Updated

California health officials are tracking a new tuberculosis strain that has emerged in an area of downtown Los Angeles frequented by a large concentration of homeless people.

Homeless shelters in Skid Row are increasing efforts to urge people to get tested after state and local public health officials alerted them to the outbreak earlier this month.

The U.S. Centers for Disease Control and Prevention will be sending a team of specialists to Los Angeles next month to investigate the causes and spread of the often lethal lung infection, spokeswoman Salina Cranor said.

Tuberculosis is a highly contagious disease spread by airborne contact such as coughing, sneezing and spitting. It is often seen in environments where people live in crowded quarters, such as in prisons and homeless shelters.

It has long been a problem in Skid Row, a 50-square-block area that houses the nation's densest concentration of homeless people. About 1,000 people sleep on sidewalks nightly, and several thousand more seek refuge in four shelters.

Employees at the shelters are already routinely tested for TB and some also test clients, but several shelters have increased outreach in light of the new outbreak.

"We're watching out for coughs and going out on the street looking for people coughing," said Andy Bales, president and chief executive of the Union Rescue Mission. "It's not a panic, but a plan to address a very persistent problem."

Several people have died of TB at the mission over the past year, he said.

The Los Angeles Mission is also expanding efforts to alert more homeless people about coughs as they come into the shelter, said Herb Smith, its president.

The Los Angeles Mission has provided health officials with a list of clients dating back to 2007. Officials are combing through the list to find the names of infected people and determine who stayed there at the same time, Smith said.

Finding people, however, is problematic as many homeless people have a transient lifestyle, moving among different areas of the city or to different cities. Even getting people to return to determine the result of a TB test is not easy, he noted.

News of the TB outbreak spread around Skid Row on Friday. Residents said it was worrisome because many people in Skid Row suffer from poor health and many people have been incarcerated, where they could have been exposed to TB. The disease can remain latent for some time.

"It don't take much for somebody to walk by and cough on you," said Bill Cannady, 52, adding that he has glaucoma and cataracts. "A little cough could be detrimental."