Tuberculosis may have taken hold in downtown LA and experts fear that the outbreak could spread.

The CDC has launched a coordinated effort to screen as many people as possible to head off this easily spread bacterial infection. They want to know how and why the disease is spreading.

They do know that the spread is limited because the strain is unique to Los Angeles. But because this is the largest outbreak in a decade health care professionals are worried.

Officials have said that 11 people have died in the area from TB since 2007 and 80 have been identified as having been infected. Most of the people found infected were homeless and resided on skid row. Health officials think that up to 4,500 people may have been exposed.

"They go from place to place and the likelihood of passing it along is much greater," said Paul Gregerson, who was interviewed by the LA times and is chief medical officer of the JWCH Institute, which runs a homeless health care program on skid row. "It makes everybody more susceptible."

TB is spread by a hearty bacterium, Mycobacterium tuberculosis, which can live inside immune cells for years. The illness can cause severe degradation of the lungs and bloody coughing episodes. It only takes a few individual bacterial cells inhaled from another person's cough or sneeze to become infected.

The only way to treat Tuberculosis is with intensive antibiotic therapy that takes 6 to 9 months to complete. There is a close to 100-year-old vaccine that is given all over the world, but it is not too effective and new, more effective vaccines are being developed.

Without treatment, TB is usually fatal.

Information on TB can be found on the CDC website here.