Tuberculosis (TB) is a major public health problem both in the United States and worldwide. After 30 years of a declining incidence of new cases, in 1985 the number of new cases of TB began to increase in the United States; from 1985 to 1991, there was an 18 percent increase in the number of new cases. The greatest increases have occurred among young adult African Americans and Hispanics living in large cities. Increases have been noted among persons who are infected with the human immunodeficiency virus (HIV), many of whom are injection drug users. The increase in new cases is occurring primarily in areas with high rates of HIV/AIDS, i.e., urban areas with a large, poor, minority population. The rise in new cases of TB is closely linked to the HIV epidemic. In addition, an increase in outbreaks of TB in a variety of settings (correctional facilities, homeless shelters, nursing homes, hospitals, drug treatment centers) is also contributing to the increase of TB.
Major outbreaks of HIV-related TB involving transmission of multidrug-resistant organisms have been recently reported - reports that are alarming to the public health and medical communities. Multidrug-resistant tuberculosis (MDR-TB) is defined as a tuberculosis infection in which the TB isolate is at least resistant to isoniazid and rifampin, the best available anti-TB drugs. From 1990 through early 1992, the Centers for Disease Control and Prevention (CDC), in collaboration with State and local health departments, investigated outbreaks of MDR-TB in hospitals and correctional facilities in Florida and New York. More than 200 cases of MDR-TB have been identified through these investigations. In these outbreaks, a number of health care workers exposed to patients with MDR-TB have been diagnosed with active disease or have converted their tuberculin skin tests from negative to positive. MDR-TB progresses rapidly in HIV-positive patients, with from 72percent to89 percent dying within 4 to 16 weeks.
Without aggressive screening and prevention measures, patients and staff in drug treatment centers are at substantial risk of developing active TB and, in some geographic areas, MDR-TB. Drug treatment programs can undertake a number of measures that will reduce this risk. Lessons learned from the MDR-TB outbreak - as well as the recommendations of CDC - provide a guide on what drug treatment programs can do to prevent transmission of both TB and MDR-TB among their patients and staff.
Characteristics of the MDR-TB Outbreaks
How did multidrug-resistant tuberculosis develop? Multiple reasons account for the increased incidence of MDR-TB, but several factors warrant comment. Drug resistance has developed primarily as a result of noncompliance with prescribed anti-TB therapy among patients with active tuberculosis. Many patients were started on appropriate therapy, but adequate and complete medical followup did not occur. Such followup must be consistently carried out to ensure ongoing compliance, completion of therapy, and successful outcomes. Failure to do this left many persons in the community with partially and unsuccessfully treated TB. This unsuccessfully treated population became the source of MDR-TB.
A second factor has been the failure of health care workers to suspect a case of active tuberculosis and rapidly isolate infectious TB patients. Patients who are not recognized as having active TB may expose other persons to the disease both in the hospital and in the community. Among HIV-infected persons, the consequences of failing to recognize possible exposure or active disease have been devastating. In addition, the absence of proper ventilation on hospital wards and in outpatient facilities, as well as in any of a number of other care facilities, has led to the spread of TB in hospitals, prisons, homeless shelters, and other settings.
Delay in Diagnosis
Prompt diagnosis of TB was not always made in the initial MDR-TB outbreaks, because the majority of persons with MDR-TB were HIV-positive, and many had AIDS. The clinical presentation of TB in this population is frequently atypical: lung cavitation may not be present on chest radiographs, and sputums may not be smear-positive for acid-fast bacilli.
In addition, the diagnosis was frequently based only on TB sputum culture results. In most cases, at least 8 weeks had elapsed before culture results were obtained, and even more time had elapsed before drug-susceptibility results became available. Thus even when treatment for TB was started, it usually did not include adequate drugs.
Inadequate Isolation Practices
Patients were not effectively isolated in health care settings. In many cases, doors to rooms of patients known to be infected with TB were not kept closed, health care workers and visitors did not wear masks or used masks improperly, and patients left their rooms without wearing masks. Many hospital isolation rooms did not have negative pressure relative to the hallways (i.e., the direction of air flow was from the isolation room to the hall. The airflow must be from the hall to the isolation room and then outside).
In addition, many HIV-infected persons were clustered on one ward or in large multibed rooms, and the infection was spread from patient to patient in the hospital.
Exposure of Health Care Workers
Because of the failure to recognize, isolate, and adequately treat these MDR - TB cases, a substantial number of health care workers and prison guards who were exposed converted their tuberculin skin tests, indicating recent infection with TB. At least nine of these workers have developed active MDR - TB, and five of them have died.
Prevention Efforts in Health Care Settings
The health care community is now charged with a series of critical tasks, including
- Limiting the spread of TB
- Screening for TB
- Educating the public about TB
- Developing improved strategies for earlier recognition of infection
- Providing supervised and appropriate care
- Making scientific advances that will enable earlier diagnosis as well as better therapies or vaccines
The Centers for Disease Control and Prevention has established guidelines for preventing the transmission of tuberculosis in health care settings. CDC guidelines are shown in table 1 . It is mandatory that drug treatment programs become familiar with these guidelines and implement them as necessary in their facilities. Health care facilities unable to comply with these guidelines should transfer any persons with suspected or active tuberculosis to an appropriate health care setting.
Public Health Issues and Implications for the Future
The public health policy regarding diagnosis, isolation, and treatment of tuberculosis in the United States - both now and for the foreseeable future - is undergoing increasing scrutiny and reevaluation. New guidelines are being developed, and over the next few years the approach to issues concerning TB will be changing. There are a number of issues that must be addressed and dealt with at a national level. The following improvements are needed:
- Improved screening methods to detect persons with latent or active TB
- More rapid laboratory diagnosis of active TB
- More rapid drug susceptibility testing to facilitate the prescribing of the most effective combination therapies
- Development of new anti-tuberculosis drugs
- Development of vaccines
- Provision of the means to isolate persons with active tuberculosis who are in health care facilities or other congregate settings (such as correctional facilities) until drug-susceptibility test results are available and until appropriate therapy has been administered for a sufficient period of time to eliminate infectivity
- Provision of the means to ensure prompt treatment with appropriate therapy given in a supervised setting
- Identification of better and/or shorter courses of therapy for preventive therapy of persons with latent infection (i.e., those with a positive purified protein derivative (PPD) or who are infected but are anergic)
- Improved environmental methods to protect potentially exposed persons in living and work places where exposure is of concern
- Better contact tracing and followup
- Education to improve awareness of TB in both health care workers and the general public
- Possible reopening of TB sanitoriums for infected persons for whom adequate and complete therapy will be otherwise difficult.
To limit the spread of MDR-TB and to protect both at-risk patients and health care providers, it is essential that the medical community undertake a concerted and determined campaign to limit the spread of TB, including MDR-TB, as well as HIV infection. This mandate will be one of the principal public health policy challenges for this country during the 1990s.
Substance Abuse and Mental Health Services Administration (US), Rockville (MD)
Center for Substance Abuse Treatment. Screening for Infectious Diseases Among Substance Abusers. Rockville (MD): Substance Abuse and Mental Health Services Administration (US); 1993. (Treatment Improvement Protocol (TIP) Series, No. 6.) Chapter 6 - Summary Statement on Tuberculosis.