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Interstate Outbreak of Drug-Resistant Tuberculosis Involving Children -- California, Montana, Nevada, Utah
As of September 30, six cases of tuberculosis (TB) and an additional 53 persons with significant reactions* to the tuberculin skin test have been identified in an outbreak of TB in California, Montana, Nevada, and Utah.
In November 1982, a 19-month-old child in Missoula, Montana, was diagnosed as having TB based on hilar adenopathy on chest radiograph and a significant tuberculin skin test reaction. The child's only known contact with a person having a history of TB was with a 30-year-old woman who was a close family friend and the child's babysitter.
The woman submitted to diagnostic evaluation in February 1983. Her chest film showed a 5-cm right apical cavity. A sputum culture yielded Mycobacterium tuberculosis; 50% of the organisms were resistant to isoniazid (INH). Subsequently, this patient's husband was found to have a large lesion in the right pleura and was sputum-culture positive for M. tuberculosis sensitive to INH. M. tuberculosis isolates from both the woman and her husband were identified as phage type 2 (7, 12, 13).
The woman had many social contacts. Besides working as a babysitter and having part-time jobs that brought her into frequent contact with the public, she was extremely active in a variety of church, community, and school activities. As part of the investigation, over 1,000 persons have been skin tested in Montana. These include over 200 persons who had identifiable contact with the woman, as well as over 500 persons who belonged to groups potentially exposed to her.
Three other cases were identified. All were in children 3-4 years of age who had significant tuberculin skin test reactions and pulmonary infiltrates and/or respiratory symptoms. For these three cases, the exposure to the woman was either through babysitting or family visits. All patients are being treated with multiple drugs to which the INH-resistant organisms are susceptible.
To date, 37 reactors (persons with significant tuberculin skin test reactions) have been identified in Montana. Of these, 31 had identifiable contact with the 30-year-old woman. The remaining six reactors had contact with the other cases. All reactors are taking rifampin as preventive therapy. Nine other reactors in Nevada and Utah and one reactor in California have been identified, all among relatives and friends of the woman. Contacts have also been identified in Illinois, Oklahoma, Washington, and Wyoming; to date none of these contacts who have been skin tested have shown a significant reaction.
Investigation of the woman's medical history revealed that in January 1979 in Nevada, she had been diagnosed as having TB; at the time, she had a 3-cm right apical cavity and a sputum culture that yielded M. tuberculosis sensitive to INH. She was treated with INH and ethambutol. After diagnosis of her illness, an additional 11 persons in Utah and Nevada were identified as having significant tuberculin skin test reactions; all reactors were relatives or friends of the woman. Eight months after diagnosis, she moved to Missoula, Montana, with a 3-month supply of medicine. However, she did not complete her course of treatment.
Of the six cases in the outbreak, four patients (67%) are under 15 years of age. Of the 53 reactors who have also been identified, 25 (47%) are under 15 years of age. Thus, nearly half (29/59) of the infected persons are children.
Still pending is an analysis to determine reactor rates for persons in different exposure categories and reactor rates by duration of exposure to the presumed source of infection. Reported by HA Renteln, MD, J Chin, MD, State Epidemiologist, California Dept of Health Svcs; Y Bradford, H Ezell, B Finley, D Lang, E Montgomery, W Newcomer, M Taylor, J Veleber, Missoula City-County Health Dept, D Bean, B Desonia, E Kelly, R Nelson, R Paulsen, F Sweeney, J Gedrose, State Epidemiologist, Montana State Dept of Health and Environmental Sciences; J Brophy, C Hess, D Knesek, M Meador, G Reynolds, MD, Acting State Epidemiologist, Nevada State Dept of Human Resources; D Forster-Burke, MA Miller, Tooele County Health Dept, E Butler, B Holmes, BL Larson, A Nelson, RE Johns Jr, MD, State Epidemiologist, Utah State Dept of Health; Div of Tuberculosis Control, Center for Prevention Svcs, CDC.
Editorial Note: This outbreak has several important facets. The first is that of drug resistance. While it is difficult to pinpoint the reason why INH resistance developed in the woman presumed to be the source of infection, probably the most important factor was that the patient failed to complete her treatment. Patients being treated for TB should be carefully monitored for compliance until the recommended course of therapy is completed.
Of note was the fact that both the woman and her husband had the same M. tuberculosis phage type, while only the woman had INH-resistant organisms. Her husband may have been infected before her organisms became resistant. Although only the woman has bacteriologically confirmed INH-resistant TB, there is a high probability that the four children with TB were infected with INH-resistant organisms. Therefore, they were placed on therapy with a combination of drugs to which the INH-resistant organisms are sensitive.
Since there is also a relatively high probability that reactors without disease have been infected with INH-resistant organisms, these individuals have been given rifampin as preventive therapy. Although the efficacy of preventive therapy with rifampin has not been demonstrated in controlled trials, the results of a study using the Delphi technique and decision analysis to determine the choice of preventive treatment for INH-resistant tuberculous infection support the use of rifampin (2). This outbreak is the largest in which rifampin has been used as an alternative regimen to prevent TB.
Another notable aspect of this outbreak is the large number of infected children, including four with TB and 25 reactors. This illustrates that TB in children is still a problem in this country.
A final aspect of this outbreak is the interstate transmission of tuberculous infection. Infected persons have been identified in four states; contacts have been identified in eight. Since transmission occurred across state lines, efficient communication between local, state, regional, and federal health authorities has been an essential part of efforts to control the outbreak.
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