Public health officials have launched a new, coordinated effort to contain a persistent outbreak of tuberculosis in downtown L.A.’s skid row, including searching for more than 4,500 people who may have been exposed to the disease.

The Centers for Disease Control and Prevention have dispatched scientists to Los Angeles to help local health officials figure out why the disease is spreading and how to stop it.

Nearly 80 tuberculosis cases have been identified and 11 people have died since 2007, most of them homeless people who live in and around skid row.

Scientists have recently linked the outbreak to one tuberculosis strain that is unique to Los Angeles, with a few isolated cases outside the area.

“This is the largest outbreak in a decade,” said Jonathan Fielding, director of the Los Angeles County Department of Public Health. “We are really putting all of our resources into this.”

Health workers have identified about 4,650 people who probably were exposed and are trying to track them down for testing and treatment. Local and federal officials are particularly concerned because the cases are all linked to one relatively small geographic area and one vulnerable population. Officials are worried the outbreak could spread beyond skid row if action isn’t taken.

Homeless people are especially at risk of getting tuberculosis and of being undiagnosed because they tend to have poor hygiene and nutrition, limited access to healthcare and ongoing contact with infected people. Transmission of the airborne disease is also common because they tend to live in overcrowded areas and to continually move among hospitals, shelters and the streets. Many homeless people also have substance abuse or mental health issues that can impede treatment.

“They go from place to place and the likelihood of passing it along is much greater,” said Paul Gregerson, chief medical officer of the JWCH Institute, which runs a homeless healthcare program on skid row. “It makes everybody more susceptible.”

Tuberculosis is easily passed along. It is contracted by inhaling droplets from infected patients when they sneeze, cough or laugh. When left untreated, the disease can be deadly. The skid row strain can be treated by all anti-TB medications. Treatment lasts six to nine months.