Hepatitis A Virus - HAV

Hepatitis A Virus - HAV

 

The targeted use of the Hepatitis A vaccine in the U.S. since 1995 has led to a dramatic decrease in the number of reported cases of Hepatitis A.

Epidemiology

  • Prevalence – >7000 cases per year in the U.S.;  50-70% of U.S. adults have antibodies

Organism

  • Nonenveloped RNA picornavirus
  • Infects only primates
  • Virus survives for extended periods in seawater, fresh water, waste water and soil
  • Resistant to freezing, detergents and acids
  • Lack of lipid envelope confers resistance to bile lysis
  • Virus infects the hepatocytes, no propensity for chronic infection

Risk Factors

  • Raw seafood
  • Infected food handlers
  • Day-care settings

Clinical Presentation

  • Occurs sporadically or in epidemics
    • More prevalent among day-care and school-aged children
    • Usually asymptomatic or mild (fever, nausea, malaise)
      • May cause fulminant liver failure in patients with immunosuppression or multiple comorbidities
    • No chronic state, but can cause fatal hepatic failure

Diagnosis

  • Laboratory testing
    • IgM antibodies to HAV generally appear 4 weeks after infection
      • May persist up to 4 months after onset of clinical symptoms
    • Total (IgM and IgG) antibodies indicate past infection or immunization; associated with immunity

Differential Diagnosis

  • Bacterial – leptospirosis, Q fever (Coxiella burnetii), Rocky Mountain spotted fever (Rickettsia rickettsii), secondary syphilis (Treponema palladium), sepsis, typhoid fever (Rickettsia typhus) 
  • Parasitic – liver trematodes, toxocariasis
  • Viral – cytomegalovirus (CMV), Epstein-Barr virus (EBV), hepatitis A, B, C, D or E, herpes simplex virus, varicella zoster virus
  • Reactions to drugs – acetaminophen, antiseizure medications, Isoniazid (Nydrazid), oral contraceptives, Rifampin (Rifadin), sulfonamides
  • Reactions to toxins – alcohol, tetrachloride
  • Autoimmune disease – autoimmune hepatitis, systemic lupus erythematosus (SLE)

Treatment

  • Supportive

Prevention

  • Vaccination prior to school entry

See Also