The new tuberculosis.

Despite the fact that there are 8 million new cases of tuberculosis (TB) annually and 3 million deaths TB has been a neglected public health priority primarily because effective chemotherapy has led to a dramatic decrease in cases in industrialized countries and most cases in developing countries occur in adults. It has only been recently that the emergence of multi-drug resistant TB and the rapid disease progression in HIV-infected persons has led to the application of the methods of modern basic science to TB. Population movement among refugees and immigrants and the neglect of the public health infrastructure have also led to increases in the number of cases worldwide. TB and HIV interact in 4 ways: TB may become reactivated in an HIV-infected person; there may be a primary TB infection an HIV-positive person may suffer reinfection; or TB may alter the natural history of the HIV infection. In developing countries the TB seen in association with HIV is believed to be reactivation of latent infection. HIV seropositivity is associated with a 30-50% lifetime risk of TB as compared with a 10% risk in the uninfected. Reactivation of TB in HIV positive people causes an additional 250000 cases in Africa each year. HIV changes the course of TB; first time exposure is associated with 30-40% attack rates short incubation periods and rapid progression of the disease. It is also suggested that TB may hasten the progression of HIV although this has not been proved. HIV-associated cases of TB will continue to increase in Africa but in the future the largest number of co-infected persons will be in Asia. The clinical manifestations of HIV-related TB become more severe according to the progression of the immunodeficiency. Patients dying of AIDS who also have TB usually have extremely heavy mycobacterial burdens with widespread probably incurable TB. Being HIV-positive is also associated more often with sputum-negative pulmonary or extrapulmonary TB and with atypical radiological manifestations such as absence of cavitation absence of localization to the upper zones and the presence of hilar adenopathy effusions or infiltrates. Diagnosis may therefore be more difficult in cases of HIV infection. Although a greater mortality is found in HIV-positive patients (perhaps associated with complications of other bacterial infections) TB can be treated successfully in HIV-infected people. The World Health Organization recommends short-course chemotherapy of isoniazid rifampicin ethambutol and pyrazinamind for 2 months followed by 4 months of isoiazid and rifampicin or 6 months of isoniazid and ethambutol. The risk of recurrence is greater if non-rifampicin regimens are used and is 3-34 times greater than in seronegative cases. Treatment is complicated by the fact that 18-20% of HIV-positive people have adverse reactions to thiacetazone which presents as a skin condition and can lead to death. Proposed solutions to this problem are to replace thiacetazone with another drug replace thiacetazone only in HIV-positive persons (testing all patients for HIV) or educating staff and patients about the need to discontinue the drug if a rash occurs. Donor funding will be necessary to adopt a single worldwide approach with the least side effects. Policy decisions must also be made to create a programmatic approach to preventing HIV-associated TB.