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TB outbreaks linked to substance use, jail time, homelessness
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Substance abuse, incarceration and homelessness were among the characteristics of tuberculosis cases that had precipitated outbreaks between 2002 and 2011, according to researchers from the CDC and Emory University.
“Most patients reported excess alcohol or illicit drug use, half had been incarcerated at some point in the past, and nearly half had been homeless in the year before diagnosis,” they wrote in Emerging Infectious Diseases.
The researchers reviewed investigation reports on 26 TB outbreaks written by CDC staff. Each outbreak had more than three culture-confirmed cases with epidemiological links and TB strains with matching genotypes, and each had written identification of the initial source case in the transmission chain. Duration of each outbreak was calculated starting with the date of treatment initiation for the first reported case, and concluded with the treatment start date for the last case.
In 20 of the outbreaks, the source case-patient was the first to be reported to public health authorities. These patients (88% men) were aged 18 to 62 years, and 73% were born in the United States. The case-patients had long infectious periods (median, 10 months), the researchers said, and they often experienced delayed TB diagnosis and treatment. All of the patients had confirmed pulmonary TB diagnosed through positive acid-fast bacilli smear.
According to the researchers, 62% of the source case-patients reported heavy use of alcohol, 54% reported using illicit drugs, 50% had been incarcerated at some point in the past, and 42% had been homeless within the previous year. Most cases were identified because the patient sought care for TB symptoms rather than through contact investigations.
Of the outbreaks, nine were restricted to a single generation of spread from the source case-patient to the direct contact of the patient; the remaining 17 cases had further transmission waves extending beyond the source case-patient. The median duration of the outbreaks was 13 months (range, 4-151 months), and 242 cases (median, eight cases per outbreak) were identified.
In the four outbreaks in which the source case-patient had been incarcerated at diagnosis, the outbreak size ranged from seven to nine cases. For the 11 outbreaks in which the source case-patient had been homeless at some point during the past year, the median outbreak size was nine cases.
“This review underscores the particular importance of prompt and thorough investigations for TB cases confirmed by positive smear for acid-fast bacilli in which patients have experienced substance abuse, incarceration, or homelessness,” the researchers wrote. “Public health departments should work with local health care providers to address barriers to accessing care faced by marginalized populations and in recognizing and diagnosing TB once symptomatic patients seek medical attention.” – by Jen Byrne
Disclosure: The researchers report no relevant financial disclosures.
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