Health and school officials said the disease was diagnosed this month in two students at the Springfield high school after an initial case was discovered in December.
Gloria Addo-Ayensu, the county’s health director, said her department decided to conduct a broad investigation because three cases were found at Lee High School within six months. Officials said the investigation could determine whether there are undiagnosed cases among students and the staff.
Barbara Andrino, a doctor who specializes in tuberculosis for the Health Department, said tuberculosis can move between people by way of droplets that contain bacteria. “An individual contracts tuberculosis by breathing bacteria in the air,” she said.
Typical symptoms include a persistent cough, possibly with excessive mucus or blood.
Addo-Ayensu said about 90 tuberculosis cases were identified in the county last year.
According to the Virginia Health Department, the rate of tuberculosis infection has declined in the county since 2008, when 98 cases were identified. About 235 cases were reported statewide in 2012, and fewer than 30 cases involved people 24 or younger. Across the nation, fewer than 10,000 cases were diagnosed last year.
Most tuberculosis cases in Fairfax County — which has a diverse population that includes immigrant families from around the world — originate overseas, Addo-Ayensu said.
Principal Abe Jeffers said tuberculosis tests for the Lee High community would be available in the school gym Friday and early next week.
The school system sent a letter to 1,900 families in the Lee High community Monday about the three confirmed cases of tuberculosis. An additional 430 letters were sent to families of students and staff members whom the county Health Department had determined were at increased risk of exposure.
Addo-Ayensu said most tuberculosis cases in the county are highly treatable and do not involve more dangerous strains of the disease that are resistant to antibiotics.