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Tuberculosis Genotyping Network, United States
The Continued Threat of Tuberculosis
Thomas R. Navin, Scott J.N. McNabb, and Jack T. Crawford
*Centers for Disease Control and Prevention, Atlanta, Georgia, USA
Suggested citation for this article: Navin TR,
McNabb SJN, Crawford JT. The continued threat of tuberculosis. Emerg
Infect Dis [serial online] 2002 Nov [date cited];8. Available
from URL: http://www.cdc.gov/ncidod/EID/vol8no11/02-0468.
Why would a journal that tracks and analyzes emerging infectious disease
trends devote an entire issue to tuberculosis, a disease that emerged
some 15,000 to 35,000 years ago (1,2)? The disturbing
answer is that tuberculosis is reappearing in many countries as a public
health crisis. Thus, if not an emerging disease, it is an important reemerging
disease, and though ancient, it is not a disease of the past. A staggering
1.9 million around the globe die of tuberculosis each year—another 1.9
billion are infected with Mycobacterium tuberculosis and are at
risk for active disease (3).
In the 20th century, the United States made impressive strides in tuberculosis
control. From the early 1900s, when some areas began systematic reporting
of death rates, tuberculosis rates steadily declined from approximately
200 deaths per 100,000 per year to less than 1 death per 100,000 in 1985.
In 1953, a national surveillance system was established for reporting
new cases of tuberculosis disease; that year, reported annual incidence
was 53 cases per 100,000 population (4). From 1953 to
1984, tuberculosis disease incidence dropped steadily at an average rate
of 5.8% per year to 9.4 cases per 100,000.
In 1985, however, the United States saw a reversal in this long-standing
downward trend, and tuberculosis reemerged as a public health threat.
From 1985 to 1992, not only did the number of cases increase from 22,201
to 26,673, but also large outbreaks were reported. Many of these, especially
in hospitals and other health-care settings in large cities (5),
were caused by multidrug-resistant M. tuberculosis. Several factors
contributed to this increase, including the emergence of the HIV epidemic
and large influxes of immigrants from countries in which tuberculosis
was common. Perhaps the major reason for the reemergence, however, was
the end in 1972 of categorical federal funding for control activities
and the subsequent deterioration of public health infrastructure for tuberculosis
control.
In response to the crisis of reemerging tuberculosis, categorical grants
were restored and federal funding was increased. The funding, modest at
first, rose sharply in 1992 and again in 1993 and 1994. The Centers for
Disease Control and Prevention (CDC) transfers most of its appropriated
funds to tuberculosis control programs in states and large cities. These
funds support clinics and laboratories, administer directly observed therapy,
intensify investigation of latent infection in persons at high risk for
active disease, sponsor clinical and epidemiologic research, and expand
surveillance to monitor the impact of these efforts. Renewed investments
paid off, and after a peak in 1992, tuberculosis incidence in the United
States has declined each year. From 1992 to 2001, the annual decline averaged
7.3%, even greater than before 1985. But future success is not guaranteed.
The National Academy of Sciences Institute of Medicine, in its 2000 report
on tuberculosis control efforts in the United States, warned against the
“complacency and neglect” that come with declining numbers of cases and
reaffirmed the goal of TB elimination (annual incidence of <1 case
per 1,000,000 population) in the United States (6).
In 2001, the 15,989 tuberculosis cases reported to CDC represented only
a 2% decline from 2000, the smallest decline in 9 years. Although data
from a single year do not constitute a trend, these numbers may be the
first sign of stagnation in our control efforts. The proportion of cases
in persons born outside the United States is growing; in 2001, that figure
reached 50%. Efforts to reduce tuberculosis transmission in the United
States have little effect on reducing risk for those infected elsewhere.
The proportion of cases in persons born in other countries will probably
continue to rise, unless domestic programs providing tuberculosis services
for immigrants are strengthened and international programs are expanded.
Another risk, in the current climate of bioterrorism, is the possible
intentional spread of multidrug-resistant M. tuberculosis. This
risk requires new tools for detection and rapid and effective response.
Currently strengthened surveillance systems closely monitor changes in
disease epidemiology. If tuberculosis elimination progress in the United
States slows, we are prepared to respond quickly.
References
- Kapur V, Whittam TS, Musser JM. Is
Mycobacterium tuberculosis 15,000 years old? J Infect Dis
1994;170:1348–9.
- Hughes AL, Friedman R, Murray M. Genome-Wide Pattern of Synonymous
Nucleotide Substitution in Two Complete Genomes of Mycobacterium tuberculosis.
Emerg Infect Dis 2002;8. (this issue).
- Dye C, Scheele S, Dolin P, Pathania V, Raviglione MC, for the WHO
Global Surveillance and Monitoring Project. Global
burden of tuberculosis: estimated incidence, prevalence, and mortality
by country. JAMA 1999;282:677–86.
- Centers for Disease Control and Prevention. Reported tuberculosis
in the United States, 2001. Atlanta: U.S. Department of Health and Human
Services, Centers for Disease Control and Prevention, September 2002.
- Cantwell MF, Snider DE, Cauthen GM, Onorato IM. Epidemiology
of tuberculosis in the United States, 1985 through 1992. JAMA 1994;272:535–9.
- Institute of Medicine. Ending neglect: the elimination of tuberculosis
in the United States. Washington (DC): National Academy Press, 2000.
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