Limited Utility of Name-Based Tuberculosis Contact Investigations among Persons Using Illicit Drugs: Results of an Outbreak Investigation

Abstract

Persons named by a patient with tuberculosis (TB) are the focus of traditional TB contact investigations. However, patients who use illicit drugs are often reluctant to name contacts. Between January 2004 and May 2005, 18 isoniazidresistant TB cases with matching Mycobacterium tuberculosis genotypes (spoligotypes) were reported in Miami; most patients frequented crack houses and did not name potentially infected contacts. We reviewed medical records and reinterviewed patients about contacts and locations frequented to describe transmission patterns and make recommendations to control TB in this population. Observed contacts were not named but were encountered at the same crack houses as the patients. Contacts were evaluated for latent TB infection with a tuberculosis skin test (TST). All 18 patients had pulmonary TB. Twelve (67%) reported crack use and 14 (78%) any illicit drug use. Of the 187 contacts evaluated, 91 (49%) were named, 16 (8%) attended a church reported by a patient, 61 (33%) used a dialysis center reported by a patient, and 19 (10%) were observed contacts at local crack houses. Compared to named contacts, observed contacts were eight times as likely to have positive TST results (relative risk=7.8; 95% confidence interval=3.8-16.1). Dialysis center and church contacts had no elevated risk of a positive TST result. Testing observed contacts may provide a higher yield than traditional name-based contact investigations for tuberculosis patients who use illicit drugs or frequent venues characterized by illicit drug use.

Tuberculosis Outbreak Investigations in the United States, 2002–2008

“…To optimize the yield of contact investigation, the 2 interventions most frequently used in these outbreaks were prioritizing screening of contacts on the basis of TB risk ( 3 , 5 , 6 , 8 – 11 , 18 ) and offering location-based TB screening at specific venues associated with each outbreak, including bars, shelters, and drug houses ( 5 , 6 , 10 , 13 , 14 ). Although this intervention is resource-intensive, its benefits have been recognized in several investigations involving hard-to-reach populations ( 10 , 14 , 31 ). In 1 outbreak, unnamed contacts encountered at a drug house frequented by numerous TB patients were offered screening and were found to be 8× more likely to have a positive tuberculin skin test result than were named contacts ( 10 ).…”

“…Although this intervention is resource-intensive, its benefits have been recognized in several investigations involving hard-to-reach populations ( 10 , 14 , 31 ). In 1 outbreak, unnamed contacts encountered at a drug house frequented by numerous TB patients were offered screening and were found to be 8× more likely to have a positive tuberculin skin test result than were named contacts ( 10 ). …”

A Tuberculosis Outbreak Fueled by Cross-Border Travel and Illicit Substances: Nevada and Arizona

“…This approach of finding close contacts might be useful in other outbreaks involving hard-to-reach populations, in whom name-based contact investigations are known to be challenging. 13,34 Approximately 5%-10% of people with LTBI develop TB disease and represent future cases that could have been prevented. 13 Prospective surveillance of genotyped cases indeed detected additional cases linked to this outbreak.…”

Outbreak of pyrazinamide-monoresistant tuberculosis identified using genotype cluster and social media analysis

“…Limitations of this approach have been reported, particularly when applied to populations at high risk for TB transmission, including adults with substance dependence, who may be unwilling or unable to report contacts. 20 Social media have been employed to publicize health information, and have increasingly been used as an ‘infodemiology’ tool to monitor online behavior to evaluate trends in illnesses such as influenza. 21 However, its use as an outbreak investigation tool remains in its infancy.…”