NBC News - The U.S. had the fewest cases of tuberculosis cases ever recorded last year, federal officials said Thursday.
But there are still far more cases than officials ever want to see — 9,412. And while the numbers go down a little every year, last year had the smallest decline since 1992, the Centers for Disease Control and Prevention says.
"What we have seen, actually, is good," said Dr. Philip LoBue, who heads CDC's tuberculosis division.
"That is the smallest number of cases since we started reporting in the 1950s."
But the numbers certainly are not plunging.
The U.S. has two sources of tuberculosis — people bringing it in from heavily affected countries, which means much of the rest of the world, and people living here who have latent infections that somehow become active infections.
"TB is a global problem. Unless the global problem is successfully addressed, it is going to affect the United States," LoBue said. Better testing has helped, however, the CDC says.
Globally, according to the World Health Organization, 9 million people became infected with TB in 2013 and 1.5 million died from it. About a third of the world's population has latent TB.
"It's probably easier to say the countries which have a low prevalence," said LoBue. They include the U.S., Canada, most of Western Europe, Australia, New Zealand and Japan.
Earlier this week, the European Center for Disease Prevention and Control reported 360,000 Europeans — that includes all of Europe — developed TB in 2013. Most U.S. cases come from countries with high levels of immigration, including China, the Philippines and Mexico.
Tuberculosis is caused by bacteria called Mycobacterium tuberculosis. It can cause an infection that doesn't make people sick until something happens that allows the bacteria to overwhelm the immune system.
"They feel well but they are at risk to progress to TB disease and become sick," LoBue told NBC News.
CDC estimates about 11 million people in the U.S. have latent TB. The latest batch — 27 students who tested positive for latent infection at a Kansas high school this week.
"Those people have a have 5 to 10 percent lifetime risk of going on to active tuberculosis," LoBue said.
It's expensive and inconvenient to treat active TB. "Any individual person who gets TB, it is a significant life event. They are going to be on treatment for six months," LoBue said.
"They have to be in respiratory isolation. They may not be able to work during that time. If they have drug-resistant TB they will be on treatment for longer — years or more."
It costs about $17,000 to treat normal, drug-susceptible TB. But there are strains of tuberculosis that resist antibiotics — they are called multiple drug-resistant (MDR) TB and those cases can cost $100,000 or more to treat.
The good news is that TB is not easy to catch. It requires sustained contact in rooms with little air circulation. Only about 30 percent of people who live with TB patients get infected themselves.