TB Today

The Changing Epidemiology of TB
Populations Most Affected by TB
Challenges to TB Elimination

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The Changing Epidemiology of TB

Tuberculosis (TB), a disease caused by bacteria called mycobacterium tuberculosis, causes nearly 2 million deaths worldwide each year.¹

Between 1985 and 1992, cases of TB in the United States increased by 20 percent. This period of resurgence of TB disease was fueled by:

• The onset of the HIV epidemic
• Increases in TB cases among foreign-born persons
• Outbreaks in congregate settings (correctional facilities and homeless shelters)
• Deterioration of the infrastructure for TB services
• Development of difficult-to-treat cases of Multiple Drug Resistant (MDR) TB²

Today the trend has been reversed. TB cases reported to CDC for 2005 represented a 2.9% decrease from 2004 and a 47% decrease from 1992,³ when the number of cases and the case rate peaked during a resurgence in the United States. In 2005, the thirteenth consecutive year of decline, the TB case rate was 4.8 per 100,000.⁴ This reduction is attributed to more effective TB-control programs that emphasize prompt identification of persons with TB, prompt initiation of appropriate therapy, and efforts to ensure that therapy will be completed.

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Populations Most Affected by TB

The recent success in TB control in the United States is tempered by the burden of TB among foreign-born persons residing in this country. The case rate among foreign-born persons is now at least eight times higher than among U.S.-born persons.⁵

In 1991, 73 percent of reported TB cases were among U.S.-born persons (8.2 cases per 100,000) while 27 percent were in foreign-born persons (33.9 per 100,000). In comparison, 55 percent of TB cases in 2005 occurred in the foreign born.⁶ From 2001 through 2005, the top five countries of origin of foreign-born persons with TB were Mexico, the Philippines, Vietnam, India, and China.⁷

In 2005 in the United States, non-Hispanic Asians had the highest TB rate, 25.8 per 100,000, which was down from 29.6 in 2003; non-Hispanic native Hawaiians and other Pacific Islanders had the second-highest TB case rate (13.8), down from 16.4 in 2003. TB rates declined at least 50% from 1993 through 2005 in the other racial/ethnic groups: among non-Hispanic whites from 3.6 to 1.3, among non-Hispanic blacks from 28.5 to 10.9, among Hispanics from 19.9 to 9.5, and among non-Hispanic American Indians and Alaska Natives from 13.9 to 6.9.⁸

Learn more about Communities at Risk.

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Challenges to TB Elimination

The decrease in TB incidence to historic low levels creates challenges for public health officials who are working to sustain programs and systems. TB elimination is threatened, however, by several converging factors, including the:

• Retreat of TB into high-risk populations at the margins of society where it can resist detection
• Persistence and growth of the global TB epidemic
• Limitations of current control measures and recognition of the need for new tests and treatments, plus an improved vaccine
• Changes in the health care system that make the current context for TB elimination very different from that of a decade ago

Distinctive challenges to TB control have arisen in regions where cases occur infrequently. Tuberculosis outbreaks have occurred in such areas and have produced severe and long-term effects. Low-incidence states or local jurisdictions with minimal TB control programs sometimes are unprepared to detect and contain these outbreaks.

Likewise, shifting migration patterns are rapidly altering the TB epidemiology in communities and states that previously had not had large immigrant populations who are at risk for TB. In this scenario, existing TB control programs that are equipped only for infrequent cases are confronted with an abrupt increase of cases and unfamiliar cultural issues. In addition, because of the rarity of TB, some healthcare providers in these settings lack either proficiency in TB diagnosis or familiarity with the latest treatment guidelines.⁹

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What Is Being Done?

Learn more about TB elimination and control today.

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¹ World Health Organization (WHO) 2006 Tuberculosis Facts (PDF)
² Cantwell MF, Snider DE, Cauthen GM, Onorato IM. Epidemiology of tuberculosis in the United States, 1985 through 1992. JAMA 1994;272:535-9. sited in CDC. Tuberculosis elimination revisited: Obstacles, opportunities, and a renewed commitment. Advisory Council for the Elimination of Tuberculosis (ACET). MMWR 1999;48(No. RR-9).
³ Reported Tuberculosis in the United States, 2005
⁴ Reported Tuberculosis in the United States, 2005
⁵ Reported Tuberculosis in the United States, 2005
⁶ Reported Tuberculosis in the United States, 2005
⁷ Reported Tuberculosis in the United States, 2005
⁸ Reported Tuberculosis in the United States, 2005
⁹ Progressing Toward Tuberculosis Elimination in Low-Incidence Areas of the United States, MMWR 2002; 51(RR05); 1-16.