The Centers for Disease control is trying to track down anyone who may have come into contact with a woman who has a form of tuberculosis that is extremely resistant to drugs. That includes passengers who were with her on a flight. The woman is now being treated at the NIH outside Washington.
The female patient with extensively drug-resistant tuberculosis traveled from India to the U.S. through Chicago O'Hare Airport, arriving on April 4.
CBS News has learned she was diagnosed with the disease in India.
But is it known how long she had TB before coming to the United States?
"It's not just a matter of months," said Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases. "It's likely been a few years that she's had TB.
"She was treated in multiple places," he continued. "It became clear when they examined the bacteria that despite the fact that she had been and was being treated that in fact the microbe was resistant."
One problem: She didn't seek treatment until seven weeks after arriving in the U.S. Once she landed in Chicago, she traveled to Missouri and Tennessee before returning to Illinois for evaluation.
Since TB is spread through the air, federal health officials are contacting fellow passengers from her flight.
Still, how likely is it that anybody in the United States or in the airplane who was exposed to the patient will come down with TB?
"The risk is low, certainly not zero but low," said Fauci. "The risk is increased by the duration of the flight and by the proximity to the person in the plane."
There are about 200 times more cases of active TB in India than in the United States. In 2013, there were 2.6 million TB cases there, compared to 13,000 in the U.S., where XDR treatment success was 60 percent in 2011, compared to 22 percent worldwide.
The NIH has started to treat the patient, but it's too early to know which combination of drugs will be effective. The CDC says people with active TB are not supposed to fly and health officials are investigating whether she specifically came to the U.S. to be treated.