Clinical Features
Hepatitis A
The disease presents with mild fever, jaundice, nausea, vomiting, poor appetite, tiredness, dark urine and pale stools following an incubation period of 2 - 6 weeks. Sometimes symptoms are so mild that the disease is not clinically apparent. Asymptomatic infection occurs frequently in children. Diagnosis is confirmed by blood tests of liver function and detection of antibodies to HAV in the circulation.
Hepatitis B
The average incubation period following infection is between 60 to 90 days. Initial symptoms include fever, joint pains, skin rashes, tiredness, decreased appetite and nausea, which are followed by jaundice, dark urine, and pale stools. Jaundice is not usually severe. The liver may be mildly enlarged on clinical examination. Some people (60-65%) may have a sub-clinical infection without jaundice and few other symptoms. They may be unaware that they have acquired hepatitis B infection.
Hepatitis B infection is diagnosed by the presence of a number of specific markers for the virus in the blood. These serological markers are used to determine the infectivity of the virus in the blood, and to monitor the progression of the infection.
Acute infection
20-25% develop acute hepatitis as described above following infection. Most people recover spontaneously without specific treatment including those with sub-clinical infection. The virus disappears from the blood within weeks or months.
However in 1% of acute infections a sudden severe fulminating hepatitis can develop leading to acute liver failure. This condition has a high mortality, and liver transplantation may be the only life saving treatment option.
Chronic infection
5-10% of people who are infected fail to clear the virus from the body within six months. They become long-term (chronic) carriers of hepatitis B and are diagnosed by specific viral markers in the blood. Many chronic carriers remain healthy and have no symptoms.
A small percentage of people develop chronic inflammation of the liver (chronic hepatitis), which progresses over a number of years to cirrhosis and hepato-cellular carcinoma. They also may remain relatively well for many years. Non-specific symptoms such as malaise may be reported and the liver is enlarged on clinical examination. The chronic infection may only be diagnosed when abnormal liver function is found on a routine blood test, or late manifestations of liver failure and cirrhosis appear.
Persistent and progressive inflammation of the liver leading to complications is more common in men (male: female 6 to 1), very young babies, the elderly, homosexual men, people with AIDS and people taking immuno-suppressive drugs.
Hepatitis C
Acute infection
The incubation period is variable - between 2 to 26 weeks with an average of 5 to 12 weeks. About 20% of people develop an initial illness with mild symptoms such as malaise, nausea and upper abdominal pain. Half of these will also have jaundice and dark urine.
Chronic infection
Up to 85% have no early symptoms following infection. In these people the infection persists and becomes long term (chronic). The chronic infection may only become apparent subsequently, when abnormal blood tests reveal persistent infection, or through the late development of symptomatic liver disease. Chronic infection is defined as persistence of the virus in the blood, as shown by blood tests, after 6 months. Many asymptomatic people will be unaware that they have the chronic infection, until they develop advanced liver damage some years later. They remain well with little or no ill health. They are described as chronic hepatitis C carriers, and may be a source of infection to others, for example, through use of contaminated needles and syringes.
The disease progression can be monitored with blood tests, but there is no good correlation between the degree of liver impairment and the symptoms such as fatigue experienced.
A small number of people clear the virus infection themselves spontaneously after the initial infection, and remain well.
20-30% of people with chronic infection develop cirrhosis within 15-30 years. For those with cirrhosis due to hepatitis C there is a 1-2% annual risk of developing hepatocellular carcinoma.
