If someone has an active case of tuberculosis he or she has to be isolated for the sake of the public’s health.

A young man in Georgia was told Friday he has tuberculosis and didn’t believe it, so he started to walk out to go back to his house and then to Mexico.

Friday evening the young man was put into a special isolation cell in the jail where he has a ventilation system that does not allow the air from his cell to circulate into the rest of the jail.

Good move, especially after the last case a couple of months ago.

When doctors told Francisco Santos he had tuberculosis Friday, health officials said the Gwinnett County 17-year-old refused to believe it.

Then the wiry, dark-haired youth refused to submit to any treatment. Worse, he said he was walking out of the Gwinnett Medical Center in Lawrenceville and heading back to his home country of Mexico, officials said.

Francisco Santos lives in Norcross with at least one parent and several younger siblings, records show.

“I think he was scared,” said David Will, attorney for the Gwinnett County Board of Health.

Gwinnett health officials found themselves in a bind. They had a person with a case of active, contagious tuberculosis, refusing treatment and threatening to carry the disease to a foreign country.

They also were aware of the recent incident involving Atlanta lawyer Andrew Speaker, who also has tuberculosis. After Speaker left for his wedding in Greece, a national news conference set off an international health scare.

In this case, the Gwinnett officials acted decisively: They put Santos in jail Friday evening, in a rare act of a government agency confining a sick person. Santos is the only inmate in a special medical isolation cell designed for inmates with contagious conditions. The cell, which measures about 15 feet by 20 feet, has a special ventilation system that keeps the air from reaching other inmates.

The 5-foot-5 teenager has a toilet, sink, bed and a mirror made of polished metal. Two deputies guard him and the other medical inmates.

Will, the county health attorney, said Santos was detained because he is a public health threat.

“He has active, contagious TB,” Will said Saturday. “He is at risk of communicating that with anybody he comes in contact with.”

Will said Santos is being held under a court order for confinement. He’ll stay in that cell until either he starts cooperating and accepting treatment, or a judge makes some other decision at a Sept. 5 hearing. At that commitment hearing, the judge could decide to place him in a hospital with security.