Officials at the Fairfax County Health Department in Virginia are investigating a tuberculosis outbreak at a Virginia high school that has infected three people.
The health department officials said 430 faculty members and students might have been exposed and need to be tested for the disease.
The health department originally opened and completed an investigation at the school in December, when one person was diagnosed. But the case was reopened after two additional people at the same school - Robert E. Lee High School in Springfield - were found to have contracted tuberculosis.
The health department investigation has not concluded that the cases are related and did not specify whether the infected where students or staff, who ended the school year Tuesday.
Tuberculosis is caused by bacteria that usually attacks the lungs and is potentially fatal. The disease is spread when an infected person expels the bacteria into the air and it enters the lungs of another person. The bacteria can linger in the air for hours after being expelled, according to the Centers for Disease Control and Prevention.
Symptoms of tuberculosis include fever, chills and coughing up of blood.
Tuberculosis is usually treated with six months of antibiotics, but new strains of the disease have become resistant to medication, according to the World Health Organization (WHO).
The WHO estimates that 5 percent of tuberculosis cases are multidrug resistant tuberculosis (MDR TB) or virulent strains that do not respond to the primary antibiotics given to treat the disease. There were 98 cases of MDR TB in the United States in 2011, the year for which the most recent data is available.
There were 10, 528 diagnosed cases of tuberculosis in the U.S. in 2011.
Officials at the Fairfax County Health Department did not specify whether the tuberculosis strains were MDR TB.
About 1.34 million people die worldwide every year from tuberculosis, according to the WHO.