While most of us may not know of an active case of tuberculosis in our own circle, to say it is still a global health problem would be putting it mildly. The National Institute of Allergy and Infectious Disease estimates that up to a third of the world’s population may be infected with mycobacterium tuberculosis and that 10 million new cases are diagnosed each year. Additionally, the Center for Disease Control (CDC) states that there is a 5-10 percent lifetime risk of progression from inactive to active disease. Certainly this is no goodbye to tuberculosis prevalence.
While the incidence is far less, percentage-wise, in developed countries such as the United States, a 15 percent increase in occurrence was reported to the CDC during the HIV epidemic of the late 80s and early 90s. The incidence still is significant in the general population due to immigration to the United States from high-incidence countries, from illicit drug use, and among those in the rapidly expanding health care field. People who have inactive or latent tuberculosis generally don’t feel ill, so the only evidence of infection is a positive screening test, often during an application for employment or as part of school screening.
Tuberculosis enters the body primarily through the lungs. Therefore, the lungs are the major site of infection, although tuberculosis can exist in the bones, lymph nodes, and virtually any place in the body. As mentioned, it usually exists in a dormant or latent form. When progressive, constitutional symptoms such as weight loss, fever, night sweats and malaise occur. Chronic cough is the most common pulmonary symptom. Blood in the sputum can be a more advanced sign, and on physical examination chronic illness is very apparent.
One problem in eradicating tuberculosis is erratic standards for diagnosing the disease. Cost containment often limits testing to high risk populations and is not offered to those likely to refuse treatment. A positive tuberculosis skin test indicates exposure to the disease, but the risk of treatment and side effects often exceeds the potential benefit in older individuals and those who have not converted from negative to positive in a recent time frame. Tuberculosis is proved by isolating the bacillus, and a chest x-ray, sputum and culture confirm the diagnosis.
Once discovered, tuberculosis should be treated immediately. Isoniazid (INH) is the primary drug of choice, and as the disease is a tough one to eradicate often requires between six and nine months of continuous treatment. Many other medications have been developed, and unfortunately, strains of drug-resistant disease have emerged. The toughest cases are those in people who are immunosuppressed (such as from HIV infection) and the elderly, where reactivation occurs after many years of dormancy and the immune system isn’t as active as at younger ages in fighting the disease. Treatment failure occurs not infrequently since most do not keep up taking the medication for the long period necessary to completely inactivate the disease.
Most cases of completely treated disease or positive skin testing with no evidence of active infection can be issued at standard. Preferred status is reserved for those with follow-up testing that shows no evidence of disease and no history of any immune system disorder. Those with active disease or who are in the midst of treatment are generally postponed.
Resources:
Centers for Disease Control and Prevention (CDC). Recommendations for use of an isoniazid-rifampin regimen with direct observation to treat latent Mycobacterium tuberculosis infection. MMWR Morb Mortal Wkly Rep. 2011; 60(48): 1650-53.
National Institute of Allergy and Infectious Diseases. Tuberculosis (Tb). www.niaid.nih.gov/topics/tuberculosis/Understanding/Pages/overview.aspx.
