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Epidemiologic Notes and Reports Drug-Resistant Tuberculosis among the Homeless -- Boston
In the period February 1984-March 1985, 26 confirmed cases of tuberculosis (TB) were reported among homeless people in Boston (Figure 1). All 26 cases have been associated with three large shelters. The estimated total population of homeless people in Boston is 6,000. Nineteen of the 26 cases were counted in 1984; this represents an incidence of 316.7 per 100,000, a greater than sixfold increase over the 1983 case rate of approximately 50.0/100,000. By comparison, the TB case rate for the rest of Boston in 1984 was 19.0/100,000, and the rate for Massachusetts excluding Boston was 4.8/100,000.
The outbreak was recognized because of reports among the homeless of a number of TB cases due to multiresistant organisms. As a result of this recognition, a screening program using Mantoux tuberculin skin tests, chest roentgenograms, and sputum examinations was implemented in November 1984. The program was carried out during a 4-night period in Boston's three largest shelters--those associated with the present outbreak. An average of 754 persons stayed at the three shelters on each screening night; all who agreed were screened. Chest x-rays were obtained for 438 persons; sputum was obtained from 274 for microscopic examination and culture. Skin tests were done on 350 people; 185 (52.9%) returned for reading, and of these, 34 (18.4%) had a 10-mm or larger reaction. As a result of the screening, five of the 26 TB cases were detected.
Other case-finding/control measures have included educational outreach efforts for the staffs of all Boston shelters, with an emphasis on rapid medical referral of clients presenting with a clinical picture suggesting TB. Two of the 26 individuals with TB were identified by this method after the screening in November.
Of the 26 TB patients, one is hospitalized, two have died, one has moved out of the state, and 22 are under outpatient treatment. Thirteen of these 22 are on directly observed therapy (drug ingestion observed by a health-care provider).
To date, sputum cultures from 23 of the 26 homeless patients have been bacteriologically confirmed as containing Mycobacterium tuberculosis. Fourteen (60.9%) of the 23 patients had organisms that were resistant to both isoniazid (INH) and streptomycin (SM); all 14 of these persons had spent time at the same shelter. One additional patient had organisms resistant to INH only, and another had organisms resistant to ethambutol (EMB) only.
Isolates from 21 of the 23 bacteriologically proven cases among the homeless and 13 control cultures from Boston residents not known to be associated with the outbreak have been phage typed at CDC. Thirteen isolates from the homeless were phage type 8 (7,9,12,13,14,15). Eleven of these were resistant to INH and SM, and one was resistant to EMB; one was susceptible to all drugs tested. Only one of the 13 control cultures was resistant to INH and SM and of the outbreak phage type. The individual from whom this culture was obtained denies any association with the homeless population.
Two individuals are suspected sources for the other cases with INH- and SM-resistant bacilli of the outbreak phage type. One, diagnosed in December 1983, was a 33-year-old man with a history of alcohol abuse who frequented a 350-bed Boston shelter. He had had a significant tuberculin skin-test reaction in 1973. He had twice begun preventive therapy but had not continued for more than a total of 2 months. In December 1983, a chest roentgenogram revealed extensive bilateral cavitary disease, and sputum smears contained many acid-fast bacilli (AFB). A second possible source, a 57-year-old man with schizophrenia, had a history of TB previously treated in 1980. Sputum cultures were negative; the diagnosis was clinically established. He was hospitalized and treated with multiple drug regimens that initially included INH, SM, and rifampin (RIF). He completed 2 months of inpatient therapy, and a total of 14 months of biweekly and then daily supervised therapy as an outpatient. He showed roentgenographic and clinical improvement. In July 1984, he presented with cough and a new infiltrate on his chest roentgenogram; sputum smears contained many AFB.
A voluntary program of active surveillance for clients and staff using skin testing alone is being introduced in all Boston shelters; to date, 13 of the 84 staff members tested at the 350-bed shelter have had tuberculin skin-test conversions. Preventive therapy with either RIF alone or INH and RIF is being recommended for these individuals. Reported by J Bernardo, MD, Boston City Hospital, Boston University School of Medicine, E Brigandi, B Blakeney, B McInnis, B Richards, Health Care for the Homeless, Boston, C Wall, L Shirley, MA Barry, MD, Boston Department of Health and Hospitals, T Kearns, S Weidhaas, B Thomas, E Nardell, MD, Div of Tuberculosis Control, DL Johnson, Mycobacteriology Laboratory, Massachusetts Department of Public Health; Div of Bacterial Diseases, Center for Infectious Diseases, Div of Tuberculosis Control, Center for Prevention Svcs, CDC.
Editorial Note: High rates of TB in homeless populations have been noted previously (1), although a large outbreak such as the one reported here has not been previously documented. A high incidence of disease in this population is not unexpected because TB case rates are higher in lower socioeconomic groups (2). Furthermore, stress, alcoholism, drug addiction, and low body weight, which are probably more common among the homeless, have been reported to increase the risk of TB (3-6). While shelters for the homeless are vital, this outbreak points out the potential danger of transmission of TB when large numbers of homeless persons come together.
Outbreaks of TB can be difficult to detect because of the relatively long and variable incubation period of the disease. In this outbreak the drug-resistance patterns of tubercle bacilli served as a marker for the recognition of the outbreak. If an outbreak is suspected among patients with drug-susceptible organisms, phage typing of cultures may be helpful.
Screening and follow-up is difficult in a transient population. The use of incentives, such as food and food vouchers, has been reported to enhance compliance with screening and drug therapy (7,8). Shelter employees should learn the signs and symptoms of TB and refer shelter clients with these signs and symptoms for an examination. For those with TB, outpatient treatment using directly observed therapy on a daily or twice weekly basis to ensure compliance is likely to be more cost effective than long-term hospitalization. Directly observed therapy for noncompliant and potentially noncompliant patients is important to prevent treatment failure, perhaps with the emergence of resistance to additional drugs, and to prevent continued transmission of infection.
Transmission of INH-resistant organisms to contacts presents a difficult problem with regard to preventive therapy. The only drug of proven value in preventing tuberculosis is INH. Because of the high probability that shelter employees with tuberculin-skin-test conversions were infected with INH-resistant organisms, preventive therapy with a regimen including RIF was used. Although the efficacy of preventive treatment with RIF has not been demonstrated in controlled trials, the results of a survey of TB experts to determine the choice of preventive treatment for INH-resistant TB infection support the use of RIF (9).
Staff of shelters for the homeless should receive a tuberculin skin test upon employment and every 6-12 months thereafter. Skin-test converters should be considered for preventive therapy according to current guidelines (10).
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