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 or 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.
• Greater than 80% of active TB cases in United States result from untreated LTBI (1).
• LTBI treatment is a key component of the TB elimination strategy for the United States.

Epidemiology

• In the United States, high-risk groups include immigrants from countries with a high TB rate (countries other than the United States, 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; persons living or working in high-risk congregate settings such as nursing homes, carceral facilities, and health care workers (3)
• TB is a major cause of death in individuals infected with HIV (3).
• Newly exposed (particularly children) are also at high risk.
• In 2020, there were 7,163 TB cases reported in the United States (4).
• In 2020, of the 7,163 TB cases, 71% of them were in non–U.S.-born persons (4). 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 TB, incidence in 2018 was highest among Asians, followed by Native Hawaiians/Pacific Islanders, non-Hispanic blacks (blacks), Hispanics, and American Indian/Alaska Natives and was lowest among non-Hispanic whites (whites) (1),(3).
• The highest TB incidence for U.S.-born persons occurred among Native Hawaiians/Pacific Islanders, followed by American Indians/Alaska Natives, blacks, Asians, and Hispanics and was lowest in whites (1).

Incidence
In 2018, a total of 9,029 new TB cases were reported in the United States (1).

Prevalence

• Globally, 10 million people were infected with TB in 2020. 1.1 million of these people were children (5).
• Globally, TB incidence fell about 2% per year between 2015 and 2020 (5).
• In the United States, there were 7,163 cases of TB reported in 2020 (4).

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
• Health care 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