CHICAGO (AP) – The Rev. Jesse Jackson visited the Cook County Jail on Friday, where he took an HIV test and encouraged inmates to do the same.

“You can help us attack a killer disease before a killer disease kills us,” Jackson told the crowd of inmates, before dozens lined up to take the tests that involved rubbing a swab along the gum line above their upper teeth.

Jackson’s appearance comes at a time when lawmakers across the country are pushing or considering legislation to require mandatory testing of inmates for HIV, the virus that causes AIDS. Several states have taken up such measures, and U.S. Rep. Maxine Waters, D-Calif., is expected to introduce a bill that would require HIV testing of inmates when they enter and leave federal prison.

Illinois law requires that inmates be offered HIV tests when they arrive at a state prison and before their release, but those tests are voluntary, said Derek Schnapp, a spokesperson for the state’s corrections department.

Jackson said it is unclear how widespread HIV is in jails. But if even a fraction of the 14,000 inmates housed at the Cook County Jail every year and the tens of thousands jailed around the country are infected, they pose a substantial health risk to the public.

He said some inmates may unknowingly be infected before they enter jail, or may become infected if they engage in sex while in jail. That puts other inmates at risk as well as people they have sex with when they are released, he said.

“We have the power to stop spreading HIV,” he said. “We have the power to stop spreading death.”

He also told inmates that if the tests were positive, they could get lifesaving drugs, and assured them only they would know the results. Jail officials said the test is painless and the preliminary results can be known in a matter of minutes.

“You don’t have to take this test but you ought to take it,” Jackson told the inmates.