The Miami-Dade Animal Services shelter in Medley remains closed for dog adoptions and surrenders because of an infectious disease outbreak that had affected 30 dogs by Tuesday.

Cat adoptions and surrenders aren’t affected.

The shelter closed its doors to dogs on Saturday after distemper, an incurable disease spread through the air, was detected. Eighteen shelter residents and one dog from the community that originated at the shelter have been euthanized.

Animal Services is offering free distemper testing through Saturday for dogs adopted from the shelter between Dec. 24, 2011 and Jan. 6, 2012. Testing is available from 10 a.m.-3 p.m. at the shelter, 7401 NW 74th St., no appointment necessary. Call 311 in Miami-Dade for more information.

Kathleen Labrada, the department’s enforcement manager, said that blood and cultures from seven dogs newly showing symptoms were sent to a lab on Tuesday.

“We don’t yet know if it’s an upper respiratory infection of the early stages of distemper,’’ she said. Depending on the results of those tests, expected Wednesday, the shelter could soon see a “modified reopening,’’ she said.