Tuberculosis cases are on the decline in the US and Europe, according to new reports from the US Centers for Disease Control and Prevention (CDC) and the European Centre for Disease Prevention and Control (ECDC).
Cases among those of foreign origin, however, pose problems for disease elimination. The updated numbers were released today, in light of World TB Day.
US sees fewer cases, exception in foreign-born
According to a study today in Morbidity and Mortality Weekly Report (MMWR), TB cases in 2016 declined slightly from the previous year, at an incidence rate of 2.9 cases per 100,000 people, which is 3.4% less than 2015's rate. In 2016, a total of 9,287 new TB cases were diagnosed, down 2.7% from 2015.
TB cases have been declining in the US each year since 1993. In 2015, however, cases rose and the incidence rate remained steady. But despite 2016's decline, epidemiologic models show that at this rate, TB would not be eliminated from the United States by the end of the century.
"Although TB case counts and incidence are decreasing in the United States, progress is insufficient to achieve in this century the goal of TB elimination," the report states. "Measures to diagnose and treat active TB disease must continue, and new strategies aimed at accelerating progress toward TB elimination in the United States, such as targeted testing for and treatment of [latent TB], should also be employed."
According to the report, TB incidence among US-born persons (1.1 cases per 100,000) decreased 8.4% from 2015, and incidence among foreign-born persons (14.6 cases per 100,000) decreased 3.2% from 2015. US-born persons accounted for 2,935 (31.6%) of the new cases in 2016 cases, while 6,307 (67.9%) of the cases occurred in foreign-born people.
Among US-born people, American Indian/Alaska Natives and Native Hawaiian/Pacific Islanders still have the highest incidence of the disease, at 5.0 and 9.2 per 100,000, respectively.
Among the foreign-born, those born in Asia (26.9 cases per 100,000), non-Hispanic black people (22.3), and Hispanics (10.0) had the highest rates of TB. The top countries of origin for foreign-born people with TB in 2016 were Mexico (18.9%, 1,194 cases), the Philippines (12.6%, 795), India (9.4%, 593), Vietnam (7.9%, 496), and China (6.1%, 383).
In another MMWR note, authors highlight the importance of testing foreigners who have been in the States for more than a decade from countries that have high rates of TB. Since 2013, the CDC has seen a rise in TB cases in older foreign-born persons, because latent infections missed at testing that took place upon immediate arrival in the country can be reactivated years later.
According to the CDC, the number and proportion of TB cases among foreign-born persons who arrived in the United States more than 10 years before diagnosis increased from 1,360 (18.4%) in 1993 to 2,922 (46.0%) in 2015. In fact, the CDC estimates that 92.5% of TB cases in foreign-born persons are from latent infections.
Europe notes similar trends in migrants
The ECDC, meanwhile, reported new TB numbers yesterday and echoed the US trend of overall case decline, but stubborn rates of the disease among migrants from high-incidence countries.
From 2010 to 2015, 29 countries reported 404,551 TB cases. Of 394,110 cases for which information on origin was available, 283,426 (71.9%) involved people born in or citizens of the reporting country, and 110,684 (28.1%) patients were of foreign origin. According to the agency, the proportion of cases in people with foreign origin increased from 25.9% in 2010 to 31.1% in 2015.
The increase, though, is not caused by an increase in immigration patterns (foreign-born residents remained at about 10% of the population). Instead, reactivation of latent infection acquired in home countries was likely to blame for the rise in cases, similar to the US situation.
"TB cases of foreign origin are and will remain a challenge for TB elimination, especially in low-incidence countries where they account for a substantial proportion of TB cases," the ECDC said.
As asylum seekers and migrants continue to relocate to Europe, the ECDC said an international effort of testing, treatment, and surveillance must be put in place to stop the spread of TB.
World TB Day
In related news, the World Health Organization (WHO) released several fact sheets on TB to mark World TB Day. In 2015, 1.8 million people died from TB, which continues to be one of the top 10 causes of death globally. Just six countries—India, Indonesia, China, Nigeria, Pakistan, and South Africa—account for 60% of the cases.
Though TB has declined an average of 1.5% per year since 2000, that rate needs to jump to 4% to 5% to meet the 2020 deadline in the WHO's campaign to end the disease.
Mar 24 MMWR report
Mar 24 MMWR foreign report
Mar 23 ECDC report
Mar 24 WHO TB information