As many as 20 Minnesotans could have been in contact with the state’s second coronavirus patient before the person knew they were infected with COVID-19.

Minnesota Department of Health officials are working to identify everyone a Carver County resident was in contact with before testing positive Sunday for the coronavirus. Officials say any of those contacts who are at serious risk of developing the virus will be asked to isolate themselves for two weeks, the incubation period of the virus.

“We worked last night, late into the night, to contact some of those individuals and continued working on that this morning,” said Kathy Como-Sabetti, state senior epidemiologist.

People who were in close contact with an infected patient — within six feet for 10 minutes or more — are considered to be at high risk of contracting the virus. People with limited exposure, such as walking past an infected person, are considered to be at lower risk of getting the coronavirus.

The Carver County coronavirus patient is in their 50s and recently returned from a vacation in Europe. They began developing symptoms March 2 and sought medical treatment March 7 with a positive COVID-19 test coming back Sunday.

Both of Minnesota’s coronavirus cases are considered presumptive until the Centers for Disease Control and Prevention confirms the tests. That should happen later this week.

Wisconsin public health officials reported the state’s second case Monday, just across the Mississippi River from Minnesota, in Pierce County. The person was exposed while traveling in the U.S. and is isolated at home recovering.

Not everyone can get a coronavirus test, but Minnesota’s criteria are flexible, and Como-Sabetti said it is typically left at the discretion of medical providers. At highest risk are people with symptoms who were around someone who was infected or traveled to somewhere infections are widespread.

People hospitalized with serious respiratory symptoms may also be candidates for COVID-19 screening.

Minnesota has tested about 80 people so far and can currently test about 100 people per day. The state’s testing capabilities could soon grow as hospitals and other health care providers develop COVID-19 tests.

For now, people with suspected cases are first asked to call their medical providers for over-the-phone screening. If someone fits the testing criteria they will be asked to provide a sample for testing.

Other states have developed ways to test patients in isolation to limit exposure to others. Fairview hospital officials said Monday they were working on testing sites that would limit exposure.

Laura Reed, Fairview’s chief operating officer, said the goal “is to screen people using technology as much as possible” before referring possible patients to an online physician. If the physician says a coronavirus test is warranted, the patient would be directed to one of four Fairview clinic sites, where they’ll be swabbed in the parking lot by health care workers in protective equipment.

“It should be happening yet this week,” Reed said.

State health officials say the best way to limit the spread of COVID-19 is to wash your hands thoroughly and often, cover sneezes and coughs, don’t touch your face and stay home if you are sick.

“We definitely have a culture of people trying to tough it out and get through the day. Now is not the time to do that,” Como-Sabetti said.

Once the virus starts to spread in the community — which is already happening in California, New York and Washington state — health officials will try to use “social distancing” to slow the number of cases.

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“The point of community mitigation and social distancing is to decrease the number of cases presenting to health care at one time,” Como-Sabetti said.

That way, hospitals and clinics won’t be overwhelmed with patients.

As of Monday morning, there were 111,000 COVID-19 cases worldwide and 3,800 deaths. In the U.S. 566 cases had been reported with 22 deaths.

Frederick Melo contributed to this report.