Two presumptive positive cases of coronavirus infections at two public schools have led to temporary closures in Oregon and Washington state, health and school officials said, as districts nationwide navigate uncharted waters of risk regarding children and virus containment after the first death in the U.S. is reported.

A student at Jackson High School north of Seattle is presumed to have the virus, state health officials said Friday, the same day a presumptive case of infection of a Forest Hills Elementary employee outside Portland was announced by the Oregon Health Authority.

The temporary shutdowns of both schools come amid a national flurry of preparations and advance work districts have undertaken to mitigate exposure and anticipate outbreaks, the Associated Press reported, including online lesson planning, reviews of attendance requirements and scrubbing down schools to kill any virus remnants.

The unnamed patients on the West Coast, who have been quarantined at hospitals, have not traveled outside the United States or had known contact with infected people. Health officials have said they do not know how they acquired the deadly virus locally — indicating a higher risk of spread.

“The tried and true public health method is to contain the virus, go to who they have been in contact with and isolate people who could be exposed,” said Albert Ko, a professor of epidemiology and medicine at the Yale School of Public Health.

But now that the virus may have circulated inside the schools for some time, and tracing its origins at this point is a baffling task, containment can be a particular challenge, he said. “We really don’t know where we stand or how widespread it is,” Ko told The Washington Post on Saturday.

The Jackson High school student in Mill Creek, Wash., became ill on Monday with fever and body aches, the Seattle Times reported. He felt better and returned Friday, but left after his tests returned positive.

In neighboring King County, health officials confirmed the first coronavirus death in the United States.

The school employee in Oregon did not come into regular contact with students, Lake Oswego Superintendent Lorna de la Cruz said, though it is unclear what position the person holds.

Both schools were shut down and are expected to reopen this week after crews disinfect the buildings. Experts aren’t certain how long the coronavirus can live outside the body, Ko said, though its cousins — SARS and MERs — can survive on surfaces up to nine days.

Coronavirus is transmitted through respiratory droplets, not in aerosol form, so a focus on wiping down bathrooms, door handles and other places commonly touched with alcohol-based solutions will go far, he said.

Children are transmission engines for respiratory viruses such as influenza, given their close contact with one another, and they don’t have a long history of exposure to disease, said Caitlin Rivers, an epidemiologist at the Johns Hopkins Center for Health Security.

But she stressed initial studies of the coronavirus show older people and adults in poor health are the most at risk. “There’s not a lot of evidence children are particularly prone to infection,” Rivers told The Post on Saturday. “We just don’t know.”

The virus has infected 83,000 people globally and caused more than 2,800 deaths, most of them in China, where much of the understanding on the impact it has on children was learned, Ko said.

“A big question is can children be infected but not show symptoms and transmit it to other people,” Ko said. “I think that’s unknown.”

The Centers for Disease Control and Prevention have provided guidelines to schools both unexposed and exposed to coronavirus, including reviewing emergency preparations, monitoring absenteeism and preparing for students or staff who may contract the virus.

One particular focus, Rivers said, is what happens to students when schools begin to shutter.

“If schools are closed and you have children just recongregating in other places, that’s not going to help with the social distancing needed to control transmission,” she said.

Rivers, who has children of her own, said school closure decisions are always a balance of benefit and risk. One thing to keep in mind, she said, is that they have a disproportionate effect on low-income parents who depend on schools for child care and on children who receive free and reduced school meals.

“If closures are going to happen, communities need to be planning now how to help with those kinds of situations,” she said.

The two school transmissions come amid exposure in two other communities about 90 miles apart in California.