TB fight goes global with guidance for poor nations
Emphasis on identifying and separating TB cases
Though declining steadily in the United States, tuberculosis is taking a terrible toll globally that includes nosocomial spread to patients and health care workers in impoverished countries, public health officials warn. To meet the threat, the World Health Organization (WHO) in Geneva is distributing guidelines for the prevention of TB in health care facilities in resource-limited settings. Written in part by the Centers for Disease Control and Prevention, the guidelines essentially adapt the CDC’s 1994 guidance for U.S. facilities for health care facilities with few resources.1
"The United States and the CDC have the responsibility to work on TB from the global perspective because we can only affect the TB picture in the U.S. so much [by focusing on national controls]," says Patricia M. Simone, MD, one of the authors of the WHO guideline and chief of the field services branch in the CDC division of TB elimination.
Indeed, TB is the leading cause of mortality among adults in the world, killing some 2 million people annually. Overall, approximately 1 billion people are infected, the vast majority of them in countries with limited health care resources. Moreover, even as TB has declined steadily in the United States, the proportion of cases occurring in foreign-born people has increased steadily since the mid-1980s, reaching 42% in 1998. Because it appears that TB cases among foreign-born people residing in the United States could soon outnumber cases among U.S.-born people, the CDC and its advisors have concluded that TB elimination in the United States will not be possible without a substantial reduction in the global TB burden.
"It varies quite a bit, but the main problem in the low-income countries is that they have large wards of patients, many of whom have symptoms that could be TB," Simone says. "They also have a lot of HIV-infected patients in these countries. The other big problem is there may not be a rapid ability to diagnosis patients, so there will be wards with patients who have TB [mixed with] those who don’t."
Directly observed therapy
The guidelines underscore that administration of standard short-course chemotherapy under direct observation by health care workers will cure most TB patients. However, recent studies performed in developing countries have shown that health care workers caring for infectious TB patients are at increased risk of infection and disease. Health care workers are essential in the fight against TB, and they should be protected, the document emphasizes, citing nosocomial transmission cases in health settings in Africa, Thailand, and Brazil.2-4
The greatest threat to workers is the undiagnosed and untreated patient. "The data certainly point to nosocomial transmission happening in these settings," Simone says. "It’s hard to really say for sure without DNA fingerprinting studies. It’s possible that some community transmission is occurring, because there is high prevalence of TB in these communities as well."
As a practical approach to the TB problem, the guidelines recommend trying to separate patients into three areas of the health care facility: those with confirmed TB, those with suspected TB, and those who have been ruled out for TB. "Those in whom TB is ruled out can be on the general medicine ward," she says.
But because the use of respirators and corresponding respiratory fit-testing programs are impractical in such settings, the guidelines give primary emphasis to identification, "separation," and treatment of patients. For example, facilities in some countries designate "cough officers" to identify and triage the obviously symptomatic cases in common waiting areas.
"The same principles apply," she says. "The highest priority are administrative controls, which emphasize early recognition of tuberculosis or suspected TB. In the CDC guidelines, we talk a lot about isolation [in terms] of mechanical, ventilated isolation in which the air is actually [under negative pressure vented to the outside]. In these guidelines, we talk more about separation, which is just putting people in a separate place so they are separated by distance to reduce the transmission."
In the absence of engineering controls, the guidelines suggest common-sense measures like opening windows, using fans, and doing sputum induction outside. "The risk of transmission depends on the concentration of droplet nuclei in the air," she says. "[That] can be reduced either by reducing the amount of droplet nuclei generated into the air — by either putting a mask on the patient or treating the patient so they don’t cough infectious germs — or by separating the patient so they can’t cough the germs into the air that everybody else is breathing."
In addition, surgical masks may prevent the spread of microorganisms from a TB patient but do not provide protection to health care workers. Workers may mask in such settings to achieve some limited protection, but they are not as protected as they would be by respirators, she says. "Putting a mask on a [TB] patient is an easy cheap way to reduce — but not eliminate — the number of droplet nuclei in the air," Simone adds. While respirators protect the wearer from inhaling infectious droplet nuclei, they are expensive and should be reserved for high-risk referral hospital settings, the guidelines recommend.
"We have very limited recommendations for [respirators] in this document, because you can’t really implement a respiratory protection program if you don’t have the administrative controls in place and you don’t really have the isolation rooms," she says. "[If] the air can go either way across the door, for example, then it doesn’t make sense for a health care worker to wear a respirator in the room and not outside the room."
(Editor’s note: The WHO TB guidelines are available at http://who.int/gtb/publications/healthcare/ PDF/WHO99-269.pdf.)
1. Granich R, Binkin NJ, Jarvis WR, et al. Guidelines for the prevention of tuberculosis in health care facilities in resource-limited settings. Geneva; World Health Organization, 1999.
2. Wilkinson D, Crump J, Pillay M, Sturm AW. Nosocomial transmission of tuberculosis in Africa documented by restriction fragment length polymorphism. Trans R Soc Trop Med Hyg 1997; 91:318.
3. Muzzy de Souza GR, Cravo R, Figuueira MM, et al. Tuberculin conversion among health care workers in a general hospital of Rio de Janeiro, Brazil. Final results. Am J Respir Crit Care Med 1998; 157:705.
4. Do AN, Limpakarnjarat W, Urhaivoravit PLF, et al. Increased risk of Mycobacterium tuberculosis infection related to the occupational exposures of health care workers in Chiang Rai, Thailand. Int J Tuberc Lung Dis 1999; 3:377-381.