Hepatitis A

List of contents:

• Transmission
• Pathophysiology
• Clinical manifestations
• Laboratory findings
• Extrahepatic manifestations
• Complications
• Diagnosis
• Treatment
• Vaccination and prevention

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Transmission- 

Person-to-person contact

Transmission within households

Sexual transmission

Residential institution transmission

Daycare center transmission

Transmission among military personnel

Contact with contaminated food or water

Consumption of raw or undercooked shellfish, vegetables, or other foods

Consumption of foods contaminated by infected food handlers

Blood transfusion

Illicit drug use

Pathophysiology-

• Cytotoxic cell injury, mediated by host immune system against infected Hepatocytes.
• Interferon-gamma appears to have a central role in promoting clearance of infected hepatocytes

Clinical manifestations-

• Usually self-limited illness.
• Symptoms- nausea, vomiting, abdominal pain, jaundice.
• Incubation period- 15 to 50 days

Laboratory findings-

• Elevated enzymes (often >1000 IU/dL). (ALT>AST)
• Elevated bilirubin.
• Elevated ALP.
• Recovery from acute infection and normalization of lab values usually happen in 3 to 6 months.

Fulminant hepatic failure –> encephalopathy + INR >/= 1.5 + acute liver injury.

• Usually rare in acute HAV infection.
  • Can occur in individuals with age >50 years, with other comorbidities like HBV or HCV.

Extrahepatic manifestations-

• Rash
• Arthralgia
• Glomerulonephritis
• Vasculitis

Complications-

1. Cholestatic hepatitis- 
   1. jaundice >3 months, with pruritis, fever, weight loss, diarrhea, malaise.
   1. Self-resolving with no sequelae.
   1. Treatment is only supportive. Cholestyramine can be given for pruritis.
2. Relapsing hepatitis-
   1. Relapse of symptoms during 6 months of acute infection.
   1. The duration of clinical relapse is generally less than three weeks, although biochemical relapse may last as long as 12 months.
   1. Self-resolving, treatment is supportive.
3. Autoimmune hepatitis-
   1. Rarely, Acute HAV infection, can be a trigger for autoimmune hepatitis.

Diagnosis-

• IgM antibodies for HAV.
• These are detectable at time of symptom onset and up to 3-6 months after infection.
• IgG antibodies are detectable in convalescence period and usually last for decades, and provides lifelong immunity.

Differential diagnosis

Treatment-

• Supportive.
• Medications causing liver injury should not be used.
• Full clinical and biochemical recovery usually occurs within 3 to 6 months.
• Patients with fulminant hepatic failure require aggressive supportive therapy and may require liver transplantation.

Prevention-

• Indications-
  • Children 12 to 23 months.
  • children and adolescents 2 to 18 years who were previously not vaccinated.
  • Infants 6 to 11 months who are travelling to countries which have endemic HAV infections. the travel-related dose should not be counted toward the routine two-dose series.
  • At risk adult populations- MSM’s, Chronic liver disease, HBV or HCV infected individuals, HIV infection, Injection drug users, homeless individuals.

Individuals who do not need routine vaccination against hepatitis A include:

• Food service workers (in the absence of an outbreak)
• Individuals who receive blood products for clotting disorders (eg, haemophilia) 

Post exposure prevention-

Indications-

• Exposure to HAV infected individuals. (household contacts, sexual contacts)
• Individuals who have shared illicit drugs
• Food handlers- if a food handler is tested positive, then other food handlers should be given post exposure protection.
• Postexposure prophylaxis is not warranted in association with a single case of hepatitis A in a school, office, or hospital if the source of infection is outside the school or work setting.

Vaccines-

• HAVRIX – inactivated HAV vaccine.
• BioVac-A – live attenuated HAV vaccine.

Doses- 2 doses, at least 6-12 months apart.

Passive immunity-

• Immunoglobulin is given along with HAV vaccine in individuals with acute HAV infection or contact to HAV infected person if-
  • Age >40 years.
  • Age >12 months, and are immunocompromised or have chronic liver disease.
  • Age <12 months and HAV vaccine is contraindicated (allergic reactions etc,.)
  • Infants < 6months (HAV vaccine cannot be given)
  • Dose- 0.1ml/kg I.M

References- 

1. Centers for Disease Control and Prevention. Hepatitis A Questions and Answers for Health Professionals. http://www.cdc.gov/hepatitis/hav/havfaq.htm#vaccine (Accessed on October 05, 2016).
2. Centers for Disease Control and Prevention. Health Information for International Travel 2020: The Yellow Book. https://wwwnc.cdc.gov/travel/page/yellowbook-home (Accessed on July 30, 2019).
3. World Health Organization. Hepatitis A. http://www.who.int/mediacentre/factsheets/fs328/en/ (Accessed on February 17, 2017).
4. HAVRIX IM injection, hepatitis A vaccine IM injection. GlaxoSmithKline, Research Triangle Park, NC 2011.

For further reading visit American society of gastroenterology.