitis A, for example, can spread when an infected food handler with poor hand hygiene touches produce or prepared dishes. Studies have shown that casual contact between contaminated hands and clean food can transfer as much as a tenth of the infectious virus present on those hands.2PubMed Central. Foodborne spread of hepatitis A: Recent studies on virus survival, transfer and inactivation The virus also persists for hours on hands and for days on indoor surfaces, making shared bathrooms and crowded institutional settings natural hotspots.
Both hepatitis A and E viruses are shed in feces as tough, membrane-free particles that survive well outside the body. This environmental hardiness is what makes them so good at epidemic spread. Inside the bloodstream, however, these same viruses actually circulate wrapped in a protective membrane borrowed from the host’s own cells. That membrane gets stripped away as the virus passes through the bile duct into the intestine, leaving behind a naked, durable particle that can withstand the harsh conditions of sewage, soil, and water.3PubMed Central. Naked Viruses That Aren’t Always Naked: Quasi-Enveloped Agents of Acute Hepatitis This biological trick is one reason both viruses have caused massive waterborne outbreaks in places with inadequate sanitation.
Hepatitis A and Its Common Vehicles
Hepatitis A virus (HAV) is probably the most familiar fecally-transmitted hepatitis worldwide. Transmission happens through direct person-to-person contact with an infected individual or through contaminated food and water.4Clinical Infectious Diseases. Hepatitis A Transmitted by Food Outbreaks pop up most often in hospitals, daycare centers, schools, and food-service settings, anywhere that large numbers of people share facilities and meals.2PubMed Central. Foodborne spread of hepatitis A: Recent studies on virus survival, transfer and inactivation
One of the trickiest aspects of hepatitis A is the timing. People shed the virus in their stool most heavily before they feel sick or show any symptoms like jaundice. Viral shedding can continue for weeks after liver enzymes peak. In one study, researchers found detectable virus in stool samples for up to about three and a half weeks after peak liver inflammation using one method, and viral genetic material remained detectable for nearly two months using more sensitive testing.5PubMed Central. Excretion of hepatitis A virus (HAV) in adults: comparison of immunologic and molecular detection methods and relationship between HAV positivity and infectivity in tamarins That extended window means a person can be spreading the virus at work or at home long after they think the worst is over.
Imported fruits and vegetables eaten raw have been directly linked to outbreaks, since the virus can survive on produce for days. Shellfish, particularly bivalves like mussels and oysters that filter large volumes of water, are another well-recognized vehicle. These animals can concentrate viral particles from sewage-tainted water in their tissues.6PubMed. Quantitative levels of norovirus and hepatitis A virus in bivalve molluscs collected along the food chain in the Netherlands, 2013-2017 Cooking helps, but the virus is surprisingly heat-resistant. Research on blue mussels found that at an internal temperature of about 72°C (roughly 162°F), it still took over seven minutes of sustained heating to reduce HAV by a factor of a million.7PubMed Central. Determination of thermal inactivation kinetics of hepatitis A virus in blue mussel (Mytilus edulis) homogenate A quick steam that barely opens the shell is not enough.
Hepatitis E and Its Surprising Range
Hepatitis E virus (HEV) shares the fecal-oral route with hepatitis A but has a split personality depending on where in the world you encounter it. In developing countries, especially in South Asia and sub-Saharan Africa, genotypes 1 and 2 cause large waterborne outbreaks tied to contaminated drinking water and poor sanitation.8PubMed. The global burden of hepatitis E outbreaks: a systematic review These outbreaks can affect thousands of people at once and are particularly devastating in refugee camps and flood-affected areas where clean water is scarce.
In Europe and other industrialized regions, hepatitis E looks completely different. The dominant strain, genotype 3, is zoonotic, meaning it jumps from animals to humans. Pigs are the main reservoir. A study of food products containing raw pork liver in France found the virus in anywhere from 3% to 30% of samples tested, depending on the product category, and genetic analysis showed these viral strains closely matched sequences found in both humans and swine.9PubMed Central. Frequent hepatitis E virus contamination in food containing raw pork liver, France In Belgium, zoonotic genotype 3 infections linked to contaminated pork are now the leading cause of acute viral hepatitis.10PubMed. Hepatitis E virus in pork meat products and exposure assessment in Belgium Foods like pâté, dried sausages made with liver, and undercooked pork are the most common culprits. This means hepatitis E in wealthy countries is not really a sanitation problem but a food-safety one.
