CDC: TB Incidence Has Plateaued in US After 20-Year Decline

Troy Brown, RN

March 25, 2016

Tuberculosis (TB) incidence in the United States has leveled off after declining annually for 20 years, according to a new report published in the March 25 issue of the Morbidity and Mortality Weekly Report. The report highlights the need for intensified eradication efforts in the United States and globally, with increased emphasis on improving systems for identifying and treating latent TB infection and interrupting TB transmission in the United States, as well as reducing the incidence of TB globally.

In a separate report, the Centers for Disease Control and Prevention (CDC) notes that two thirds of TB cases in the United States occur in foreign-born individuals, and the agency urges clinicians near seasonally driven tourist destinations to be aware of the risk for TB in temporary visa holders who work in the tourism industry.

Since 2013, the incidence of TB in the United States has remained at approximately 3.0 new cases per 100,000 persons, according to data reported to the National Tuberculosis Surveillance System. The incidence of TB among foreign-born individuals in the United States has remained approximately 13 times that among US-born persons (15.1 cases per 100,000 vs 1.2 cases per 100,000).

In contrast, prior studies showed an annual decline of 0.2 or more cases per 100,000 persons for each of the last 20 years, according to Jorge L. Salinas, MD, from the Epidemic Intelligence Service and the Division of Tuberculosis Elimination, National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention, CDC, Atlanta, Georgia, and colleagues.

"[E]ven if the previously observed annual declines in the United States had been sustained, TB elimination, defined as < 1 TB case per 1 million persons annually, would not occur by the end of this century," they write.

In 2015, 9563 TB cases were reported in the United States. Of those, 3201 occurred among US-born persons and 6335 occurred among foreign-born persons in the United States. Half (4839) of those occurred in just four states (California, New York, Florida, and Texas), with each state reporting more than 500 cases.

During 2015, most TB cases among US-born persons were in non-Hispanic blacks (1144 cases) or non-Hispanic whites (991 cases). Among US-born non-Hispanic blacks, the incidence was the lowest ever, with 3.3 cases per 100,000 persons. In addition, TB incidence among US-born non-Hispanic whites remained at its lowest, with 0.5 cases per 100,000 persons.

Meanwhile, US-born Hispanics had the third highest case count (661 cases), but the second lowest incidence (1.8 cases per 100,000). TB incidence was highest among US-born Native Hawaiians/other Pacific Islanders (12.7 cases per 100,000), followed by US-born American Indians/Alaska Natives (6.8 cases per 100,000).

One tenth (10.7%; 344 cases) of incident TB cases reported in 2015 occurred in persons younger than 15 years (0.6 cases per 100,000).

Foreign-Born Individuals in the United States

In 2015, among foreign-born persons, Asians had the highest case count (3007 cases) and the highest incidence (28.2 cases per 100,000).

In terms of countries of origin, Mexico (n = 1250; 19.7%), the Philippines (n = 819; 12.9%), India (n = 578; 9.1%), Vietnam (n = 513; 8.1%), and China (n = 424; 6.7%) were the top five for foreign-born persons with TB in the United States in 2015. These five countries make up 45.2% of the foreign-born population in the United States, but they accounted for 56.6% (3584 cases) of all TB cases in foreign-born persons.

Although the largest proportion of TB cases among foreign-born persons occurred in Mexico-born persons, their incidence of TB in the United States (10.4 cases per 100,000) was lower than that among individuals born in China (24.9 cases per 100,000), India (23.9 cases per 100,000), the Philippines (46.9 cases per 100,000), and Vietnam (47.8 cases per 100,000).

From 2014 to 2015, the number of TB cases among Philippines-born persons rose from 755 to 819, for an increase of 8.5%. The number of cases among India-born persons rose from 479 to 578, for an increase of 20.7%.

A total of 96 (1.5%) TB cases reported among foreign-born persons in 2015 occurred in those younger than 15 years (6.0 cases per 100,000).

US, Global Strategies Needed

"Effective TB control requires diagnosing cases as early as possible during the illness, thus allowing earlier airborne precautions and curative treatment to interrupt transmission," the authors write. "An early diagnosis for a patient with infectious TB also permits a timely contact investigation, which is essential to detect and prevent additional TB cases."

These measures are particularly important for groups that are disproportionally affected by TB, the authors note. TB cases in foreign-born persons often occur years after arrival to the United States, which is consistent with untreated latent infection. Thus, additional strategies for reducing TB in the countries of origin and expanding treatment of latent infection among foreign-born persons are needed.

"These include increasing case detection and cure rates globally, reducing TB transmission in institutional settings such as health care settings and correctional facilities, and increasing detection and treatment of preexisting latent TB infection among the U.S. populations most affected by TB," the authors explain. "Finally, more emphasis should be placed on interrupting the relatively limited, but persistent, ongoing TB transmission (e.g., among persons experiencing homelessness) in the United States, as well as continuing research on better means to diagnose, treat, and prevent TB infection and disease," they conclude.

Increased Risk Among Seasonal Workers in Tourist Destinations

In a separate report also published in the March 25 issue of the Morbidity and Mortality Weekly Report, Meghan P. Weinberg, PhD, from the Epidemic Intelligence Service, CDC, and the Michigan Department of Health and Human Services, and colleagues urge healthcare providers to be aware of the increased risk for TB among temporary visa holders working in the tourism industry.

"Under the Immigration and Nationality Act, TB screening is required for persons seeking permanent residence in the United States (i.e., immigrants and refugees), but it is not routinely required for nonimmigrants who are issued temporary visas for school or work," Dr Weinberg and colleagues explain.

The authors describe three TB cases in foreign-born temporary workers during 2012 to 2014: two from the Philippines and one from South Africa. All lived in dormitory-style housing. In two of the cases, contact investigations were hampered by the fact that coworkers had left the area and were unreachable. All the cases went undetected until the patient sought medical care for symptoms, and one patient sought medical care five times before being diagnosed after 3 months. All these factors could have increased the likelihood of TB transmission, the authors write.

Clinicians, public health authorities, and employers all need to be aware of the potential for active TB among this population.

"Public health authorities might consider providing TB education for employers and clinicians in the tourism sector. Employers might consider implementing TB screening for temporary workers from countries with a high incidence of TB cases, and all employers should encourage employees to seek medical attention early during the course of an illness. Clinicians should promptly recognize TB signs and symptoms and inquire about previous travel to or residence in countries with a high incidence of TB cases," the authors explain.

"Until global TB elimination is reached, increased TB awareness among clinicians serving foreign-born temporary workers, followed by prompt treatment and public health follow-up after active TB is diagnosed, is necessary to reduce the potential for TB transmission," Dr Weinberg and colleagues conclude.

The authors have disclosed no relevant financial relationships.

Morb Mortal Wkly Rep. 2016;65:273-278. Salinas full text, Weinberg full text

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