This article has been updated.

We don’t know when President Trump contracted the coronavirus or from whom. We know that he might have contracted it at any point two weeks to two days before his first positive test or his first sign of symptoms, which occurred Thursday and (apparently) Wednesday, respectively. So that gives us a range of anywhere from first infection on Sept. 16 to first infection on Tuesday.

Generally, though, it takes five to seven days for an infection to be detected, which might include several days during which the individual is contagious but not showing symptoms. Given the regularity at which Trump is tested, though, it’s less likely that he was contagious without detection for an extended period of time. But the rapid tests on which the White House relies are imperfect, adding more uncertainty to the question.

What we do know is that, over the past week, the president had close contact with people on numerous occasions, during which he might have exposed others to the virus.

The risk of spreading the virus depends very much on where people interacted, how many were present and, of course, whether they wore masks. A study from a British research team published in August in the BMJ (originally the British Medical Journal) included a matrix showing how air circulation and even the behavior of those present in a group setting affected the likelihood of spread. It looked something like this.

Given the extent to which venue, prevention efforts and crowd size matter, we looked at Trump’s schedule over the past week to evaluate the extent to which he participated in events that the British team would identify as high-risk for transmission.

Friday, Sept. 25

Trump began the day at his private club in Miami. In the morning, he held a roundtable event at the club focused on the Latino vote. More than 100 people were in the audience, according to a report from the White House press pool. Trump sat onstage at the front of the “dimly lit, fiercely air-conditioned” room, per the pooler.

“His seat is at the center of a long table, with four people seated to each sides,” the pool report read. “Ahead of his arrival, all eight were wearing masks but a few minutes before the president entered a man in a suit came up and spoke to them, upon which they removed their masks.”

The group spoke for just shy of an hour.

Indoors, speaking, probably well ventilated, no masks, lengthy duration. Not crowded onstage, so medium risk.

Trump then traveled on Air Force One to Atlanta for another event.

For all Air Force One travel: Indoors, probably speaking, probably well ventilated, no masks, lengthy duration. Probably crowded, so high risk.

On the tarmac, he spoke briefly with a small group of elected officials.

For all tarmac meetings: Outdoors, speaking, no masks, short duration, small group. Low risk.

In Atlanta, Trump gave a speech about employment in the Black community. It’s unknown what interactions he had with other speakers backstage. The White House generally screens attendees for the virus before they interact with Trump — but, of course, that doesn’t prevent Trump from spreading the virus to them.

Indoors, speaking, probably well ventilated, no masks, lengthy duration, distanced from the crowd. Medium risk.

That risk assessment applies to the risk from Trump to the attendees. Among the attendees, the risk was greater, given the pool reporter’s description of the audience: “Approximately 200 people in the audience, nearly all of them African Americans. Zero social distancing. A great many not wearing masks.”

After the Atlanta event, Trump traveled back to D.C. for a roundtable event at his private hotel in the city. It’s not clear how many people attended.

Indoors, speaking, probably well ventilated, probably no masks, lengthy duration, probably an intimate group. High risk.

That evening, Trump had a rally at an airport in Newport News, Va.

Outdoors, speaking at a distance from others, no masks, lengthy duration. Medium risk.

Saturday, Sept. 26

Trump began his day with an Oval Office event described as “a greeting with Evangelical Faith Leaders.” It’s not clear whether his was in person or over the phone.

This event is a good reminder, though, that Trump is constantly surrounded by other people in the White House.

For most White House activity: Indoors, probably speaking in close quarters, probably no masks, lengthy duration. High risk.

The marquee event of the day was his nomination of Amy Coney Barrett to serve on the Supreme Court. Trump hosted Barrett and her family for the announcement, outlining her qualifications in a brief speech.

Outdoors, generally speaking at a distance from others, no masks, lengthy duration. Medium risk.

The person who spent the most time in proximity to Trump during the event was Barrett, who stood to his side. She has reportedly tested negative for the virus. Sen. Mike Lee (R-Utah), who attended the event, announced Friday morning that he has tested positive for the virus. Later in the day, Sen. Thom Tillis (R-N.C.) did as well. A number of other senators — including Josh Hawley (R-Mo.), Deb Fischer (R-Neb.) and Ben Sasse (R-Neb.) — also attended, as did Attorney General William P. Barr. A number of Trump allies, including Fox News’s Laura Ingraham, former White House staffer Kellyanne Conway and Trump’s former campaign manager Corey Lewandowski were also there. On Friday, Conway also reported testing positive.

Two others who were at the White House that day have since tested positive. The president of the University of Notre Dame, where Barrett is on the faculty, announced Friday that he had. A member of the press corps did as well.

If any of those infections occurred at the White House on Saturday, it may have been during receptions related to the nomination which were held inside the building. There, The Post reports, people interacted in close quarters and largely without masks.

Indoors, close distance, talking, no masks. High risk.

Another rally was held Saturday night, this time at an airport in Harrisburg, Pa. The risk of infection from Trump was equivalent the risk at his rally in Virginia, though, again, that doesn’t hold for the rally’s attendees.

“Masks usage is mixed. Hard to say. Could be 10% of the crowd. Could be 25%,” the pool report stated. “Lots of folks near the press have masks lowered, around their neck.”

Outdoors, speaking at a distance from others, no masks, lengthy duration. Medium risk.

Sunday, Sept. 27

In the morning, Trump headed to his private golf club in Sterling, Va., for a round.

