Hepatitis A

What is hepatitis A?

Hepatitis A is a highly contagious liver infection caused by the hepatitis A virus (HAV).3 The hepatitis A virus replicates in the liver, transports through the bile, and is excreted into the feces via the biliary system.2

Hepatitis A can cause mild illness lasting a few weeks to a severe illness lasting several months.3

Mild
Severe
Range of Hepatitis A Symptoms From Mild (Lasting a Few Weeks), to Severe (Lasting Several Months)
Lasting a few weeks
Lasting several
months

Humans are the only natural host for the hepatitis A virus.2

What are the symptoms of hepatitis A?

The likelihood of symptomatic illness from the hepatitis A virus (HAV) is directly linked to age. Adults with HAV infection usually experience symptoms; however, hepatitis A in children under 6 years of age is largely asymptomatic. In fact, nearly 70% of children under 6 years of age with HAV infection show no symptoms.1

For those who experience symptoms, the onset is typically abrupt and includes:1

  • Fever
  • Fatigue
  • Loss of appetite
  • Nausea
  • Vomiting
  • Abdominal pain
  • Dark urine
  • Diarrhea
  • Clay-colored stool
  • Joint pain
  • Jaundice

How serious is hepatitis A?

People who get hepatitis A may feel sick for a few weeks to several months but usually recover completely and do not have lasting liver damage. In rare cases, hepatitis A can cause liver failure and even death; this is more common in older people and in people with other serious health issues, such as chronic liver disease.3

How is hepatitis A transmitted?

The transmission of the hepatitis A virus infection occurs from person-to-person contact through the fecal-oral route or by consuming contaminated food or drink.2

Can hepatitis A be transmitted if someone has no symptoms?

Yes. Most children under the age of 6 who have been infected display no symptoms of hepatitis A but could spread the virus. A person can also spread the virus up to 2 weeks before symptoms appear.3

How long do the symptoms of HAV infection last for those who display symptoms?

Usually, symptoms do not last longer than 2 months; however, 10% to 15% of people with HAV experience prolonged or relapsing symptoms for up to 6 months.2

What is the incubation period for hepatitis A?

The average incubation period for hepatitis A is approximately 28 days (range: 15–50 days).2

Can HAV survive outside the body? How can the hepatitis A virus be killed?

Depending upon environmental conditions, HAV can live outside the body for months. Heating food at temperatures >185° F (>85° C) for 1 minute or disinfecting surfaces with chlorine can inactivate HAV; however, the virus is still capable of being spread if food contamination occurs after cooking.1

Waterborne outbreaks of HAV in developed countries are rare; occurrences of this nature have been generally attributed to sewage contamination and inadequately treated water.2

How is hepatitis A diagnosed?

A hepatitis A diagnosis is made through an evaluation of symptoms and certain blood tests (eg, serology or nucleic acid amplification tests).1

How prevalent is hepatitis A?

Hepatitis A incidence increased 1,325% from 2015 through 2019. In 2019, a total of 18,846 cases of hepatitis A were reported to the CDC from all 50 states and the District of Columbia. The overall incidence rate in 2019 was 5.7 reported cases per 100,000 population. After adjusting for under-ascertainment and under-reporting, an estimated 37,700 hepatitis A cases (95% bootstrap confidence interval=26,400–41,500) occurred in 2019.4

What are some of the risk factors for hepatitis A infection?

The CDC has identified people at high risk for acquiring and/or developing complications from hepatitis A1,2

At increased risk for acquiring hepatitis A infection:

  • Men who have sex with other men
  • People who use injection or non-injection drugs
  • International exposure – travel to countries where hepatitis A is common, or have close personal contact with anybody from a high-risk region, such as an international adoptee
  • Work environments – working with material containing hepatitis A in a research laboratory setting
  • People experiencing homelessness
  • Local outbreaks – living in a region where there is an outbreak and have one or more other risk factors

At increased risk for severe disease from hepatitis A infection:

  • People with chronic liver disease
  • People with human immunodeficiency virus (HIV)

Does recovery from hepatitis A infection lead to lifelong immunity?

Yes, once a person has recovered from HAV infection, anti-HAV IgG antibodies remain in the person’s blood. This provides lifelong protection against HAV disease.1,2

How is hepatitis A treated?

There is no specific treatment for hepatitis A virus infection. Treatment and management of HAV infection are supportive.2

For more information, please visit Centers for Disease Control and Prevention (CDC):

CDC Disease Information

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CDC=Centers for Disease Control and Prevention; HAV=hepatitis A virus; HIV=human immunodeficiency virus; IgG=immunoglobulin G.

ref1

Reference

  1. Centers for Disease Control and Prevention (CDC). Hepatitis A questions and answers for health professionals. https://www.cdc.gov/hepatitis/hav/havfaq.htm. Updated July 28, 2020. Accessed April 1, 2021.
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Merck does not review or control the content at the site to which this link connects. Merck makes no representation with respect to the content of any non-Merck site.

ref2

Reference

  1. Centers for Disease Control and Prevention. Epidemiology and Prevention of Vaccine-Preventable Diseases. In: Hall E, Wodi AP, Hamborsky J, et al, eds. 14th ed. Washington, D.C. Public Health Foundation, 2021: 125–142. https://www.cdc.gov/vaccines/pubs/pinkbook/hepa.html. Accessed September 20, 2021.
ref3

Reference

  1. Centers for Disease Control and Prevention (CDC). Hepatitis A questions and answers for the public. https://www.cdc.gov/hepatitis/hav/afaq.htm. Updated July 28, 2020. Accessed May 7, 2021.
ref4

Reference

  1. Centers for Disease Control and Prevention. Viral hepatitis surveillance report – United States, 2019. https://www.cdc.gov/hepatitis/statistics/2019surveillance/index.htm. Published May 2021. Accessed July 9, 2021.
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US-VAQ-00728 10/21