Hepatitis A

What is it?

Hepatitis A is an infection caused by the hepatitis A virus (HAV). HAV belongs to the family Picornaviridae, genus Hepatovirus. It replicates primarily in liver cells and is one of the most common causes of acute hepatitis (inflammation of the liver) worldwide.

Unlike infection with hepatitis B and C viruses, HAV infection does not usually cause chronic liver disease.

What to look for

The incubation period for hepatitis A infection is 15 to 50 days. Infected children generally experience either no symptoms or mild symptoms only. Approximately 70% of infected adults will be symptomatic. Symptoms of infection fit into two distinct phases, a prodromal (pre-icteric) phase and an ictreric (jaundice) phase. Prodromal phase features include general malaise and exhaustion, fever, nausea and lack of appetite and abdominal pain. Icteric phase features include pruritus (itchy skin), dark urine, pale stools and yellowing of the eyes and skin.

The duration of symptoms can vary, lasting only a few weeks or as long as 6 months. Liver function tests can take 1 to 2 months to normalise after the onset of infection. In rare cases, infection can result in fulminant hepatitis (acute liver failure), which may be fatal without liver transplant.

Hepatitis A mortality rates increase with age and can be associated with the presence of underlying medical risk factors. Up to 10% of cases will relapse; all relapsed cases will recover.

Rarely, hepatitis A can also lead to pancreatitis, rash, nephritis (kidney inflammation) or glomerulonephritis (inflammation of the glomeruli, small blood vessels in the kidney), pneumonitis (lung tissue inflammation), pericarditis (inflammation of the lining of the heart muscle), haemolysis (the destruction of red blood cells), and acute cholecystitis (gallbladder inflammation). Guillain–Barré syndrome, encephalitis (brain inflammation) and central myelitis (spinal cord inflammation) have also been reported.

How is it transmitted?

Hepatitis A is highly infectious. Cases are considered infectious from two weeks prior to the onset of prodromal phase up until either one week after the onset of jaundice (if present) or two weeks after the onset of the prodromal phase (if there is no jaundice). People with asymptomatic infections can still transmit disease.

Transmission occurs through the faecal–oral route, close person-to-person contact, contaminated food and water, and via fomites (e.g. fabric and other surfaces contaminated by faeces). Common sources include:

• eating contaminated raw, frozen or undercooked food
• drinking contaminated water
• touching dirty nappies, linen or towels of a person with hepatitis A
• sharing personal items such as toothbrushes
• being in direct contact (including sexual) with a person with hepatitis A.

HAV can survive in the environment, persisting on unwashed hands for several hours and at least one month at room temperature on surfaces. It can withstand food production processes (heat and freezing) commonly used to inactivate pathogens.

Epidemiology 

The World Health Organization (WHO) estimates that, globally, approximately 1.5 million are infected with HAV people each year. Transmission and infection are more common in low- and middle-income countries with poor sanitation.

In Australia rates of HAV infection are low, with most cases linked to travel to endemic countries or outbreaks relating to contaminated food.

Aboriginal and Torres Strait Islander children are at greater risk of infection than non-Indigenous children. The higher risk of infections stem from factors such as overcrowding and poor sanitation. Following the introduction of the National Immunisation Program (NIP)-funded hepatitis A vaccination for First Nations children in the Northern Territory, Queensland, South Australia and Western Australia, rates of infection and hospitalisations in this population have declined considerably.

Prevention 

Hepatitis A risk can be mitigated though measures such as improved sanitation (water supply and sewerage) and food handling practices (handwashing practice before food preparation, before meals and after toileting).

It is likely that previous infection provides lifelong protection against hepatitis A.

Vaccination is highly effective in preventing infection.

Vaccination 

Vaccination against HAV is available through either monovalent or combination vaccines (combined with hepatitis B ). Vaccines are administered intramuscularly (IM).

Vaccination is funded on the NIP for Aboriginal and Torres Strait Islander children living in the Northern Territory, Queensland, South Australia and Western Australia in a 2-dose schedule given at 18 months and 4 years of age.

Other populations at high risk of infection (e.g. those with pre-existing liver disease or other medical risk factors, people traveling to endemic countries, those with occupational exposure risk) may also be recommended vaccination, which is not funded. Refer to the Australian Immunisation Handbook: Hepatitis A – Recommendations for a full list of these recommendations.

Table 1: Hepatitis A vaccine brands available in Australia