WHO-recommended surveillance standard of acute viral hepatitis
Rationale for surveillance
Several distinct infections are grouped as viral hepatitis. Transmission is mainly through the oral-faecal route for hepatitis A and E, and percutaneous exposure to body fluids, including sexual intercourse, for hepatitis B, C and D. The course of the disease may be fulminating (e.g. hepatitis E in pregnancy); chronic infection and severe sequelae occur mainly in hepatitis B, C and D
Control measures for blood-related transmission include ensuring transfusion safety, injection safety and (for hepatitis A and hepatitis B at least) immunization. Hepatitis B is targeted by WHO for reduced incidence/prevalence
Recommended case definition
Clinical description
An acute illness typically including acute jaundice, dark urine, anorexia, malaise, extreme fatigue and right upper quadrant tenderness. Biological signs include increased urine urobilonogen and >2.5 times the upper limit of serum alanine aminotransferase
Note: Most infections occur during early childhood. A variable proportion of adult infections are asymptomatic
Laboratory criteria for diagnosis
Hepatitis A: positive for IgM anti-HAV
Hepatitis B: positive for IgM anti-HBc or (less desirably) hepatitis B surface antigen (HBsAg)
Non-A, non-B: negative for IgM anti-HAV and IgM anti-HBc or (less desirably) HBsAg
Note: The anti-HBc IgM test, specific for acute infection, is not available in most countries. HBsAg is often available but is less desirable since it cannot distinguish acute new infections from exacerbation of chronic hepatitis B. Nevertheless, continued HBsAg seropositivity (> six months) is an indicator of chronic infection. For patients with non-A, non-B, the following testing is used for a diagnosis of acute hepatitis C, D or E
Hepatitis C: positive for anti-HCV
Hepatitis D: positive for IgM anti-HBc or (less desirably) HBsAg plus anti-HDV positive (N.B. only occurs as co-infection or superinfection of hepatitis B)
Hepatitis E: positive for IgM anti-HEV
Case classification
Suspected: A case that is compatible with the clinical description
Probable: Not applicable
Confirmed: A suspected case that is laboratory-confirmed or, for hepatitis A only, a case compatible with the clinical description in a person who has an epidemiological link (i.e. household or sexual contact with an infected person during the 15-50 days before the onset of symptoms) with a laboratory-confirmed case of hepatitis A
Recommended types of surveillance
- Routine monthly reporting of aggregated data on suspected cases, and, if available, the number of confirmed cases of each type of hepatitis should be reported from the peripheral level to the intermediate and central levels
- Designated reporting sites at all levels should report at a specified frequency (e.g. weekly or monthly) even if there are zero cases (often referred to as "zero reporting")
- All outbreaks should be investigated immediately and confirmed serologically
Recommended minimum data elements
Aggregated data
- Number of third doses of hepatitis B vaccine (HepB3) administered to infants
- Number of suspect cases
- If available, number of confirmed cases for each type of hepatitis
Recommended data analyses, presentations, reports
(from multiple sources of data in addition to surveillance data):
- HepB3 coverage in infants by year and geographical area
- Number of acute viral hepatitis cases and incidence rate by year, month, geographical area and (if data exist) age group
- Where data exist on etiological agent, incidence rate of each type of acute viral hepatitis by geographical area, year, month and age group
- Proportion of all cases of chronic liver disease, cirrhosis and primary liver cancer that are HBsAg-positive or anti-HCV-positive (see special aspects section)
Principal uses of data for decision-making
- Monitor HepB3 coverage by geographical area to measure areas with weak performance and take action
- Investigate all suspected/reported outbreaks
- Determine the specific cause of acute viral hepatitis cases (reported routinely or during outbreaks) so that corrective measures can be taken
- Understand the epidemiology of hepatitis by etiological agent in terms of distribution over time, by age group and geographical area
- Measure the incidence (including age-specific incidence) and prevalence of HBsAg and anti-HCV
- Measure the proportion of cases of acute viral hepatitis, chronic liver disease, cirrhosis and primary liver cancer that are hepatitis B virus or hepatitis C virus carriers to:
1) determine the burden of the disease in the population
2) prioritize it among other diseases of public health importance
3) choose the proper strategies for its control
Special aspects
Surveillance data on acute viral hepatitis from developing countries should be interpreted with caution. Differentiation of types of viral hepatitis (A to E) based on clinical diagnosis is unreliable and serological testing is necessary for accurate diagnosis. Unfortunately, many developing countries do not have access to diagnostic reagents. Most infections with hepatitis A, B, C and E virus occur asymptomatically (in developing countries usually among children) and are not detected and reported to the surveillance system. Therefore, a low incidence of acute viral hepatitis should not be misinterpreted as a low prevalence of viral hepatitis infection
Understanding the epidemiology and burden of disease of viral hepatitis requires an understanding of the sequelae of hepatitis B, C and D infection. These include asymptomatic chronic infection, chronic hepatitis, cirrhosis and primary liver cancer. Measuring the burden of these conditions requires data collection from sources not traditionally used by infectious disease epidemiologists, including data on hospital discharge and mortality (for chronic hepatitis, cirrhosis and liver cancer) and data from cancer registries. Special seroprevalence surveys may be needed to measure the prevalence of hepatitis B and hepatitis C infection in the general population and in special groups such as blood donors, pregnant women, military recruits, health care workers, certain patient groups (e.g. patients with liver disease, people on dialysis, hemophiliacs) and ethnic subpopulations
The assessment of coverage of hepatitis B vaccine is similar to that of other vaccines used for routine immunization. Vaccine is given to infants (and in some industrialized countries to adolescents) prmarily to prevent the development of chronic liver disease and liver cancer. Serological testing for documenting seroconversion in children is usually unnecessary: numerous studies have shown that the vaccine is 85% to 100% effective in preventing chronic infection