What is it?
Tuberculosis (TB) is an infectious disease caused by
Mycobacterium tuberculosis bacteria. TB may affect many body organs but primarily targets the lungs. It is spread through the air from person to person through respiratory secretions such as
sputum or aerosols released by coughing, sneezing, laughing, or breathing. Most of those who become infected with
M. tuberculosis manage to confine the mycobacteria to a few cells in their body, where they stay alive but in an inactive form. This latent TB infection does not make the patient sick or infectious and, in most cases, it does not progress to active tuberculosis.
However, some patients - especially those with compromised immune systems - may progress directly from initial TB infection to active tuberculosis. In another 10% of those with latent TB infection that has not been treated, the mycobacteria will later be reactivated and begin to multiply - leading to active progressive tuberculosis disease.
TB has been a leading cause of death for thousands of years. In the days before the discovery of antibiotics it was called consumption, and those who contracted it were put into long-term hospitals called sanatoriums for the rest of their lives. In the early 1900s, more than 80% of the U.S. population was infected with TB, and tuberculosis was the single most common cause of death. Although its incidence has decreased dramatically in the United States, the World Health Organization (WHO) estimates that one-third of the world’s population is currently infected with M. tuberculosis and that a new person is infected every second. Worldwide, TB is still the leading cause of death due to infection, killing about 2 million people a year.
In the U.S., there are now about 10 to 15 million people with latent TB infection. Active TB was thought to be under control until a resurgence in new cases in the early 1990s. The majority of these new cases were among those living in overcrowded or confined populations such as correctional facilities, nursing homes, and schools. The most vulnerable were those who were medically underserved or had diseases and conditions that weakened their immune systems, such as: the homeless, alcoholics, intravenous drug users, those with HIV or AIDS, and those with chronic kidney or liver diseases. Often these new cases were multi-drug resistant (MDR), making them more difficult to treat. While the numbers of new cases of active TB have again declined in the U.S. due to constant vigilance by the medical community, TB remains a significant national and global public health concern.
Patients infected with both HIV and M. tuberculosis are a continuing concern. They have been shown to be at a significantly increased risk of developing active TB and of dying from it. Extensively drug-resistant tuberculosis (XDR TB) is an emerging concern. It is even more resistant and difficult to treat than MDR and has been recently defined by WHO and the Centers for Disease Control and Prevention as M. Tuberculosis that is resistant to the drugs isoniazid and rifampin, to the drug class fluoroquinolone, and to at least one of three injectable “second-line” drugs (amikacin, kanamycin, or capreomycin). Although still relatively rare, cases of XDR TB are being closely monitored by the world medical community and measures are being taken in hopes of limiting its spread.
On This Site