Geographic pattern of tuberculosis in North Carolina

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NO. 33 North Carolina State Ubrary
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THE GEOGRAPHIC PATTERN OF TUBERCULOSIS IN NORTH CAROLINA
December 1984
by
Michael J. Patetta
I. INTRODUCTION
In 1918, there were 3,514 cases of tuberculosis (TB) in
North Carolina, which is a case rate of 139.34 per 100,000
population (1). There were also 3,412 deaths from TB for
a death rate of 135.30 (2). The case rate of TB has gone
down considerably, however, as in 1982 it was 13.5 per
100,000 population (3). Furthermore, only 63 people died
from TB in 1982 for a death rate of 1.05 per 100,000
population (4). Despite the decline in the number of
cases, TB is still a serious public health problem in North
Carolina. The state's case rate ranked 12th highest in the
U.S. in 1982 (5). What is even more perplexing, however,
is the preponderance of TB in eastern North Carolina.
The map in Figure 1 clearly shows this strong geographic
pattern of county morbidity rates for TB.
The major objectives of this paper are:
1) to summarizethe current morbidity and healthcare
delivery data on TB in North Carolina;
2) to provide indicators why an eastern band of coun-ties
has more than triple the TB morbidity rate of the
rest of the state;
3) to see if the counties with high TB rates have high
rates throughout the county or just in certain parts of
the county;
4) to expand the study area and see if Virginia and
South Carolina also have this eastern band of coun-ties
with a high incidence of TB.
II. BACKGROUND
The primary cause of TB is a bacterium called the
tubercle bacillus (mycobacterium tuberculosis).
Infection occurs through the inhalation of the organisms
present in the air or droplet nuclei expelled by the
coughing or sneezing of a person with active TB. The
measurable manifestation of infection is a positive
tuberculin skin test; however, signs and symptoms of TB
may be absent. Once infected, the person's immune
system usually proves adequate to limit the multiplica-tion
and spread of the bacilli. Around 5% of newly
infected individuals, though, do develop TB disease
within a year of their infection (6). If the bacilli produces
TB in the lung, then the disease is called pulmonary TB.
All other sites of TB are called extra-pulmonary TB.
Vague general symptoms such as fatigue, nervous
irritability, or anorexia usually signal the onset of pulmo-nary
TB (7). Later symptoms include a cough, a cold,
blood spitting, unexplained fever and night sweats, loss
of weight and swollen glands (8). The symptoms for
extra-pulmonary TB depend upon where the TB
develops.
Approximately 85% of the reported cases of TB in the
U.S. are pulmonary TB (9). It is much more a public
health problem than extra-pulmonary TB since it usually
is more contagious. In pulmonary TB, a cavity is fre-quently
formed in the lung and large numbers of viru-lent
bacilli are released from this cavity daily. Pulmonary
TB, however, is not a highly infectious disease when
compared to other diseases since transmission usually
requires close, frequent, or prolonged exposure (10).
Among persons infected with the tubercle bacillus,
only about 5-10% ever develop TB disease (11 ). However,
because the organisms remain viable within the body for
decades, the risk of disease is lifelong. The precise factors
that determine whether any infected individual will