How Hepatitis A is Transmitted
Hepatitis A is primarily transmitted through the fecal-oral route, when small amounts of fecal matter from an infected person are ingested by another person through contaminated food, water, or direct personal contact.
Primary Modes of Transmission
- Person-to-person transmission through the fecal-oral route is the most common way hepatitis A virus (HAV) spreads in the United States, especially among close contacts in household and extended family settings 1.
- Children play a key role in transmission as they often have asymptomatic or unrecognized infections but can still spread the virus to others 1.
- In households with an adult HAV infection of unknown source, studies found that 52% included a child under 6 years of age, and 25-40% of these young children showed evidence of acute HAV infection 1.
Food and Water Transmission
- Common-source outbreaks occur through exposure to fecally contaminated food or water 1.
- Uncooked foods are frequently identified as sources of outbreaks 1.
- Cooked foods can transmit HAV if cooking is inadequate (temperatures below 185°F/85°C) or if food is contaminated after cooking, which commonly happens in outbreaks associated with infected food handlers 1.
- Waterborne outbreaks are rare in countries with well-maintained sanitation systems but can occur with sewage-contaminated or inadequately treated water 1.
Environmental Persistence
- HAV can remain stable in the environment for months under certain conditions 1.
- To inactivate the virus, foods must be heated to temperatures above 185°F (85°C) for at least 1 minute 1.
- Surfaces can be disinfected using a 1:100 dilution of sodium hypochlorite (household bleach) in tap water 1.
High-Risk Populations and Settings
- Injection drug users have higher rates of HAV infection, with transmission occurring through fecal contamination of drug paraphernalia and close personal contact 1.
- Men who have sex with men (MSM) experience frequent outbreaks, with transmission associated with oral-anal contact and multiple sex partners 1.
- Foodborne transmission accounts for a relatively small proportion of reported cases in the United States but can lead to widespread outbreaks when an infected food handler contaminates food 1, 2.
Less Common Transmission Routes
- On rare occasions, HAV has been transmitted through blood transfusions or blood products collected from donors during their viremic phase 1.
- While HAV has been detected in saliva during the incubation period in experimental studies with non-human primates, transmission by saliva has not been demonstrated in humans 1.
Period of Infectivity
- Peak infectivity occurs during the 2-week period before the onset of jaundice or liver enzyme elevation, when the concentration of virus in stool is highest 1.
- People are most infectious from approximately 14 to 21 days before to about 8 days after the onset of jaundice 1, 3.
- Children can shed the virus for up to 10 weeks after onset of clinical illness 1, 3.
Important Considerations
- Unlike hepatitis B and C, hepatitis A is not typically transmitted through percutaneous exposure (needle sticks) 1, 4.
- Approximately 45-50% of patients have no identified source for their infection, highlighting the challenge of tracing transmission routes 1.
- International travel to areas with endemic hepatitis A is an important risk factor, particularly for children visiting family members in countries with high HAV prevalence 1, 5.