Dr. Bruce Dart, the director of the Tulsa Health Department, said Tulsa County had reported nearly 500 new cases of Covid-19 in the past two days.

Supporters looked on as President Trump spoke at a rally in Tulsa, Okla., on June 20.
Credit…Doug Mills/The New York Times

A surge in coronavirus cases in and around Tulsa, Okla., is probably connected to the campaign rally President Trump held there last month, the city’s top health official said on Wednesday.

Tulsa County reported 206 new confirmed cases on Tuesday and 261 — a record high — on Monday, and Dr. Bruce Dart, the director of the Tulsa Health Department, said at a news conference that it was reasonable to link the spike to the rally and related events.

“The past two days we’ve had almost 500 cases, and we know we had several large events a little over two weeks ago, which is about right,” Dr. Dart said. “So I guess we just connect the dots.”

The county has more infections right now than any other in Oklahoma, and “we’ve had some significant events in the past few weeks that more than likely contributed to that,” he added.

Asked whether contact tracing had confirmed a link between the rally and the increase in cases, Leanne Stephens, a spokeswoman for the health department, said it “will not publicly identify any individual or facility at risk of exposure, or where transmission occurred.”

Ms. Stephens said this week that contact tracers had been “completely inundated” trying to track down dozens of close contacts for thousands of confirmed cases, a task that can take hours for each person.

Karen Keith, a county commissioner in Tulsa who oversees the area where the rally occurred, said in an interview on Wednesday that contact tracers were struggling to persuade people to reveal where they had been, frustrating local officials.

The county’s seven-day rolling average of new cases dipped briefly at the end of June before rising again, and has been increasing fairly steadily since July 2. Mr. Trump held his rally on June 20, and because of the incubation period between when people are infected and when they start showing symptoms, it can take around two weeks for a change in infection rates to become apparent.

Oklahoma Coronavirus Map and Case Count

A detailed county map shows the extent of the coronavirus outbreak, with tables of the number of cases by county.

Health officials were worried from the start about Mr. Trump’s decision to hold a large rally indoors — a much riskier environment than outdoors in terms of coronavirus transmission — in a state where coronavirus cases were already spiking.

A few days before the event, Dr. Dart urged the president to cancel, calling the rally a “perfect storm of potential over-the-top disease transmission.”

When he said that, Tulsa County had just recorded 89 new cases in a day, a record high at the time. This week, the daily totals have been more than twice that.

New York Times