A door-to-door COVID-19 testing survey has been halted due to multiple incidents in greater Minnesota of residents intimidating and shouting racial and ethnic slurs at state and federal public health survey teams.

The CDC pulled its federal surveyors out of Minnesota this week following reports of verbal abuse and intimidation, including an incident in the Iowa border town of Eitzen, Minn., in which a survey team walking to a house was blocked by two cars and threatened by three men, according to state health officials. One man had his hand on a holstered gun.

Frustration with the state's pandemic response "is totally understandable," said Dr. Ruth Lynfield, state epidemiologist, "but that is distinctly different than taking out frustration on another human being who is trying to help and is especially galling when there is a taint of racism. There is no justification for this — the enemy is the virus and not the public health workers who are trying to help."

Surveyors had been fanning out to 180 neighborhoods this month — offering free diagnostic testing for active COVID-19 infections and blood antibody testing to identify prior infections — to understand the true prevalence of the coronavirus causing the pandemic.

Insults came at doorways, from angry people approaching the surveyors or just people walking their dogs on the other sides of the streets, said Stephanie Yendell, a state senior epidemiology supervisor.

The surveyors trapped in the Eitzen incident were permitted to leave and did not file a police report about the gun-toting man or the two others who approached them.

Messages left with the Eitzen City Clerk were not returned Friday, but the city's mayor later that evening issued a written statement about the incident, stating that one city official and two town residents approached the surveyors peacefully and never uttered racial slurs.

Mayor Jeffrey Adamson also said in the statement that there was no gun and that the surveyors may have mistaken a large radio for a weapon.

The frequency of problems became clear last weekend when surveyors discussed their experiences, Yendell said. A Hispanic surveyor was called one slur "more in the last week than in her entire life," she said.

Most people were polite in all areas of the state, but there were "several" incidents and "a pattern emerged," said Dan Huff, assistant state health commissioner. The state ended the survey rather than continuing without the CDC workers, or sending only white surveyors in largely white rural communities.

"We found that our white teams had a very different experience, a much more positive experience, but I think from our perspective it's ridiculous for us to contemplate that," he said. "We choose who is doing this survey on their professional qualifications."

While samples were collected from 400 volunteers, that is short of what was sought for assessing COVID-19's presence in Minnesota. In a sad irony, health officials said that people who drove surveyors away due to frustration over state pandemic restrictions ended up short-circuiting a study that could have hastened the end to those restrictions.

"We had hoped through the CASPER survey to have a better understanding of how COVID-19 was spreading in Minnesota and how it was affecting people," Lynfield said. "That kind of understanding could have helped us improve multiple aspects of our response."

CASPER stands for Community Assessment for Public Health Emergency Response, a door-to-door survey that collects demographically representative responses in communities to determine needs following disasters such as oil spills and hurricanes.

Since Minnesota's first positive infection in March, the state has reported nearly 2,000 COVID-19 deaths and more than 94,000 infections. Federal health officials have estimated that every one known case could represent 10 unknown people who had mild or no symptoms but carried and spread the virus.

The monthlong survey was the largest attempt in Minnesota to assess that level of mystery spread, mostly through seroprevalence testing of blood to see if people had antibodies indicating an immune system response to the coronavirus that causes COVID-19.

The forced end to the study is an amalgam of 2020's overriding tensions — the anger over prolonged business restrictions to limit COVID-19 and the racial tensions following police killings of Black people that resulted in protests and riots, and some predominantly white counterprotests.

State health leaders said it was disappointing for Minnesota and that CASPER surveys have been completed this year in Georgia and Hawaii and are ongoing in other states. The Hawaii study assessed joblessness amid the pandemic.

In Minnesota, survey teams included at least one person asking questions and a nurse obtaining lab samples from volunteers. In addition to 12 CDC workers, the state had six workers going door to door along with 22 hired nurses and three local public health workers.

State health officials had expected some resistance but in the form of people declining testing.

Incidents occurred mostly in central and southern Minnesota, rural areas where there has been pent-up resentment over the spring statewide shutdown, the indoor mask mandate and the bar and restaurant restrictions. Such measures were seen as overkill in small towns where virus transmission has been less prevalent.

A CDC spokesperson declined to comment.

Compared to others, this CASPER survey had heightened potential for controversy, because opponents of Minnesota's COVID-19 response have questioned whether broad testing is inflating infection numbers and exaggerating the scope of the pandemic.

Some people with respiratory symptoms have refused testing for fear that a positive result would force them and their families into quarantine, or push local schools to cancel in-person classes and events.

"When staff reported this incident to us, we took it very seriously and have no reason to doubt the details," Scott Smith, an MDH spokesman, said Saturday morning. "This and other reports were serious enough that CDC decided to recall their teams and the study was ended."

Jeremy Olson • 612-673-7744