A chest x-ray from a person with tuberculosis (in right upper part of the photo.(

A chest X-ray from a person with tuberculosis (in right upper part of the photo).

by James Hubbard, MD, MPH

Lately I’ve had several interviewers ask me a question I haven’t been asked before: How contagious is tuberculosis? I’m guessing the reason is either the highly reported outbreak in a California classroom, a couple of publicized cases of multiple-drug resistant tuberculosis found in foreigners traveling here in the United States, or the news of camps of children—some reportedly with TB—at the U.S.-Mexican border.

But then, I should never be surprised that people would like to know about the risk of one of the oldest, deadliest, and still most worldwide prevalent diseases around. And since this could well be a deadly concern in disaster situations, I thought it a good subject to address.

Tuberculosis Truths
  1. In the early part of the 20th century, tuberculosis killed about one in seven Americans.
  2. In 2012, the latest year data is available, the CDC reports there were around 10,000 documented cases in the U.S.
  3. Over 500 people died of TB in 2012.
  4. If treated properly with the right antibiotics, tuberculosis is curable in most cases.
  5. The earlier treatment is started, the more likely the cure.
  6. The mortality rate for active TB, if untreated with antibiotics, is around 50 percent.
  7. In order to know the treatment, prognosis, and how contagious TB is, you first must learn the difference in latent and active TB.
Latent vs. Active Tuberculosis

Latent Tuberculosis

Ninety percent of people infected with tuberculosis have this type. When the infection gets into our lungs, our immune system is able to catch it early and wall it off completely. It’s sealed off so well that we’re not contagious. We have no symptoms, are not sick, and may never know we have it. But—and a big but it is—the bacteria aren’t killed and about 10 percent of the time, they are able to fight through this wall and cause active tuberculosis.




TB skin test


Latent TB is usually treated and cured with a couple of months or more of one to two rounds of antibiotics.

Active Tuberculosis

This is the bad stuff. It kills and it is contagious. About 5 percent of latent tuberculosis becomes active sometime between soon after you’re infected to the first two years of infection. Another 5 percent can become active anytime during a person’s lifetime.

People who have HIV or are alcoholics or drug abusers, and others with weak immune systems are more likely to get active TB. Smokers are also more likely to get it.

About 90 percent of people with active TB can be cured by taking a combination of several types of antibiotics for about 4–9 months. But, even with treatment, 10 percent will eventually die. Poor health or delayed treatment until the infection has caused more serious damage decreases odds of survival. Also, active tuberculosis can not only infect the lungs, it can get in bones, kidneys, and virtually anywhere in the body. If it’s already spread, about 25 percent of people will die despite treatment.

After about two weeks of adequate antibiotic treatment, you should no longer be contagious.

Since active TB is a killer, is contagious, and is harder to treat, it’s way better to diagnose and treat it when it’s latent. And that’s the reasoning for the TB skin test. Because, remember, latent TB causes no symptoms. Latent TB is usually treated and cured with a couple of months or more of one to two antibiotics.


Symptoms may include any of the following:

  • A prolonged cough lasting over three weeks
  • Bloody sputum (sputum is the secretion coughed up from the lungs)
  • Fever and chills
  • Night sweats
  • Poor appetite and weight loss
  • Chest pain

People can have one, many, or all of these symptoms. Some may have a little fatigue and nothing else.


  • Positive TB skin test
  • Evidence of infection on chest X-ray
  • The bacteria seen in the sputum under the microscope or cultured out


Treatment is with a combination of several antibiotics for anywhere from two to nine months. People with active TB should be isolated until treatment is well underway. A surgical mask worn by the infected person can decrease the spread of the bacteria. After about two weeks of adequate antibiotic treatment, the person should no longer be contagious.

More About Treatment and Prevention


Antibiotics used to treat TB are not the typical type you might have on hand for other infections. The most common ones are isoniazid, rifampin, rifapentine, ethambutol, and pyrazinamide in various sorts of combination. And, whether the treatment is for active or latent, it’s very important to take every dose.

What can be done other than antibiotics?

If you have the latent type, you’d do nothing except try to keep your immune system up with good nutrition, rest, no smoking, etc. If you have the active type, about all you can do is get rest, fresh air, and sunshine (there is some evidence that supplemental vitamin D helps), but without adequate antibiotics, about 50 percent or more will die from the disease.


The bacille Calmette-Guerinis, or BCG, vaccine is used in many countries that help prevent TB, especially in young children. It’s not used here in the United States a lot for various reasons including its questionable effectiveness, especially in adults.

Multidrug-Resistant Tuberculosis

Just like other bacterial infections, such a staph, some TB is resistant to the more common antibiotics used for it. This type is diagnosed by a culture of the infection that shows resistance to certain antibiotics.

Right now multiple drug-resistant tuberculosis (MDR-TB) accounts for a little over 1 percent of tuberculosis here in the United States. Many of the cases are found in people with HIV and from people traveling from overseas, especially Asia.

Treatment can take much longer, and the antibiotics used can cause more side effects than the ones used for common TB. The cure rate is only about 50 percent.

Extensively Drug-Resistant Tuberculosis

Also cropping up is what’s being called extensively drug-resistant tuberculosis (XDR-TB).  Right now, there are usually about 10 or fewer cases per year in the U.S., but much more in other countries. As you probably have figured out, it’s resistant to even more antibiotics, even harder to treat, and, more often than not, fatal.

Bottom Line

No matter what type of tuberculosis it is, eating nutritiously and not smoking keeps your resistance up, and helps you fight the disease if you get it. Also consider a vitamin D supplement. If there’s a chance you’ve been around a case of active TB, get a skin test.  The earlier you start treatment the better the odds of cure and the less you’ll spread the infection to other people.

What about you? Please share your experience if you’ve ever had a scare or had a positive skin test. Of if you or someone you know has ever been treated.


Photo: Flickr/JavierDevilman shared under CC BY-NC 2.0.