Background

Over 9,600 cases of tuberculosis (TB) were diagnosed in the United States in 2023, a 16% increase over the previous year. ^{Reference Williams, Pratt, Walker, Price, Stewart and Feng1} When an individual is diagnosed with potentially contagious TB, public health agencies initiate a case investigation, which identifies individuals who have been in close contact with the index patient and provides them with recommendations for testing and, if necessary, treatment. The rapid identification of child contacts is particularly important as younger children have a higher risk of developing symptomatic tuberculosis disease. ^{Reference Marais, Gie and Schaaf2} Additionally, the very young are more likely than other age groups to develop miliary, extrapulmonary, or meningeal TB acutely following infection. ^{Reference Marais, Gie and Schaaf2} The CDC and WHO designate children <5 years of age exposed to TB as high-risk contacts who should be evaluated for window prophylaxis. ^{Reference Taylor, Nolan and Blumberg3,4} Window prophylaxis is the administration of preventive antibiotic treatment to those who have been exposed to TB but have not yet developed symptoms or tested positive by immunologically based assays, and is recommended during the period between initial exposure and a follow-up test 8–10 weeks later to prevent the development of active TB. ^{Reference Taylor, Nolan and Blumberg3,4} While it is known that the risk of TB infection increases with a longer exposure period, ^{Reference Reichler, Khan and Yuan5} the duration of exposure time resulting in high-risk status has not been well described. Additionally, the density of infectious droplet nuclei in the air at the time of exposure and the ventilation capability of the environment also contribute to the risk of exposure. ^{Reference Taylor, Nolan and Blumberg3}

Public health response to community TB exposure

This report details a public health response to a TB exposure at a Young Men’s Christian Association (YMCA) drop-in daycare center. The internationally infected source patient, without underlying health conditions, exhibited signs and symptoms of active pulmonary TB for three months before being diagnosed. This resulted in a potential exposure period totaling six months. ^{Reference Sterling, Njie and Zenner6}

Clinical findings of the index patient included a computed tomography scan showing a partially cavitary 7 mm right lung apex nodule, positive smear microscopy, GeneXpert MTB/RIF PCR, and AFB culture with Mycobacterium tuberculosis identified. The daycare consisted of a 1,473-square-foot room equipped with a standard HVAC system. The daycare utilized an electronic badge system to record the entry and exit of each child into the daycare center, allowing for highly accurate identification of contacts and exposure times.

A total of 592 individuals had exposures related to the drop-in daycare, of which 359 were <5 years of age. Of those <5,211 had been exposed within the prior 10 weeks and were offered evaluation for window prophylaxis (Table 1). Cumulative exposure times ranged from 26 minutes to over 21 hours (Figure 1). The public health department, in consultation with the CDC’s Division of Tuberculosis Elimination, notified families with more than 30 minutes of documented exposure through multiple communication channels. These included emails (using contact information from YMCA membership profiles), phone calls, a public meeting, a press conference, and several press releases. Families were advised on patient-specific evaluations based on the last known exposure date. Individuals ≥5 years old or <5 years but more than 10 weeks from last exposure were offered TB testing at clinics set up at the YMCA (interferon- $\gamma $ release assay [IGRA] ≥2 years or tuberculin skin test <2 years old). Individuals <5 years old and <10 weeks from exposure were referred to a TB Exposure Clinic developed in cooperation with the local children’s hospital where they had an exam performed by a provider, had chest x-ray and TB testing performed, and if indicated, initiated on prophylactic medication.

Table 1. Demographics of tuberculosis exposures at YMCA

Figure 1. Cumulative time of tuberculosis exposure by age.

A 1-step testing strategy was utilized for individuals with exposure ≥10 weeks from last contact and a 2-step testing strategy was utilized for those with <10 weeks from last exposure. ^{Reference Sterling, Njie and Zenner6} Overall, 298 of 592 (50.3%) exposed individuals received recommended testing. Of the 211 individuals eligible for window prophylaxis (<5 years of age and <10 weeks from exposure), 107 of 211 (50.7%) completed initial testing, and 75 of 211 (35.5%) completed follow-up testing. Out of 211 individuals eligible for window prophylaxis, 92 (43.6%) initiated therapy. Notably, the acceptance rate increased to 93.7% (119 of 127) among those who were evaluated by a provider. As of this writing, none of the individuals identified in this community exposure have developed TB infection, and there are no known cases of TB disease among the non-household contacts.