Hepatitis A

Rayner JL
Mind Map by , created about 4 years ago

A general overview of the disease.

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Rayner JL
Created by Rayner JL about 4 years ago
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Hepatitis A
1 ORIGIN
1.1 The causative organism
1.1.1 Hepatitis A virus (HAV) is the causative agent.
1.1.2 Hepatitis A is a viral liver disease that can cause mild to severe illness.
1.2 Incubation period.
1.2.1 The incubation period is fifteen to fifty days, with an average of 28–30 days.
1.3 Occurrence.
1.3.1 Hepatitis A occurs worldwide. In developing countries most people are infected during childhood.
1.3.2 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.
1.4 Period of communicability.
1.4.1 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.
1.5 Identification
1.5.1 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
2.1 Mode of Transmission.
2.1.1 Infection is transmitted by the faecal-oral route from person to person or via fomites.
2.1.2 Infectious food handlers may contaminate non-cooked foods such as salads.
2.1.3 Infection can occur through ingestion of contaminated food or water.
2.2 Natural reservoirs.
2.2.1 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
3.1 Signs and symptoms.
3.1.1 Fatigue
3.1.2 Fever
3.1.3 Nausea
3.1.4 Appetite loss
3.1.5 Hyperbilirubinemia induced jaundice - of the skin or sclera (eye whites.)
3.1.6 Bile in urine - dark amber colour
3.1.7 Light, or clay-coloured faeces
3.2 Mortality/Morbitiy
3.2.1 Epidemics can be explosive and cause significant economic loss.
3.2.2 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.
3.2.3 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.)
3.2.4 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
4.1 Methods.
4.1.1 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.
4.1.1.1 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.
4.1.2 Preventing faecal contamination and ensuring handwashing takes place is essential to controlling outbreaks.
4.2 Preventative measures.
4.2.1 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.
4.2.2 Improved sanitation and hygiene are the most effective ways to combat the disease behind vaccination.
4.2.3 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.
4.2.4 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.