Description

• Latent tuberculosis infection (LTBI) is an asymptomatic, noninfectious condition following exposure to an active case of tuberculosis (TB). LTBI is usually detected by a screening skin/blood test.
• Active TB occurs in 5–10% of infected individuals who have not received preventive therapy. Chance of active TB increases with immunosuppression and is highest for all individuals within 2 years of infection; 85% of the cases are pulmonary, which can be spread person-to-person via aerosol route.
• >80% of active TB cases in the United States result from untreated LTBI.
• LTBI treatment is a key component of the TB elimination strategy for the United States.

Epidemiology

• Epidemiology is difficult to assess because LTBI is not a reportable infection in many states.
• In the United States, high-risk groups include immigrants from countries with a high TB rate (countries other than Canada, Australia, New Zealand, or a country in western or northern Europe); persons with a history of drug use or experiencing homelessness; HIV-infected or immunocompromised individuals; and persons living or working in high-risk congregate settings such as nursing homes, carceral facilities, and health care facilities (2).
• Newly exposed (particularly children) are also at high risk.
• On average, 5–10% of those infected with LTBI will go on to develop active TB in their lives, typically within 5 years (1).
• In 2020, there were 7,163 TB cases reported in the United States. In 2020, of the 7,163 TB cases, 71% were non–U.S.-born persons. Incidence decreased in both populations; U.S. born decreased from 0.9 to 0.7 cases per 100,000, and non-U.S. born decreased from 14.2 to 11.5 cases per 100,000.
• Among non–U.S.-born persons with LTBI, prevalence was highest in persons who are Hispanic (37%) or of Asian or other race/ethnicity (36%).
• The highest TB incidence for U.S.-born persons occurred among people of non-Hispanic white race/ ethnicity, and the most likely medical diagnostic risk factor was a diagnosis of diabetes.

Incidence
There are no estimates for annual incidence of LTBI in the United States.

Prevalence
Globally, 2 billion people are estimated to be infected with TB. Globally, 10 million people were diagnosed with active TB in 2020. 1.1 million of these were children. Globally, TB incidence fell about 2% per year between 2015 and 2020. In the United States, there were 7,163 cases of TB reported in 2020; the CDC estimates 13 million people with LTBI (3).

Etiology and Pathophysiology

Mycobacterium tuberculosis, Mycobacterium bovis, and Mycobacterium africanum

Risk Factors

Immigrants from TB-endemic countries, which include most countries of Africa, Asia, and Eastern Europe; close contact with infected individual; living or working in a congregate setting (e.g., prison, nursing home); use of illicit drugs; lower socioeconomic status or experiencing homelessness; healthcare workers; laboratory personnel working with mycobacteria

General Prevention

• Screen for LTBI and treat individuals with positive tests.
• If a person has fibrotic lung changes on imaging and no evidence of TB treatment, these patients should be screened for LTBI, regardless of their other risk factors.
• Special population: Organ donors should be screened. If donor is deceased, IGRA testing is still possible.

Commonly Associated Conditions

• HIV infection (see “Initial Tests [lab, imaging]”)
• Immunosuppression
• IV drug use and substance use disorders