Hepatitis viral

Basic facts

Acute hepatitis (typically presenting as acute jaundice) is generally caused by hepatitis A, B, C and E viruses, which belong to different virus families. These viruses also differ in their (a) modes of transmission, (b) geographical and epidemiological patterns, which explain various age-related incidence profiles, and (c) propensity to result or not in chronic infections. Hepatitis D (not detailed any further here) is a particular case, being caused by a defective virus that can replicate and cause disease only in individuals already co-infected or chronically infected with the hepatitis B virus.

Table 5.5 illustrates the main differences between the hepatitis viruses.

Table 5.5 Characteristics of the hepatitis viruses

Virus

Family

Transmission

Main groups at risk of infection

Complications

Hepatitis A

Picomaviridae

Faecal-oral

Non-immune travellers to regions where sanitation is problematic (in low endemicity areas) Young children, usually asymptomatic (in highendemicity areas)

Fulminant hepatitis

Hepatitis B

Hepadnaviridae

Parenteral + sexual

Injecting drugs users Contact with infected blood or blood products High-risk sexual behaviour

Fulminant hepatitis Chronic hepatitis, cirrhosis, liver cancer

Hepatitis C

Flaviviridae

Parenteral (+/- sexual)

Injection drugs users Contact with infected blood or blood products

Fulminant hepatitis Chronic hepatitis, cirrhosis, liver cancer

Hepatitis E

Currently unclassified

Faecal-oral

Large outbreaks in communities with inadequate water/waste water facilities Non-immune travellers to regions where HEV is endemic (very rare)

Fulminant hepatitis Mortality up to 20% in pregnancy

Cases of viral hepatitis are seen all over the world, occurring either sporadically or during epidemics of various magnitudes. Outbreaks of hepatitis A and hepatitis

E have been documented in refugee and internally displaced person camps (Chad,

Kenya, Kosovo, Namibia, Sudan).

This can be explained by the specific patterns of transmission of viral hepatitis.

✓ Hepatitis A virus transmitted by the faecal-oral route is already highly prevalent in countries with poor sanitary infrastructure. Under such circumstances, transmission generally occurs during childhood, at an age when most of the infections due to these viruses are mild or generally asymptomatic. This leaves the bulk of adult populations largely immune to new infections, and therefore protected against the most severe forms of the diseases typically seen at older ages. Hepatitis E has been found confined to geographical areas where faecal contamination of drinking-water is common. Most outbreaks have occurred following monsoon rains, heavy flooding, contamination of well water, or massive uptake of untreated sewage into city water-treatment plants. Further disruption of social and health infrastructures during emergencies in developing countries is expected at most to increase transmission of hepatitis A and E. Only when disasters hit populations previously enjoying good standards of sanitation, or countries with transition economies, is there a theoretically increased risk of outbreaks of hepatitis A or E.

✓ Transmission of hepatitis B and hepatitis C could potentially be of concern during emergencies under circumstances favouring the increased use of unsafe injection practices, illicit injecting drug use, unsafe sexual activities, or the use of unreliable blood transfusion facilities. Transmission of hepatitis among specific groups at risk under such circumstances is unlikely to be detected during the acute phase of an emergency, but should be taken into consideration in the planning of preventive activities and in the design of an integrated health surveillance system.

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