Page 110 - JSOM Winter 2021

Latent TB Infection in USSOF

A Refresher and Update

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Shawn H. Tang, 18D ; Joshua D. Evans, PA-C ;
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Alexander Vostal, MD ; Akira A. Shishido, MD *
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ABSTRACT
Tuberculosis (TB) causes approximately 2 million deaths an- clinically as fever and lymphadenopathy followed by the for-
nually worldwide, with 2 billion persons estimated to be ac- mation of cavitary lung lesions. Patients with LTBI cannot
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tively infected with TB. While rates of active TB disease in the transmit TB but have a 5–10% lifetime risk of reactivation of
US military are low, military service in TB-endemic countries infection (reactivation TB). Clinically, reactivation TB mani-
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remains an uncommon, but important source of infection. fests subtly as weeks to months of low-grade fever, weight loss,
United States Special Operations Forces (USSOF) and enablers and cough. Both primary TB and reactivation TB are consid-
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often operate in TB-endemic countries and, as an inherent risk ered active infection with the possibility of transmission.
of their mission sets, are more likely to have high-risk expo-
sure to TB disease. Military medical authorities have provided
excellent diagnostic guidance; the Centers for Disease Control Context
and Prevention (CDC) recently updated preferred regimens The US Army Medical Command (MEDCOM) Regulation
for the treatment of latent TB infection (LTBI). This review 40-64 now advises against routine testing of returning troops
serves as a refresher and update to the management of LTBI in and instead recommends targeted testing in all settings. The
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USSOF to optimize medical readiness through targeted testing principal risk factors for acquiring TB infection are outlined
and short treatment regimens. in Table 1 and include prolonged community residence in a
TB-endemic country, cohabitation with TB-endemic country
Keywords: military medicine; tropical medicine; tuberculosis; natives, and work at healthcare facilities or prisons in TB-
latent TB endemic countries. However, birth abroad remains the biggest
risk factor for TB in the military. Deployment or military ser-
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vice in TB endemic countries alone, even for prolonged peri-
ods, has not been shown to be a risk factor for acquiring TB in
Introduction the absence of these listed exposures. 9
Mycobacterium tuberculosis is an ancient pathogen that has
caused the human disease TB since early organized civiliza- TABLE 1 Principal Risk Factors for Acquiring Tuberculosis (TB)
tion. M. tuberculosis is an acid-fast bacilli and member of • Birth in a country with high incidence of TB disease
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the genus Mycobacterium. Currently, about a quarter of the • A weakened immune system
world’s population is estimated to be infected with M. tubercu- • Prolonged community residence in a TB-endemic country
losis, with approximately 10 million active infections globally • Residing with someone from a TB-endemic country
in 2019. USSOF and enablers often operate in countries with
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a high TB burden and, as an inherent risk of their mission sets, • Exposure to a person known to have infectious TB disease
are at increased risk of exposure to TB. This review serves as • Working or residing with people who are at high risk for TB
in facilities or institutions such as hospitals, homeless shelters,
a refresher and update for screening, diagnosis, and treatment correctional facilities, nursing homes, and residential homes for
of LTBI in the military. It specifically focuses on recent expe- those with human immunodeficiency virus
riences in SOF and considers newly updated CDC guidelines. Adapted from MEDCOM Regulation 40-64. 9
The most recent individual and unit deployment policy from
Clinical Disease
the US Central Command (CENTCOM) provides consistent
Infection occurs on inhalation of bacilli in respiratory droplets guidance recommending that targeted testing be performed in
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from a patient with active pulmonary infection. Although M. accordance with service policy and CDC guidelines. Addi-
tuberculosis can disseminate hematogenously, isolated pulmo- tionally, untreated LTBI is not a contraindication for deploy-
nary infection is most common in immunocompetent patients. ment and no waivers are required – however, Soldiers actively
Approximately 90% of initial infections are asymptomatic, on treatment may not deploy. The latest Army Medical
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and patients either clear the infection or progress to a latent Standards for Retention AR 40-501 state that LTBI warrants
form of the disease (LTBI). Approximately 10% of initial infec- treatment and Soldiers should be profiled while receiving
tions can progress to a pneumonia (primary TB), manifesting treatment. 11
*Correspondence to ashishido@som.umaryland.edu
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1 Shawn H. Tang is an 18D and affiliated with Uniformed Services University of Health Sciences, Bethesda, MD. Joshua D. Evans is a physician
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assistant with Tacoma Trauma Trust. Dr Alexander Vostal and Dr Akira A. Shishido are physicians affiliated with the University of Maryland
Medical Center Division of Infectious Diseases, Baltimore, MD.
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