Hepatitis A virus hepatitis accounts for 20-25% of clinical hepatitis worldwide. It is due to is a non-enveloped positive stranded RNA picornavirus which is transmitted by the faecal-oral route (1). HAV hepatitis may be referred to as infectious hepatitis.
- usually self limiting
- fulminant hepatitis can occur rarely (<1%) (1)
- but rates are higher with increasing age and in those with underlying chronic liver disease, including those with chronic hepatitis B or C infection
- does not lead to chronic hepatitis (2)
- the virus is resistant to freezing, detergents and acids but inactivated in temperatures higher than 185°F (85°C) or by formalin and chlorine (3)
HAV infections acquired in the UK usually presents as:
- sporadic cases
- community-wide outbreaks - results from person to person transmission
- in developed countries person-to-person spread is the most common method of transmission
- point of source outbreaks - uncommon, related to contaminated food (2)
Hepatitis A infection can also be spread during sexual intercourse and through injecting drug use, and there have been a number of recent outbreaks among gay, bisexual and other men who have sex with men (GBMSM) and persons who inject drugs (PWID) in the UK (1)
The risk of acquiring HAV infection is higher in:
- travellers to developing countries
- men who have sex with men
- users of illicit drugs
- those with clotting factor disorders
- persons who handle nonhuman primates (5)
Peak excretion occurs during the 2 weeks before onset of jaundice (1)
- concentration of virus in the stools drops after jaundice appears but may persist for more than 40 days
- children may excrete the virus for longer than adults, although a chronic persistent state does not exist
Infection with HAV induces lifelong immunity (1).
Summary:
Reservoir:
- Human gastrointestinal tract
Epidemiology:
- Hepatitis A is no longer endemic in the UK and cases represent either importation following acquisition abroad or the importation of contaminated food. Frozen food or food components have been associated with outbreaks in mainland Europe, Ireland and the USA
- clusters, often in families or social groups, commonly occur around the primary case but onward transmission is otherwise uncommon
Transmission:
- Faeco-oral route
- transmission can also occur during sexual contact, particularly amongst MSM and through injecting drug use
- transmission within households is very common. Children <6 years are particularly effective transmitters, especially in schools
Incubation period:
- average = 28 days (Range 15-50)
Infectivity:
- two weeks before the onset of symptoms to one week after the onset of jaundice. Where jaundice is not reported, a history of dark urine or pale stools should be enquired about. If there are no symptoms of jaundice, onset of other symptoms (such as fatigue, nausea, and fever) should be used
- shedding may continue for many weeks but does not appear to be associated with transmission of infection
- a chronic carrier state is not known to follow acute infection
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