Hepatitis A

Hepatitis A

1. ORIGIN

   • The causative organism
     • Hepatitis A virus (HAV) is the causative agent.
     • Hepatitis A is a viral liver disease that can cause mild to severe illness.
   • Incubation period.
     • The incubation period is fifteen to fifty days, with an average of 28–30 days.
   • Occurrence.
     • Hepatitis A occurs worldwide. In developing countries most people are infected during childhood.
     • It is highly endemic in some areas, particularly Central and South America, Africa, the Middle East, Asia, and the Western Pacific. There is no appreciable seasonal variation in hepatitis A incidence. All non immune people are susceptible to infection. Immunity after infection is probably lifelong.
   • Period of communicability.
     • Viral shedding persists for 1 to 3 weeks. Infected persons are most likely to transmit HAV 1 to 2 weeks before the onset of illness, when HAV concentration in stool is highest. The risk then decreases and is minimal the week after the onset of jaundice.
   • Identification
     • A blood test indicating IgM anti-HAV antibodies confirms recent infection. These antibodies are present for two to four months after infection. IgG antibodies alone are evidence of past infection.

2. MODE

   • Mode of Transmission.
     • Infection is transmitted by the faecal-oral route from person to person or via fomites.
     • Infectious food handlers may contaminate non-cooked foods such as salads.
     • Infection can occur through ingestion of contaminated food or water.
   • Natural reservoirs.
     • Humans are the only natural reservoir of the virus. There are no insect or animal vectors. A chronic HAV case has not been reported.

3. EFFECT

   • Signs and symptoms.
     • Fatigue
     • Fever
     • Nausea
     • Appetite loss
     • Hyperbilirubinemia induced jaundice - of the skin or sclera (eye whites.)
     • Bile in urine - dark amber colour
     • Light, or clay-coloured faeces
   • Mortality/Morbitiy
     • Epidemics can be explosive and cause significant economic loss.
     • Young children who are infected with hepatitis A typically have a milder form of the disease, usually lasting from 1–3 weeks, whereas adults tend to experience a much more severe form of the disease.
     • Hepatitis does not cause chronic infection and rarely causes death: Hepatitis A has a mortality rate of less than one percent (0.6) and over 70 percent of deaths occur in adults over the age of 49 (usually fulminant hepatitis.)
     • Hepatitis A occurs sporadically and in epidemics worldwide, with a tendency for cyclic recurrences. Hepatitis A viruses persist in the environment and can withstand food-production processes routinely used to inactivate and/or control bacterial pathogens.

4. CONTROL

   • Methods.
     • Vaccination programmes - two types of vaccines: one containing inactivated hepatitis A virus, and another containing a live but attenuated virus. There are both pediatric formulations, approved for persons 12 months through 18 years, and adult formulations approved for persons 19 years and older.
       • More than 95% of adults will develop protective antibody within 4 weeks of a single dose of either vaccine, and nearly 100% will seroconvert after receiving two doses. The vaccine protects against HAV in more than 95% of cases for longer than 25 years.
     • Preventing faecal contamination and ensuring handwashing takes place is essential to controlling outbreaks.
   • Preventative measures.
     • Groups at high risk of HAV infection as a result of behaviour, lifestyle or occupation should be the primary target of a hepatitis A vaccination programme.
     • Improved sanitation and hygiene are the most effective ways to combat the disease behind vaccination.
     • No specific treatment for hepatitis A is known. Sufferers are advised to rest, avoid fatty foods and alcohol (these may be poorly tolerated for some additional months during the recovery phase and cause minor relapses), eat a well-balanced diet, and stay hydrated.
     • Controlling risk factors: poor sanitation; lack of safe water; injecting drugs; living in a household with an infected person; being a sexual partner of someone with acute hepatitis A infection; and travelling to areas of high endemicity without being immunized.

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