TB cases hit record low in US, but progress toward elimination lags

The United States recorded a record-low number of tuberculosis cases in 2016, but progress toward eliminating the disease in the U.S. by the end of the century has lagged, CDC experts said.

According to provisional data released by the CDC ahead of World TB Day, there were 9,287 new TB cases in the U.S. last year, the lowest number since reporting began in 1953 and a 2.7% decline from 2015. There was a 3.4% drop in the incidence rate to 2.9 cases per 100,000 people, but these declines were categorized as sluggish in a new MMWR.

“The findings suggest that unless progress against TB is accelerated in the United States, we will not be able to eliminate TB in the near future, or even this century,” Philip LoBue, MD, director of the Division of Tuberculosis Elimination in the CDC’s National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention, said in a statement.

LoBue said eliminating TB in the U.S. means not only diagnosing and treating active cases of the disease, but also identifying cases of latent TB infection (LTBI), which occurs when a patient is infected with Mycobacterium tuberculosis without signs or evidence of infection. According to LoBue, more than 85% of TB cases in the U.S. are caused by a reactivation of LTBI.

“Given the severity of this disease, it is essential that we maintain and strengthen TB health programs that prevent ongoing person-to-person transmission. Unfortunately, these efforts alone will not be sufficient,” LoBue said. “It’s estimated there are up to 13 million people living in the U.S. with latent TB infection; and while they do not have symptoms and cannot spread the bacteria to others, 5 to 10 percent of them will eventually develop active TB disease if left untreated.”

In the MMWR report, Kristine M. Schmit, MD, MPH, Epidemic Intelligence Officer in the Division of Tuberculosis Elimination, and colleagues said approximately 90% of TB cases in foreign-born people in the U.S. — which account for much of the national burden — are caused by reactivation of LTBI. Health organizations including the CDC and the independent U.S. Preventive Services Task Force (USPSTF) recommend that physicians proactively test for LTBI in patient populations considered at high risk, including immigrants from — or travelers to — high-burden countries such as China, India, the Philippines and Vietnam, and current or former residents of high-risk settings like homeless shelters, correctional facilities and long-term care facilities. Tests for LTBI include the tuberculin skin test and interferon-gamma release assay.

“The current recommendation from the USPSTF to test persons at increased risk regardless of length of time in the United States is in keeping with evidence that reactivation of LTBI remains a substantial concern, even in foreign-born persons who have lived in the United States for many years,” Schmit and colleagues wrote.

The median TB incidence rate among U.S. states last year was 1.9 per 100,000 people, according to Schmit and colleagues. Four states — California, Florida, New York and Texas — accounted for more than 50% of new cases. Hawaii had the highest incidence rate at 8.3, whereas Wyoming’s rate, 0.2, was the lowest.

Around 68% of all new TB cases in the U.S. were in foreign-born patients. The incidence rate among this group was highest in Asians at 26.9 cases per 100,000 people, but more patients with TB came from Mexico — 1,194 — than any other country.

According to a second MMWR report, since 2013, the number of new TB cases among foreign-born patients who have been in the U.S. for a decade or more exceeded the number of cases diagnosed in those who have been in the U.S. for under 10 years. Clarisse A. Tsang, MPH, also from the Division of Tuberculosis Elimination, and colleagues said this shows that prevention efforts “might need to be expanded beyond the public health sector to include private providers and community health centers to better reach populations that have lived in the United States for [at least] 10 years.”

LoBue said treating a patient with drug-susceptible TB costs approximately $18,000 — around 36 times more than treating a patient with LTBI. It is far more expensive still to treat drug-resistant TB, which can cost between $154,000 to $494,000, according to LoBue. (There were no available data for new drug-resistant TB cases in the U.S. in 2016. In 2015, 88 cases of multidrug-resistant TB and one case of extensively drug-resistant TB were reported, according to Schmit and colleagues.)

“TB is a preventable and curable disease,” he said. “We’ve come a long way in fighting the disease in the past century, but in order to reach TB elimination, we must intensify our efforts and implement a dual approach to put an end to a disease that has plagued mankind for thousands of years.” – by Gerard Gallagher

References:

Schmit KM, et al. MMWR Morb Mortal Wkly Rep. 2017;doi:10.15585/mmwr.mm6611a2.

Tsang CA, et al. MMWR Morb Mortal Wkly Rep. 2017;doi:10.15585/mmwr.mm6611a3.

Disclosure : LoBue and the researchers report no relevant financial disclosures.