Dear Doctors: I was surprised when I had to have a TB test for a new job and was shocked that it came back positive. I have no symptoms, and I feel fine. How do you get it? Could I have infected my family? I never realized that TB is common enough in the United States to automatically have to test for it.
Dear Reader: Tuberculosis, or TB, is a disease caused by a bacterium known as Mycobacterium tuberculosis. When someone with an active infection coughs, sneezes or shouts, they release minute bits of moisture known as “droplet nuclei,” which contain the bacterium. These droplets are tiny enough that they can drift on an air current, move throughout a room and remain suspended for several hours. This makes the disease highly infectious. If someone inhales these droplets, the TB bacteria they contain can reach the lungs, a friendly environment in which they can begin to grow. They can also settle in the lymph nodes and cause tuberculosis of the throat.
Symptoms of TB include fever, weight loss, night sweats and a wet cough that may produce bloody phlegm. If an active TB infection goes untreated, the bacterium can travel via the bloodstream and infect other tissues, including the kidneys, spine or brain.
When someone tests positive for TB but has no symptoms, as in your case, this is known as latent TB. It means that while the bacterium is in your body, it is a small amount and not yet making you ill.
Someone with latent TB is not infectious. They cannot pass along the disease. However, in some people, latent TB will transition to an active infection, which is known as TB disease. This can take up to two or more years. For that reason, anyone with latent TB should undergo treatment with antibiotics to eliminate the bacterium from the body.
Tuberculosis is a serious international health threat. Worldwide, up to 10 million people develop an active TB infection each year, and 1.5 million die.
In the U.S., thanks to vigilant testing and treatment, the disease isn’t as prevalent. But this wasn’t always the case. At the start of the 20th century, TB was a leading cause of death in the United States. Historical reports from that time place the number at more than 150,000 deaths a year from TB.
Thanks to intensive efforts at detection, treatment and prevention, along with development of the antibiotic streptomycin in 1943, the U.S has been able to turn the tide. According to the Centers for Disease Control and Prevention, the U.S. saw 7,800 active TB infections last year, and about 500 deaths. Keeping these numbers low is the reason that many employers require a TB test.
Unfortunately, despite this remarkable turnaround, significant challenges remain. This includes the rise of drug-resistant strains of the bacterium, which are not affected by isoniazid and rifampin, the primary antibiotics used to fight the disease. All of this makes it important for you to seek immediate medical care for your latent TB infection, and to complete the course of medications exactly as prescribed.
(Send your questions to [email protected], or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)