If there's a knock at the door and folks asking to test you for COVID-19 or ask a few questions about the pandemic, don't shut and lock the door on them.

Teams from the Minnesota Department of Health are conducting a voluntary survey, going door to door in the Rochester area to randomly selected homes asking residents to take part in the Centers for Disease Control and Prevention's Community Assessment for Public Health Emergency Response (CASPER) survey.

The survey is designed to gather information that will help public health experts determine how COVID-19 has spread in Minnesota communities, understand what caused COVID-19 to spread in certain areas, explore how COVID-19 transmission and infection rates differ in various regions of Minnesota, identify the percentage of people who are infected but asymptomatic, and improve health messaging and help stop the spread of COVID-19, according to the MDH.

In addition to the surveys, the MDH teams will offer on-the-spot nasal and blood tests to check for COVID-19 infection or antibodies, MDH noted.

Kari Etrheim, public information officer for Olmsted County Public Health, said the teams will be in Rochester through Wednesday — operating from 10 a.m. to 7 p.m. — and can be identified by team members wearing bright orange vests that say "COVID-19 Survey Team." The team members will also have MDH identification badges.

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"They'll be wearing masks," Etrheim said, "and if people agree to do a survey or (get tested), they'll put on more personal protection equipment."

The Olmsted County Sheriff's Office sent a note via its Facebook page letting residents know not to be alarmed if a team shows up at your door. Simply ask for identification and, if you choose to take part in the survey and/or testing, then do so.

Etrheim said OCPH had a few phone calls from people wondering if the offer for testing at their front door is real.

"We've had a couple asking 'Is this legitimate?' and rightfully so," Etrheim said.

The MDH notes that no one is required to participate in the survey, but free COVID-19 tests are a big benefit for participants.