Why Hepatitis B and C Do Not Spread This Way
People sometimes assume all hepatitis viruses spread the same way, but that is not the case. Hepatitis B and C are bloodborne. They spread through shared needles, unscreened blood transfusions, sexual contact, and from mother to child during birth. The fecal-oral route simply does not work for them. Researchers have directly tested this for hepatitis B: in an experiment using chimeric mice, fecal samples from patients with chronic hepatitis B were sterilized and given to the animals both orally and intravenously, and no infection resulted, even though the stool contained detectable levels of HBV genetic material.11PubMed Central. Lack of infectivity of HBV in feces from patients with chronic hepatitis B virus infection, and infection using chimeric mice Hepatitis B and C viruses lack the environmental durability that makes fecal-oral spread possible. They are fragile outside the body compared to the hardy, naked particles that hepatitis A and E shed into stool.
This distinction matters practically. If someone in your household has hepatitis B or C, you do not need to worry about sharing a toilet. If someone has hepatitis A, you do. The hygiene measures that protect you from each type of hepatitis are fundamentally different.
How Illness Differs Between Hepatitis A and E
Both infections are typically acute, meaning they cause a short-term illness rather than a lifelong one. Hepatitis A almost never becomes chronic. The vast majority of patients recover fully with supportive care alone.12PubMed Central. Natural History, Clinical Manifestations, and Pathogenesis of Hepatitis A Symptoms vary dramatically by age, though. Children with hepatitis A often have no symptoms at all, while adults tend to develop jaundice, abdominal pain, and dark urine.13PubMed Central. Hepatitis A: Epidemiology, Natural History, Unusual Clinical Manifestations, and Prevention This age-dependent pattern has an ironic public health consequence: in countries where children are routinely exposed early, most get through it asymptomatically and are immune for life. As sanitation improves and fewer children encounter the virus, more adults remain susceptible, and adults get sicker.
Hepatitis E is also usually mild and self-limiting in most young adults.14PubMed Central. A Study of Hepatitis E in Pregnancy: Maternal and Fetal Outcome But it has one devastating exception. Pregnant women, especially in the second and third trimesters, face a dramatically higher risk of severe illness, including fulminant liver failure.15PubMed Central. Hepatitis E infection during pregnancy This heightened severity in pregnancy is unique among the hepatitis viruses and is one of the main reasons hepatitis E outbreaks in developing countries can be so lethal. The exact reasons why pregnancy makes hepatitis E so much worse remain an active area of research, but immunological changes during pregnancy that normally protect the fetus seem to leave the mother more vulnerable to the virus.
Chronic Hepatitis E in Organ Transplant Recipients
For years, hepatitis E was considered strictly an acute disease, like hepatitis A. That understanding changed when researchers discovered that organ transplant recipients could develop chronic hepatitis E infections. In a landmark study, 14 cases of acute HEV infection were identified among liver, kidney, and kidney-pancreas transplant patients. Chronic hepatitis, confirmed by persistently elevated liver enzymes and ongoing viral presence, developed in over half of them. Patients who progressed to chronic disease had lower counts of key immune cells, suggesting that the depth of immune suppression was a driving factor.16PubMed. Hepatitis E virus and chronic hepatitis in organ-transplant recipients
A larger follow-up study confirmed the pattern: about two-thirds of solid organ transplant patients with hepatitis E went on to develop chronic infection. The type of immunosuppressive drug mattered. Patients on tacrolimus-based regimens were more likely to develop chronic disease than those on cyclosporin A. Encouragingly, about a third of chronic cases cleared the virus when their immunosuppressive therapy was reduced.17Gastroenterology. Factors Associated With Chronic Hepatitis in Patients With Hepatitis E Virus Infection Who Have Received Solid Organ Transplants This finding has real clinical importance: if you are a transplant recipient and develop unexplained liver inflammation, your doctor should consider hepatitis E, even in a wealthy country where the infection is often overlooked.
Diagnosis Can Be Trickier Than You Would Expect
Hepatitis A is usually diagnosed with a straightforward blood test looking for antibodies your immune system makes against the virus. Hepatitis E, on the other hand, can be harder to pin down. The recommended approach for suspected cases combines antibody testing with direct detection of viral genetic material in the blood.18PubMed Central. A Review of the Diagnosis and Management of Hepatitis E This dual strategy is necessary because antibody tests for hepatitis E are less reliable than those for hepatitis A, and in immunocompromised patients the antibody response may be weak or absent. In many Western countries, hepatitis E simply is not on the radar of most clinicians, which means it goes undiagnosed more often than it should.
