Information on viral hepatitis is obtained through two
surveillance systems. Incidence data are collected from cases
reported to the CDC National Morbidity Reporting System by each
state
and territory. The number of cases, age of patient, and date
reported
of each type of hepatitis as classified by physician's diagnosis
appear in the Morbidity and Mortality Weekly Report (MMWR) and the
MMWR Annual Summary. Serologic and epidemiologic data pertaining
to
risk factors of disease acquisition are obtained from the Viral
Hepatitis Surveillance Program (VHSP), a totally separate voluntary
reporting system operated by the Hepatitis Branch, Division of
Viral
Diseases, Center for Infectious Diseases, Centers for Disease
Control.
Morbidity Trends Based on Cases Reported to the MMWR
Figure 1 shows the changes in incidence of reported cases of all
hepatitis since 1955 and by type since 1966. In 1984, the reported
incidence of hepatitis B surpassed that of hepatitis A for the
second
consecutive year. Of 57,557 cases of viral hepatitis reported to
the
MMWR in 1984, 38% were reported as hepatitis A; 45%, as hepatitis
B;
7%, as hepatitis non-A, non-B; and 10%, as unspecified hepatitis.
Virtually no change occurred in the reported incidence of hepatitis
A,
while there were slight increases in the reported incidence of
hepatitis B and hepatitis non-A, non-B. Combined with a decline in
the rate of unspecified hepatitis, these changes have resulted in a
nearly constant overall rate of viral hepatitis.
In 1984, states in the west and southwest regions continued to
report high rates of hepatitis A. Historically, the major
contributing factors to these high rates have been transmission of
hepatitis A in day care and sustained community-wide outbreaks due
to
person-to-person spread. Foodborne-associated outbreaks of
hepatitis
A often account for large year-to-year fluctuations in hepatitis A
rates. The states with the highest rates of hepatitis B are
clustered
primarily on the east and west coasts as in previous years. Non-A,
non-B hepatitis has been a separate reportable disease category in
the
MMWR since 1982. The low reported rates for this disease are
believed
to be due to incomplete serologic testing and underreporting.
Persons in the 20- to 29-year age group continue to have the
highest rates of both hepatitis A and hepatitis B. The risk of
acquiring hepatitis A appears to have declined in persons of all
age
groups except those less than 15 years of age. Some of this
decline
may be due to increased use of available serologic tests which may
have resulted in reclassification of the type of hepatitis
occurring
in older persons.
Although persons under 15 years of age still experience low
rates
of hepatitis B infection, the risk of acquiring this disease
continues
to increase for all other age groups. Persons in the 15- to
39-year
age groups tend to be in the high-risk categories (i.e., health
care
workers, parenteral drug abusers, and homosexual men) for acquiring
hepatitis B.
Viral Hepatitis Surveillance Program
Since 1980, the VHSP has received reports on approximately half
of
the cases reported to the MMWR. CDC's ability to accurately
analyze
and interpret nationwide trends and patterns, identify high-risk
groups, and determine mechanisms of transmission for each type of
hepatitis depends on (1) the local medical community's utilization
of
the appropriate serologic tests to distinguish between the
different
types of hepatitis and (2) the voluntary cooperation of the state
and
local health departments in completing and submitting the VHSP
forms.
Non-A, non-B hepatitis is now a separate reportable disease
category,
and since this type of viral hepatitis remains a diagnosis of
exclusion, serotesting is even more important. Differentiation of
any
of the types of viral hepatitis based on clinical or epidemiologic
characteristics alone is no longer acceptable since there is
considerable overlap between the different types of hepatitis with
respect to these characteristics.
The number of cases reported to the VHSP was 24,613 in 1984,
representing 43% of the cases reported to the MMWR in the same year
and down from 47% in 1983. Reporting of cases to the VHSP is not
consistent among states because, while many states reporting to the
MMWR also report to the VHSP, many of the states do not. The
percentage of agreement in reporting between the MMWR and the VHSP,
however, is not necessarily a measure of the actual completeness of
reporting from a particular state. Despite the difference in
numbers,
the cases reported to the VHSP are similar to those reported to the
MMWR with respect to the relative frequencies of the different
types
of hepatitis as well as the age distribution of the cases.
While serologic tests for diagnosing hepatitis B, including
hepatitis B surface antigen (HBsAg), have been available since the
early 1970's, a laboratory test for IgM antibody to hepatitis A
virus
(IgM anti-HAV) has only been available since 1981. The use of
these
two serologic tests to distinguish between the different types of
viral hepatitis has increased over the past 4 years. The tendency
for
physicians to use both tests has increased from 27% in 1981 to 64%
in
1984, while the frequency with which HBsAg is used as the only
serologic test has decreased from 43% to 19%.
Copies of the entire Hepatitis Surveillance Report Number 50
(issued
March 1986) are available from the Hepatitis Branch, Division of
Viral
Diseases, Center for Infectious Diseases, Centers for Disease
Control,
Atlanta, Georgia 30333, telephone number (404) 321-2342.
Disclaimer
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