Hepatitis A and E: Transmission Risk in Travel

Hepatitis A and hepatitis E are viral infections of the liver transmitted predominantly by the faecal-oral route, through food and water contaminated with human or, for some hepatitis E genotypes, animal sources. Both are relevant to travel because exposure risk rises in regions with limited sanitation, making them important examples of enterically transmitted infection in travelers.

Definition

Hepatitis A and hepatitis E are acute, usually self-limiting viral hepatitides caused respectively by the hepatitis A virus (a picornavirus) and the hepatitis E virus (a hepevirus), both spread mainly by the faecal-oral route via contaminated food and water, with travel to higher-incidence regions a recognized exposure pathway.

Scope

This entry covers how hepatitis A and hepatitis E viruses are transmitted, the geography of travel-related exposure, and the contrasting risk profiles of the two viruses, including the age-dependent severity of hepatitis A and the particular concern of hepatitis E in pregnancy. It is a reference overview of transmission and risk patterns; it is framed around exposure rather than individualized prophylaxis or treatment.

Core questions

• How are hepatitis A and hepatitis E transmitted, and how does that shape travel risk?
• How do the two viruses differ in geography, reservoir, and severity profile?
• Why is hepatitis E of particular concern in pregnancy?

Key concepts

• Faecal-oral transmission
• Hepatitis A virus (picornavirus)
• Hepatitis E virus (hepevirus)
• Contaminated food and water
• Age-dependent severity of hepatitis A
• Hepatitis E in pregnancy
• Zoonotic hepatitis E genotypes

Mechanisms

Both viruses are ingested in contaminated food or water, replicate in the liver, and produce an acute hepatitis that is typically self-limiting in otherwise healthy people. Hepatitis A severity rises with age at infection, so it is often mild or asymptomatic in young children but more clinically significant in adults, including some travelers from low-incidence settings. Hepatitis E includes waterborne epidemic genotypes in endemic regions and zoonotic genotypes elsewhere; it is generally self-limiting but carries a notably higher risk of severe disease in pregnancy and can become chronic in immunocompromised hosts.

Clinical relevance

For travel medicine, hepatitis A and E illustrate how faecal-oral exposure links destination, food and water hygiene, and host factors to infection risk, and they are standard considerations in pre-travel risk discussions. The entry describes transmission and risk patterns at a reference level and is not a source of individualized advice on immunization schedules or clinical management.

Epidemiology

Hepatitis A incidence is highest where sanitation is limited, producing a contrast between high-endemicity regions, where most exposure occurs in childhood, and low-endemicity settings, where susceptible adults may be exposed during travel. Hepatitis E causes large waterborne outbreaks in some endemic regions and sporadic, often zoonotic, infection elsewhere; both viruses appear among causes of hepatitis and febrile illness in returned-traveler data.

Evidence & guidelines

Comprehensive reviews such as Lemon and colleagues (2018) characterize the virology and changing epidemiology of the enterically transmitted hepatitis viruses, and Kamar and colleagues (2012) synthesize hepatitis E specifically, including its severity in pregnancy and chronicity in immunosuppression. These sources describe transmission, risk, and evidence at a reference level rather than prescribing prophylaxis or treatment here.

History

Hepatitis A was distinguished from other forms of viral hepatitis and its virus characterized in the twentieth century, after which inactivated vaccines transformed the prevention landscape. Hepatitis E was recognized more recently, initially through investigation of waterborne 'enterically transmitted non-A, non-B hepatitis' outbreaks, and later understood to include zoonotic transmission and chronic infection in immunocompromised people; both are now framed as emerging or re-emerging enterically transmitted hepatitis viruses.

Debates

How should the zoonotic and chronic dimensions of hepatitis E be weighed?

The recognition that some hepatitis E genotypes are zoonotic and that the virus can cause chronic infection in immunocompromised hosts has broadened its perceived significance beyond classic waterborne outbreaks, with ongoing discussion of surveillance and risk framing.

Key figures

• Stanley M. Lemon
• Nassim Kamar
• Harry R. Dalton
• Pierre Van Damme

Seminal works

• lemon-2018
• kamar-2012

Frequently asked questions

How are hepatitis A and hepatitis E spread during travel?

Both are transmitted mainly by the faecal-oral route through food and water contaminated with the virus, so risk rises with travel to regions where sanitation is limited; some hepatitis E genotypes also have zoonotic (animal-associated) transmission.

Why is hepatitis E a special concern in pregnancy?

Hepatitis E is usually self-limiting, but reviews describe a substantially higher risk of severe disease and poor outcomes when infection occurs during pregnancy, which is why it is highlighted separately from hepatitis A.