A map published by the Rock County Public Health Department shows the highest density of COVID-19 cases are in the 53511 and 53546 ZIP codes.
The map was published Tuesday, when the county also confirmed its fourth death from COVID-19.
As of Tuesday, there have been 59 confirmed cases and four deaths in Rock County.
The number of cases has been corrected since Monday’s report of 60 cases, according to a daily update from the health department.
Health officials say there are likely 10 people infected for every confirmed case.
The ZIP code data is based on cases as of April 9, when the county reported 47 cases and two deaths. That means at least 12 cases are not accounted for on the ZIP code map.
The map will be updated weekly, Kelsey Cordova, public information officer for the health department, said in an email to The Gazette.
The ZIP codes with the highest number of cases also have larger populations and therefore are expected to have more cases, Cordova said.
The 53511 and 53546 ZIP codes have more than 10 confirmed cases each, according to the map.
Those ZIP codes cover much of the city and town of Beloit, town of Newark, town of Turtle, southeastern Janesville, Avalon and the town of La Prairie.
The 53548 ZIP code—covering the west side of Janesville, sections of town of Janesville, town of Rock and Footville—has between five and nine cases, according to the map.
The rest of the county’s ZIP codes have fewer than five confirmed cases each, according to the map.
Health department officials for weeks had refused to release geographic information about COVID-19 cases, citing privacy concerns.
“The numbers of positive cases has reached a point where risk of individual identification by release of this information is lowered,” said Health Officer Marie-Noel Sandoval in a daily update. “... Additional information may be made available as the number of cases increases and risk of individual identification is lessened.”
The health department still has not released the municipalities where people with confirmed cases live.
Representatives from Janesville and Rock County have clashed over the release of COVID-19 data for weeks.
The Janesville City Council on Monday approved a resolution urging the release of more information, including ZIP codes and other geographic information.
The Gazette was unable to reach a representative from the city for comment before press time Tuesday.
The health department advises all residents to stay home and social distance regardless of what ZIP code they live in.
A release from the state Department of Health Services on Tuesday said safer-at-home guidelines and social distancing efforts are working across the state.
“Without effective treatments or a vaccine, the only way to slow the spread of COVID-19 is through non-pharmaceutical interventions that help us maintain physical distancing,” said Ryan Westergaard, state epidemiologist. “The safer-at-home order has been our main intervention in Wisconsin, and we are beginning to see the results.”