On the course: Outdoors, probably speaking at a distance from others, no masks, lengthy duration. Medium risk. In the clubhouse: Indoors, probably good ventilation, probably no masks, unclear duration. Medium risk.

That afternoon, Trump held a news briefing that lasted a bit under an hour.

Indoors, probably good ventilation, no masks, speaking at a distance from reporters for a lengthy duration. Medium risk.

Also on hand at the news briefing were former New York mayor Rudolph W. Giuliani and former New Jersey governor Chris Christie. Neither was masked; each was aiding Trump in preparations for the upcoming presidential debate. Christie has told ABC News that he is awaiting test results.

In the evening, Trump hosted a reception for the families of service members killed in combat. The event was held at the White House, with attendees sitting close together without masks. Trump offered brief remarks, according to a video released by the administration.

Indoors, probably good ventilation, no masks, speaking at a distance for unknown duration. Unclear whether there was person-to-person interaction, although it seems likely. Medium risk.

Monday, Sept. 28

Trump’s first event was an outdoor presentation of a new electric truck from Ohio’s Lordstown Motors. Also in attendance were several employees of the company, White House trade adviser Peter Navarro and Sen. Rob Portman (R-Ohio).

Outdoors, no masks, speaking at a distance for a relatively brief duration. Low risk.

Later in the day, the White House held an event in the Rose Garden to tout a (previously announced) expansion of coronavirus testing. A number of administration officials attended, including Education Secretary Betsy DeVos and Health and Human Services Secretary Alex Azar.

Vice President Pence, who was also there, warned that the expansion — combined with an existing surge in cases in a number of states — would mean an increase in the number of cases over the short term.

Trump said at another point.: “As we do more tests, you’re going to have automatically more cases. We are relentlessly focused on protecting the vulnerable while enabling healthy Americans to go back to work.”

“I say it, and I’ll say it all the time: We’re rounding the corner,” he said as he concluded his remarks.

Outdoors, no masks, speaking at a distance for a relatively brief duration. Low risk.

That evening, Trump did debate prep with staffers and allies, including Christie, Giuliani and Conway. The group also included Trump counselor Hope Hicks, who tested positive for the virus Thursday.

Indoors, probably no masks, probably no distancing, probably speaking at length. High risk.

Tuesday, Sept. 29

Trump, his family and many of his top aides traveled to Cleveland in the early afternoon to attend the debate that evening. After a walk-through of the venue around 4:30 p.m., the retinue went to a nearby hotel to await the beginning of the debate.

Indoors, probably good ventilation, probably no masks, probably little distancing, probably speaking at length. High risk.

The debate began a bit after 9 p.m. on the grounds of the Cleveland Clinic, a top-tier medical facility. There was a small audience, with attendees sitting at some distance from one another, but mask use was spotty.

Trump spoke — and, at times, shouted — for 90 minutes as he and former vice president Joe Biden interacted. The pair were at some distance from each other and moderator Chris Wallace.

“I don’t wear a mask like him,” Trump said at one point. “Every time you see him, he’s got a mask. He could be speaking 200 feet away from him and he shows up with the biggest mask I’ve ever seen.”

Biden has since tested negative, though if he does have the virus it may not yet be detectable.

Indoors, probably good ventilation, no masks, speaking and shouting at length while distanced. High risk.

Trump and his group then flew back to Washington.

Wednesday, Sept. 30

Trump’s day began with a meeting with Treasury Secretary Steven Mnuchin at the White House. Mnuchin has tested negative for the virus — though, again, it can take a number of days for an infection to be detectable.

Indoors, probably good ventilation, probably no masks, speaking at length, probably in proximity. High risk.

In the afternoon, Trump traveled to Minnesota for a fundraiser and rally. On arrival, he was greeted by a number of officials.

The fundraising event was held at a supporter’s house in Shorewood, Minn. Trump spent about an hour there. It’s not clear how many others attended. A political reporter from Minnesota who had seen photos from the event told a local radio station that, after Trump left, “staff and guests lingered” and that they “sang karaoke, they had their arms around each other.”

Indoors, probably good ventilation, probably no masks, speaking at length, probably in proximity. High risk.

After the fundraiser, Trump held a rally at an airport in Duluth, Minn. He spoke for about 45 minutes — shorter than his normal rally speeches.

“Many wearing face masks, most not,” the pool report read. “It is very chilly, with a cold breeze.”

Outdoors, speaking at a distance from others, no masks, lengthy duration. Medium risk.

After the rally, the president returned to Washington.

Thursday, Oct. 1

On Thursday morning, Hicks tested positive for the virus. Trump nonetheless continued with his planned schedule.

In the early afternoon, he traveled to his private club in Bedminster, N.J., for a fundraising roundtable. (White House Chief of Staff Mark Meadows said Friday that they learned of Hicks’s diagnosis as they were leaving for the Bedminster event.) As is generally the case when Trump travels to that club, details of his visit were withheld from the media. It’s not clear how many people participated in the event, but New Jersey’s governor is encouraging them to quarantine.

Outdoors, probably good ventilation, probably no masks, speaking at length, probably in proximity. Medium risk.

Earlier in the day, Trump recorded a speech for the Alfred E. Smith Memorial Foundation Dinner, held every year to benefit Catholic charities.

“I just want to say that the end of the pandemic is in sight,” he said in those remarks.

Natalia Jimenez contributed to this report.