Epidemic Epidemiological Factors of Hepatitis C
3 , 2003
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
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
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.