VOL: 98, ISSUE: 23, PAGE NO: 50
Kim Gunn, RGN, MPH, is public health specialist (communicable disease and infection control), North Staffordshire Health Authority
Hepatitis A virus (HAV) is a positive-strand RNA virus classified as hepatovirus, a member of the Picornaviridae family. Following ingestion, the virus enters the bloodstream from unknown sites in the gastrointestinal tract. It then infects the liver cells, passing into the biliary tract to reach the intestine and appear in the faeces.
The incubation period for HAV may be 15-50 days, depending on exposure dose, but averages 28-30 days (Benenson, 1995). Clinical symptoms vary and can include asymptomatic infection, fever, anorexia, nausea, vomiting and sometimes jaundice, to acute icteric disease and fulminant hepatitis A. They are usually milder in children, and adults are at increased risk of developing jaundice or a more severe disease. The virus has not been reported to cause chronic infection (Battegay et al, 1995).
Diagnosis of acute HAV infection is routinely based on the detection of serum anti-HAV IgM antibodies, which are present at the onset of illness or at the peak of raised liver enzymes and may persist for several months after clinical recovery. IgM is replaced within weeks by immunoglobulin G (IgG). This indicates previous infection and is said to afford lifelong immunity. Salivary testing for HAV IgM is another validated method, which has been useful in identifying hepatitis A cases or susceptible individuals who may benefit from immunisation in outbreak situations (Thurston et al, 2000)
Surveillance of hepatitis A in England and Wales is based on statutory notifications and laboratory reports of positive anti-HAV IgM tests. The mild nature of the illness in some individuals may result in not consulting their doctor and consequently a notification not being submitted.
The main patterns of disease arise from sporadic cases, common-point source outbreaks - predominantly related to contaminated food or water - and community-wide outbreaks due mainly to person-to-person (faecal-oral) transmission (Benenson, 1995).
In infected individuals HAV is excreted in large amounts in faeces - 100 million infectious doses per gram (Mims et al, 1993). The virus can be detected in faeces 14-21 days before jaundice and until eight days after onset of jaundice, with the excretion of virus particles declining rapidly during the first seven days of illness. The individual is most infectious at the end of the incubation period until a few days after the onset of symptoms (Benenson, 1995).
Person-to-person transmission usually occurs by the faecal-oral route (and should not be confused with blood-borne transmission of hepatitis B and C); it can also be transmitted by contaminated water and food (Fig 1). Person-to-person transmission can lead to outbreaks in schools and care establishments. There is also increasing evidence that male homosexual contact can lead to sexual transmission. There is no such evidence for heterosexual contact (Brook, 1998). Many genitourinary medicine clinics see significant numbers of injecting drug users, and evidence suggests that this group is also at increased risk of hepatitis A (Shaw et al, 1999; Thurston et al, 2000).
Prevention of hepatitis A
The most important measures in the prevention of hepatitis A include:
- Good sanitation;
- Good water treatment and distribution systems;
- Good personal hygiene, with special emphasis on hand-washing;
- Safe disposal of faeces;
- Safe food preparation.
Education and training for all health care workers in the application of universal precautions and basic infection control procedures is an important element in the prevention and control of hepatitis A infection.
Hepatitis A vaccination (active immunisation) and/or immunoglobulin (passive immunisation) is recommended as pre-exposure prophylaxis for the following people:
- Susceptible travellers to areas of moderate or high HAV endemnicity;
- People with chronic liver disease or haemophilia;
- Laboratory workers working directly with the virus;
- Workers coming into contact with sewage;
- Homosexual men whose sexual behaviour is likely to put them at risk.
The majority of health care workers are not at an increased risk of hepatitis A and routine immunisation is not recommended (Salisbury and Begg, 1996).
The following high-risk groups were added to the ‘prevention by vaccination’ list in 2001:
- People with hepatitis B or C virus infection or liver cirrhosis of any cause;
- Injecting drug users;
Vaccination should be considered for individuals with special needs whose capacity to maintain good standards of hygiene is limited, and also for their carers, following risk assessment.
Several vaccines are now available using inactivated virus, grown in a cell-culture medium. These are thus free from risk of blood-borne diseases. Full immunity may take about two weeks to develop, and lasts for six to 12 months. A booster given six months later will extend immunity for 10 years.
Public health action
Following the notification of a case of hepatitis A the communicable disease control team (CDCT) and/or local authority environmental health officer (EHO) will:
- Contact the person or, in the case of a child, the parent/guardian and try to establish the source of infection;
- Gather surveillance information including history of diet, travel, household contacts and contact with other cases;
- Provide information and advice on enteric precautions and safe preparation and serving of food;
- Exclude persons in ‘risk groups’ 1 to 4 (Box 2) from work, school or nursery until seven days after the onset of jaundice and/or symptoms.
Microbiological clearance is not normally required. It is important to liaise with school health nurses and health visitors where children are in school or nursery settings so that good hygiene procedures can be reiterated and staff can be vigilant in identifying further cases.
Most people diagnosed with hepatitis A are cared for at home, and contact tracing will be undertaken by the GP in liaison with the CDCT. If hospital admission is necessary, contact tracing should be instigated by the clinical team, in liaison with the CDCT.
Contacts of a single isolated case are identified as family, sexual, household and other close contacts and offered prophylaxis. However, if it is restricted to this group the control of further spread of infection is ineffective. If given to a wider social group of recent household visitors - for instance, kissing contacts and those who have eaten food prepared by the index case - spread may be better controlled (Salisbury and Begg, 1996).
Whether in hospital or at home, careful attention should be paid to infection control practice in order to prevent further spread. Enteric precautions should be instigated until seven days after the onset of jaundice and/or symptoms. In outbreak situations routine contact tracing may be extended to target the at-risk population - for example, a particular school or intravenous drug-using population.
High-risk groups should be offered vaccination as a preventative measure. Vaccination and/or HNIG should also be used in the prevention of secondary infections in contacts of cases and in outbreak situations. The offer of HAV vaccine to prevent infection in travellers to countries of high risk for HAV should be encouraged. However, good personal hygiene remains the most important element in the prevention of HAV infection and spread. Health and social care workers and carers in domestic settings should be aware of good hygiene practice and have access to infection control advice. This can usually be obtained from the local CCDC, community infection control nurse and local authority environmental health department.