Vaccines and Prevention
Hepatitis A is one of the great vaccine success stories. Safe, highly effective vaccines have been available since the mid-1990s, and childhood vaccination programs have slashed infection rates in countries that adopted them. The vaccine even works remarkably well after exposure. In outbreak settings, vaccination given to people who had already been exposed prevented about 98% of expected infections, a rate on par with the older approach of injecting immune globulin, which provides only short-term borrowed antibodies.19PubMed Central. Effectiveness of hepatitis A vaccination as post-exposure prophylaxis A head-to-head trial confirmed that the vaccine offers good post-exposure protection, with the added advantage of conferring long-term immunity rather than a temporary shield.20PubMed. Hepatitis A vaccine versus immune globulin for postexposure prophylaxis
Hepatitis E vaccines are a different story. Only one, marketed as Hecolin, has been licensed, and as of 2025 it is approved only in China and Pakistan.21PubMed. Hepatitis E vaccine landscape update 2025 Clinical trials showed high efficacy and cross-genotype protection, but significant data gaps remain. The vaccine has not been adequately studied in the populations that need it most: pregnant women, young children, and immunocompromised individuals. Without World Health Organization prequalification, global distribution remains limited.22PubMed Central. Hepatitis E virus: Current epidemiology and vaccine This is a frustrating situation given how dangerous hepatitis E can be during pregnancy in endemic regions.
In the absence of widespread HEV vaccination, prevention relies on clean water, proper sanitation, and food safety. For the zoonotic strains common in Europe, that means thoroughly cooking pork products, especially anything containing liver. For waterborne strains in endemic areas, it means the same infrastructure investments that prevent cholera and typhoid: treated drinking water and functional sewage systems.
Travel and Who Faces the Highest Risk
Travelers to regions with poor sanitation are a classic at-risk group for both hepatitis A and E. Hepatitis A vaccination is standard pre-travel advice for anyone heading to endemic areas. Hepatitis E is harder to protect against, and a two-decade analysis of travel-related HEV infections found that tourists made up half of all cases. Many of these travelers had not sought any pre-travel medical advice, and adherence to food and water precautions was particularly poor among younger and long-term travelers. Some patients with travel-related hepatitis E also had a concurrent gastrointestinal infection, reinforcing that the virus enters through contaminated food and water.23PubMed Central. Travel-related hepatitis E: a two-decade GeoSentinel analysis
Beyond travelers, people experiencing homelessness and those who use injection drugs have been hit by hepatitis A outbreaks in recent years, particularly in the United States. These outbreaks spread through person-to-person contact in settings where hand hygiene and sanitation access are limited. For hepatitis E, the highest-risk groups in wealthy countries are people who eat raw or undercooked pork and organ transplant recipients on immunosuppressive drugs.
Tracking These Viruses in Wastewater
Because both viruses are shed in feces, sewage monitoring offers a window into how widely they circulate in a population. A multi-country study of untreated wastewater across six Asian nations illustrates how the two viruses occupy different ecological niches. In Nepal, half of wastewater samples tested positive for hepatitis A but only 2% for hepatitis E. Japan showed the opposite pattern: hepatitis A appeared in just 1% of samples, while hepatitis E turned up in nearly a quarter. Vietnam and the Philippines had only hepatitis E, while Indonesia had only hepatitis A.24PubMed Central. Prevalence of hepatitis A and E viruses in wastewater in Asian countries These patterns reflect each country’s sanitation infrastructure, vaccination coverage, dietary habits, and the local animal reservoirs for hepatitis E. Japan’s high HEV rate, for instance, aligns with its consumption of raw and lightly cooked pork and wild game.
Wastewater surveillance is increasingly valued as an early warning system. A spike in viral RNA in sewage can signal a building outbreak weeks before clinical cases show up in hospitals. The same approach gained visibility during the COVID-19 pandemic and is now being extended to other fecally-shed pathogens, including hepatitis A and E.
How Hepatitis A Was First Identified in Stool
The distinction between fecally-transmitted and blood-transmitted hepatitis has a surprisingly recent history. During World War II, military doctors noticed that some hepatitis cases seemed linked to contaminated food and water while others followed blood transfusions or injections with reused needles. It took decades to sort out the virology. After hepatitis B was identified through the discovery of the Australia antigen in blood, researchers tried to find hepatitis A using the same blood-focused methods and kept failing. The breakthrough came when investigators shifted their search from serum to feces and applied new detection techniques, finally visualizing the virus in stool samples in the early 1970s.25PubMed Central. History of the Discovery of Hepatitis A Virus Hepatitis E was recognized even later, in the 1980s, after outbreaks of waterborne hepatitis that did not match either A or B.
The fact that it took researchers so long to look in the right place underscores a broader lesson about these viruses. They hide in plain sight. Their particles are tiny, environmentally tough, and shed in enormous quantities by people who may not feel sick yet. Understanding that hepatitis A and E are fecal viruses, and that B and C are not, remains one of the most practically useful distinctions in infectious disease. It determines whether the risk is in your water supply or in your bloodstream, and it shapes everything from vaccine recommendations to outbreak investigation strategies.