Hepatitis A

Key takeaways

• Childhood vaccine: 2 doses, starting at 12 to 23 months, given 6 months apart
• Adults who should be vaccinated: travelers to many countries, people at higher risk, and any adult who wants protection
• Most useful single change: Check whether you and your children have had both doses.
• Commonest mistake: Preparing food for others while you have symptoms.
• See a doctor if any of the signs under "When to get help" below apply to you.

Why it matters

It can cause weeks of illness and, rarely, liver failure, and it is preventable with a safe, effective vaccine.

The numbers, in one place

Published figures for Hepatitis A

Measure	Figure
Childhood vaccine	2 doses, starting at 12 to 23 months, given 6 months apart
Adults who should be vaccinated	travelers to many countries, people at higher risk, and any adult who wants protection
Time from exposure to symptoms	about 15 to 50 days
After an exposure	vaccine or immune globulin within 2 weeks can help prevent illness
Chronic infection	does not occur; most people recover fully

What helps

• Check whether you and your children have had both doses
• Ask about the vaccine at least a few weeks before international travel
• Wash hands with soap and water after using the toilet or changing diapers and before handling food
• Call your doctor or health department quickly after a known exposure

What to avoid

• Preparing food for others while you have symptoms
• Drinking alcohol or taking extra acetaminophen (Tylenol) while your liver is inflamed, unless your doctor agrees
• Drinking untreated water or eating raw shellfish where hepatitis A is common

In depth

Hepatitis A virus enters through the mouth, passes through the gut and travels to the liver, where it multiplies inside liver cells. It is the immune system's attack on those infected cells, rather than the virus itself, that causes most of the inflammation and symptoms. The virus is shed into bile and passed in stool, often for a couple of weeks before symptoms appear, which is why people spread it before they know they are ill.

How sick someone gets depends a lot on age. Many young children have no symptoms or only a mild illness, so they can quietly pass the virus to others at home or in child care. Most adults do develop symptoms, which can last for weeks, and a small number have a relapse during recovery. Older adults and people with existing liver disease have the highest risk of serious illness.

Unlike hepatitis B and C, hepatitis A never becomes a long-term infection, and recovery brings lifelong immunity. Rarely, it causes sudden liver failure. In recent years, large US outbreaks have spread person to person among people who use drugs and people experiencing homelessness, which is why vaccination is now recommended for these groups as well as for travelers and children.

Signs and symptoms

• Tiredness and loss of appetite, often the first symptoms
• Nausea, vomiting and pain in the upper right part of the belly
• Fever and joint aches
• Dark, tea-colored urine and pale or clay-colored stool
• Yellowing of the skin or the whites of the eyes (jaundice)
• Itchy skin as the illness goes on

Causes and risk factors

• Eating food or drinking water contaminated with tiny amounts of stool
• Close household or sexual contact with someone who has hepatitis A
• Travel to countries where hepatitis A is common
• Using drugs, whether injected or not
• Experiencing homelessness or unstable housing
• Men who have sex with men, and anyone with poor access to hand washing and sanitation

How it is checked

Because many infections cause similar symptoms, hepatitis A is confirmed with a blood test for a specific antibody called IgM anti-HAV, which appears early in the illness. Your doctor will also order liver function tests to see how inflamed the liver is and a clotting test to check how well the liver is working.

Doctors are required to report cases to the health department. Public health staff will ask about recent travel, food and contacts, and they may contact people you live with or have had close contact with so they can get vaccine or immune globulin in time. If you work with food, the health department will advise when you can return.

Related topics

• Hepatitis B and C: What the Evidence Actually Says (Liver Health)
• The Evidence on Liver Health, Without the Hype (Digestive Health)
• Returning Traveler Illness: What Published Guidance Supports (Travel Health)
• The Evidence on Adult Vaccination, Without the Hype (Preventive Care)

Where to go next

• The Short Guide to Hepatitis A
• Hepatitis A: Sorting the Evidence From the Noise
• Infectious Diseases: The Complete Guide
• The Evidence on Tuberculosis Basics, Without the Hype
• RSV (Respiratory Syncytial Virus): Sorting the Evidence From the Noise

When to get help

See your doctor for yellowing of the skin or eyes, dark urine, pale stools, loss of appetite or pain on the right side of the belly. Call 911 for confusion, extreme sleepiness, vomiting blood or easy bleeding or bruising, which can signal liver failure.

Where this comes from

• CDC — Hepatitis A Basics
• CDC — Hepatitis A Vaccination

How this page was put together

Every figure, recommendation and warning above is taken from the guidance named in Where this comes from. Nothing on this page is inferred, summarized or generalized beyond what those bodies publish: where they give a number, it is their number, and where they are silent, so are we. Pages are rebuilt whenever the underlying record changes. Sign-off by a named clinician, where it has happened, is shown at the top of the page along with the date.

Medical disclaimer

This article is general information, not medical advice. It cannot account for your own history, medication or circumstances. Always speak to your doctor, pharmacist or another qualified health professional before making changes that affect your treatment, and never delay seeking medical advice because of something you have read here. In an emergency, call 911.