Abstract & Commentary

TB in the U.S. — Things Continue to Improve, But There is a Long Road Ahead

By Stan Deresinski, MD, FACP, FIDSA, Clinical Professor of Medicine, Stanford University, Associate Chief of Infectious Diseases, Santa Clara Valley, Medical Center, is Editor for Infectious Disease Alert.

Source: CDC. Trends in tuberculosis – United States, 2011. MMWR 2012; 60:181-5.

Based on reports to the CDC National Tuberculosis Surveillance System, the rate of new TB cases in 2011 was the lowest since reporting began in 1953. A total of 10,521 cases were reported in 2011 for an incidence of 3.4 cases per 100,000 population — a decrease of 6.4% from the previous year.

Race/Ethnicity

While the incidence decreased in all racial and ethnic groups, in Asians it decreased by only 0.6%. while in non-Hispanic whites it decreased by 6.2%. In Hispanics the decrease was 7.2% and in non-Hispanic blacks it was 10.2%. Despite these reductions, the rate of incident cases (both new infection and reactivation disease) was 12 times higher in foreign-born individuals than in those born in the U.S. These relative changes in incidence led to Asians passing Hispanics as the largest group with TB for the first time since the current reporting system was instituted in 1993. Five countries of origin accounted for 54.1% of cases among foreign born: Mexico, the Phillipines, Vietnam, India, and China. The TB rate in (non-Hispanic) Asians was 7 times higher than in Hispanics, 8 times higher than in non-Hispanic blacks, and 25 times higher than in non-Hispanic whites. Among only U.S.- born groups, however, the rate of TB relative to non-Hispanic whites was greatest for non-Hispanic blacks whose rate was 6 times higher. Overall, the rate in all U.S.-born individuals was only 1.5 cases per 100,000 population, a 10.3% decrease since 2010 and an 80.1% decrease since 1993.

The States

The rates of TB per 100,000 population ranged from 0.7 in Maine to 9.3 in Alaska. Despite the overall decrease, 16 states and the District of Columbia had higher rates in 2011 than in 2010 (See Figure 1). Four states — California, Florida, New York, and Texas) accounted for approximately one-half of all TB cases reported in 2011.

Rate of Tuberculosis Cases

HIV Status, MDR TB, XDR TB

Among the 81% of cases for whom their HIV status was known, 7.9% were seropositive. A total of 109 cases of MDR TB were reported in 2010 (the most recent year for which complete results were available), representing 1.3% of those tested, a figure unchanged from the previous year. Among individual with no past history of treatment for tuberculosis, the percentage of MDR TB has remained stable at approximately 1.0% since 1997. Among those with a previous history of TB, the proportion with MDR TB was approximately 4 times higher. Foreign-born individuals accounted for 82.6% of the total MDR TB cases in 2010 and 4 cases of XDR TB have were reported in 2011, all occurring in foreign-born.

Commentary

These data indicate that, while the overall rates of tuberculosis are progressively decreasing in the U.S., TB continues to be a significant problem, especially among the foreign-born. Among the latter, Asians represent the group with the single highest incidence and the smallest year-to-year decrease. Almost 80% of cases among the foreign-born were diagnosed 2 or more years after entry into the U.S., suggesting that most were the result of reactivation of latent infection that had been acquired in their native lands. This observation supports an aggressive approach toward the detection and treatment of latent TB, something that may be facilitated by the use of once weekly directly observed treatment with rifapentine and isoniazid.

Despite this largely good story of a progressive decrease in the incidence of TB, it is estimated that, unless current efforts are improved and/or expanded, the goal of TB elimination in the U.S. will not be reached before the turn of the next century. As stated by CDC, "Initiatives to improve awareness, testing, and treatment of latent infection and TB disease in minorities and foreign-born populations might facilitate progress toward the elimination of TB in the United States. Progress toward TB elimination in the U.S. will require ongoing surveillance and improved TB control and prevention activities. Sustained focus on domestic TB control activities and further support of global TB control initiatives is important to address persistent disparities between non-Hispanic whites and racial/ethnic minorities and between U.S.-born and foreign-born persons."

Whether this can be accomplished in the current economic and political climate is uncertain, at best. The recent report of an outbreak of pulmonary TB in 26 homeless individuals with a chain of transmission from 2007-20111 is a case in point. In November 2010, while the outbreak was still going on (although it remained occult), the local public health department's workforce was reduced by 50%. Once before, TB control activities were reduced in this country, a move that was followed by a resurgence of case rates in the U.S. — will we ever learn?

Reference

  1. CDC. Tuberculosis outbreak associated with a homeless shelter – Kane County, Illinois, 2007-2011. MMWR 2012; 60:186-9.