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Extensively Drug Resistant: What is XDR TB?

by Maggie Fox /  / Updated 

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A woman who traveled from India is being treated at the National Institutes of Health for an almost impossible to cure form of tuberculosis called XDR TB. Here are answers to five top questions about the infection.

What’s the risk to me?

Very low. Tuberculosis is very common globally, but there are only about 9,000 new cases a year in the U.S. XDR-TB is very rare in the U.S. CDC says it got reports of 63 cases between 1993 and 2011. It’s a dangerous and hard-to-treat infection but it’s not any easier to transmit than normal TB. Even though tuberculosis infects millions, it requires extended close contact to catch it. You can’t catch it by kissing, sharing a toothbrush, sitting next to someone or touching something they've touched. People most at risk are patients with HIV and people with suppressed immune systems from, for instance, cancer treatment.

What does XDR mean?

XDR TB stands for extensively drug resistant tuberculosis. TB is difficult to treat to start with, requiring weeks or even months of antibiotics to clear it. Like all bacteria, the tuberculosis bacillus evolves and mutates to resist the effects of drugs. There’s also a form called multiple drug-resistant TB, or MDR TB, which is bad enough. XDR TB resists several classes of drugs and patients may require two years of therapy, as well as surgery, to clear the infection.

Does that mean it’s more dangerous?

It’s more dangerous to people who have it. XDR TB developed because it’s very difficult for people to finish the long and often unpleasant treatment course to clear up TB. When treatment fails to completely eradicate an infection, the bacteria that remain are often better able to resist the antibiotics. They can naturally develop this resistance or they can swap genes with bacteria that are resistant. Only about 30 to 50 percent of patients with XDR TB can be cured.

What are the symptoms?

They’re the same as for any TB infection: Feeling sick or weak, weight loss, night sweats, fever, coughing, coughing up blood, and chest pain. Symptoms of TB disease in other parts of the body depend on the area affected. Most people with TB have a latent form that has no symptoms at all. About one-third of the world's population has latent TB. They cannot infect anyone else but if something happens to their immune system, the TB can become active.

How long does it take to find out if you have XDR TB?

There is no on-the-spot test for TB but it’s pretty quick if you have active lung disease and the bacteria are in your sputum or phlegm. There’s a skin test for TB, but it requires specialized testing to see if a person has multiple drug resistant (MDR) or extensively drug resistant (XDR) TB. The bacteria must be grown in culture and tests and that can take weeks or even months.

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