As Austin tries to track down those who’ve come in contact with the 502 people who have tested positive for the coronavirus, the interim health authority and public health medical director said it’s hard to draw a clear line between many of the cases.

“In most circumstances, the relationship to another case is not known,” Dr. Mark Escott told Austin City Council members at their work session Tuesday. “That makes [isolating this disease] challenging.”

But the city has been able to identify eight clusters, or groups of infected people where they know how the disease was contracted. These include clusters at nursing homes and out-patient care centers, Escott said, although he said he could not publicly release the locations.

The ability to test others when a cluster is identified at a nursing home is limited, he said, because of the availability of the tests.

"We have tested the individuals that are living in that same hallway [as someone who is symptomatic and tested], for instance, as well as the staff,” Escott said. “We do not have enough tests to test everybody in every nursing home that has a case.”

Another cluster includes the 70 UT Austin students who traveled to Cabo San Lucas, Mexico, in mid-March for spring break. Last week, 44 of those 70 students had tested positive for COVID-19.

“They are acting very, very responsibly since their exposure. They have all quarantined themselves,” Escott said. “All of them are interested in being plasma donors to help those who are sick.”

Escott said he and his staff continue to be confounded by the virus and the fact that some patients who test positive show no symptoms. He said of 19 infected UT students he spoke with, only one had developed a fever.

“It’s puzzling us right now why there’s so much difference in clinical presentations and severity,” he said.

When council members pressed him on the city’s ability to test more people, Escott said he is hopeful that more testing kits, including "rapid" tests that could provide results in 15 minutes, would be available “in the near future.”

“Once we have that available in this community, it will really change the face of our ability to control this by providing rapid results,” Escott said, although he could not give council members an exact timeline on when additional test kits would be available.

Got a tip? Email Audrey McGlinchy at audrey@kut.org. Follow her on Twitter @AKMcGlinchy.

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