The Epidemic - Epidemiological Factors

Hepatitis C was only discovered in 1989, and since that time, studies of infected populations have grown in frequency and sophistication. Early assessments of the total numbers of infected individuals and rates of infection were greatly underestimated, and have been rapidly revised upwards. There is reason to believe that this trend will continue, and that current numbers are probably greatly underestimated. A number of factors must be taken into consideration when assessing the true extent and spread of hepatitis C.

1. The disease is not generally recognized by the public, so levels of concern and testing are low.

2. The medical community is not well educated about this disease, so many, many cases go unrecognized and untreated. Because of this same lack of knowledge, a majority of doctors do not recommend testing for hepatitis C to their patients, even if they are in high risk groups.

3. In most cases, the disease is asymptomatic for years, even decades, before progressing to chronic liver disease. Because the largest numbers of people infected with the disease are believed to have been infected within the past 15-20 years, the true burden of infection may not become apparent for many years to come.

4. Studies are almost always several years old before they are published - the data they are based upon

sometimes even older - so published statistics are usually lower than current data would indicate.

5. Sample populations used in studies are frequently not representative of high-risk groups. For example, studies of suburban populations, or studies involving blood donors, frequently miss large parts of the at-risk population, which might tend to be concentrated in cities or not regularly donate blood.

6. The virus mutates frequently, resulting in strains of the virus which are undetectable by current assays. While researchers are always developing newer assays to detect new strains, they are inevitably a little behind. Some hepatologists (liver specialists) believe that the hepatitis C virus is in many cases able to elude detection by current means.

7. Because of its frequent mutation and diverse genotypes, the use of different assays in different epidemiological studies has led to a great deal of discrepancy in methods and probable accuracy. Comparisons between these studies is thus risky and often inaccurate.

8. More than 40% of currently recognized infected individuals contracted the disease through means unknown to them (although it is believed that most of these cases have identified risk factors associated with them - approximately 10% of cases have genuinely unknown means of transmission). This means that many

of the people who are infected may not even be aware that they are at risk for this disease. Moreover, the existence of unknown means of transmission suggests that epidemiological studies based on current theories about transmission may not be representative.

9. Less developed nations, particularly in the Third World, have little or no public education about the disease and have made few attempts to curtail the spread of the disease, so statistics from these regions are frequently flawed (and estimates often low).

10. There is a great deal of political and social controversy concerning this disease, which has and will continue to result in inaccurate reporting or underreporting of rates of infection, by individuals, physicians, and public health agencies in this country and around the world.

Because of these factors, the number of documented cases of hepatitis C have represented only a tiny fraction of the total number of individuals actually believed to be infected - and estimates of total infected populations are likely to be low in relationship to actual rates of infection. These issues should not lead to the belief that accurate estimates cannot be made, but rather should make clear that recent and future figures of the incidence of the disease in the United States and the world will likely be lower than the true incidence for some time to come.