World TB Day, March 24, 2003

Many people think that tuberculosis (TB) is a disease of the past, an illness that no longer threatens us today. This is not the case. Yes, TB has been afflicting humans for thousands of years, but it is by no means a disease of the past. Today in the 21st century, TB is still one of the leading global causes of death from infectious disease, even though it is readily treatable and preventable. Each year, approximately 8 million new cases of TB occur and there are more than 2 million TB-related deaths worldwide.

One reason for the belief that TB is a disease of the past is that in the United States (U.S.), we are currently seeing declines in TB, and are at an all-time low in the number of persons suffering with TB. This provides an opportunity to begin to make TB a disease of the past by eliminating it in the U.S. The possibility of eliminating TB in the U.S. was raised as early as the 1930s. The discovery in the 1950s of effective antimicrobial drugs to treat TB further advanced this idea. Finally, in the late 1960s the number of cases was low enough that this goal seemed within reach. However, as the number of TB cases continued to decline, so did interest in TB. This led to complacency about TB as a problem and neglect of public health TB control, coincident with the loss of categorical federal funding for TB control in the 1970s. This loss of funding resulted in a period of resurgence of TB and the occurrence of multidrug-resistant TB (MDR TB) in the U.S. during the late 1980s and early 1990s. The human suffering and death as well as the economic losses that occurred during this time were dramatic. However, due to renewed concern about TB, which led to additional TB resources in the early 1990s, the TB control infrastructure has since been revitalized, the resurgence trend reversed, and TB elimination appears once again within our reach if we are up to the challenge.

2001 data indicate there were 15,989 cases of active TB reported in the United States, representing a 2% decrease from 2000, a 40% decrease from 1992, and an all-time low of active TB cases.
2001 represents the ninth consecutive year that TB cases have declined, suggesting that the nation is fully recovered from the resurgence of TB that occurred in the late 1980s and is back on track toward TB elimination.

Although trends suggest that the nation is advancing toward elimination, significant challenges remain, particularly the increasing impact of the global TB epidemic on the U.S., the continued threat of multidrug-resistant TB (MDR TB), and the interaction between HIV and TB.

An increasing proportion of persons with TB were born in areas where TB is common, such as Asia, Africa, and Latin America. TB among individuals living in the U.S. but born in other countries increased from 4,925 (22% of national total) in 1986 to 7,865 (50% of national total) in 2001.
If individuals with active TB disease do not complete therapy for 6 months, they can develop and spread strains that are resistant to available drugs. During 1993-2001, 45 states and the District of Columbia reported cases of MDR TB. In 2001, 1% of people with culture-positive TB had MDR TB.
People coinfected with TB and HIV are up to 800 times more likely to develop active TB disease during their lifetime than people without HIV infection.

Throughout history, TB has had a disproportionate impact on men in the U.S. This trend was evident in the past decade.
In 2001, 62% (9,943) of TB cases occurred among men, and 38% (6,045) occurred among women. The rate of TB for men (7.1 per 100,000) was almost double that of women (4.2 per 100,000).

TB disproportionately affects minorities. In 2001, 79% of all reported TB cases in the U.S. occurred in racial and ethnic minorities.
In 2001, rates of TB were dramatically higher for Asians/Pacific Islanders (32.7 per 100,000), African Americans (13.8 per 100,000), Hispanics (11.9 per 100,000), and American Indians/Alaska Natives (11.0 per 100,000), than for whites (1.6 per 100,000).
In 2001, there were 4,796 African Americans reported as having TB disease; 3,357 whites; 4,001 Hispanics; 3,552 Asians/Pacific Islanders; and 233 American Indians/Alaskan Natives.
Several factors likely contribute to the disproportionate burden of TB on minorities. Among people from countries where TB is common, TB disease may result from an infection acquired in their home country. Among racial and ethnic minorities, unequal distribution of TB risk factors, particularly HIV infection, can also increase the chance of developing the disease.

Currently, the greatest proportion of TB cases occur among persons aged 25 to 44. Looking at the last decade, two trends by age group emerge:

During the resurgence, annual TB cases increased most dramatically in the 25- to 44-year-old age group, partially due to the influence of HIV infection and recent immigration of people in this age group from areas of high TB prevalence.
Since 1992, substantial declines in TB cases occurred in all age groups. An important factor in these declines is believed to be improved TB control in communities, especially in interrupting transmission.

A number of groups may be more likely to be exposed to or infected with TB than the overall population. These groups include health care workers, residents of long-term care facilities, people who are homeless, residents of correctional facilities, and people from countries where TB is common.

Residents of Correctional Facilities
Among residents of correctional facilities, 400-500 cases of TB are reported, accounting for 3%-4% of annual cases.

Homeless
Approximately 800-900 TB cases are reported among the homeless each year, accounting for 6% of annual cases.

Residents of Long-term Care Facilities
CDC receives 300-400 reports each year of TB cases among residents of long-term care facilities, accounting for 2%-3% of annual cases.

Health Care Workers
In recent years, CDC has received 300-400 reports each year of TB disease among health care workers, representing 2%-3% of annual cases.

One of the most dramatic changes in TB epidemiology over the past decade has been the impact of foreign-born persons on the incidence of TB within the U.S. For example, TB cases continue to decline nationally; however, the overall decrease in TB cases during 1991-2001 was primarily due to a 59% decrease in the number of U.S.-born cases. In contrast, the total number of U.S. cases among residents born outside the U.S. has remained at approximately 7,500 cases each year.
TB case rates in foreign-born persons remain substantially higher (approximately 8 times) than those in the U.S.-born population. During 1991-2001, the case rate in U.S.-born persons decreased from 8.2 TB cases per 100,000 population to 3.1, whereas the rates for people born outside the U.S. decreased minimally (from 33.9 to 26.6).

Risk factors (including substance use, homelessness, residence in a correctional facility, and HIV co-infection) for TB in U.S.-born patients are less commonly identified in foreign-born TB patients. The most important risk factor for TB among these patients appears to be previous residence in an area with a high rate of TB.

TB is a serious threat to people with weakened immune systems. In most people with normal immune systems the TB bacteria can be controlled by the body, and these people may never get sick. However, in people with weakened immune systems, the TB bacteria may not be kept in check; as a result, they are more likely to develop active TB disease. This high-risk group includes people with HIV infection, other specific medical conditions (such as diabetes or cancer), and people who inject drugs. Among people with TB infection, HIV is the strongest known risk factor for progressing to active TB disease.

In 1993, CDC began collecting information on HIV status for persons with TB disease. Reporting of this information has been limited. Less than 50% of TB case reports include HIV test results. CDC is working with state and local health departments to improve reporting of this information, particularly in people aged 25-44.
During 1993-2000*, the estimated percentage of HIV coinfection in persons of all ages with reported TB decreased from 15% to 9% overall and from 29% to 17% in persons aged 25-44. Much of the decline may be a result of intensified TB control efforts to interrupt transmission since 1992.

TB morbidity varies considerably by geographic location. In 2001, 23 states had a case rate at or below the Healthy People 2000 target rate of 3.5 cases per 100,000 people. On the other hand, seven states (California, Florida, Georgia, Illinois, New Jersey, New York, and Texas) that were above the national average accounted for 60% of the national total of TB cases. The proportion of foreign-born cases also varies by state; the number of states with at least 50% of their cases among people born outside the U.S. increased from 4 in 1991 to 23 in 2001.