Rock County’s epidemic curve shows fewer people have reported the onset of COVID-19 symptoms in recent days compared to this time last month.

And while that and smaller day-to-day increases of positive coronavirus cases are encouraging, it by no means indicates the pandemic is over, said Nick Zupan, epidemiologist at the Rock County Public Health Department.

The state Department of Health Services is now publishing county epidemic curves for COVID-19 on its website.

Epidemic curves track when people with positive cases of the novel coronavirus began showing symptoms.

Data for May 20 to June 3 could change as more people are diagnosed and tested.

The coronavirus is thought to remain active in a person’s body for about two weeks, so people who test positive in coming days might have shown symptoms days prior.

Those who do not show symptoms are placed on the chart by date of diagnosis.

Typically, epidemic curves are used to help identify a disease during an unknown outbreak and monitor how it spreads through a community, Zupan said.

For example, if there is an outbreak of a food-borne illness, health officials can look at an epidemic curve to help determine which disease is circulating based on how long it took for symptoms to appear after exposure.

COVID-19 is different because officials know what disease they are tracking.

Epidemic curves for COVID-19 show periods of time when more people started showing symptoms, which could help connect the dots on what led to an increase in cases or local outbreak.

Peaks and valleys in reported onset dates indicate Rock County’s large increases in coronavirus cases are mostly tied to localized outbreaks at facilities, such as the outbreak at the Birds Eye food processing plant in Darien, Zupan said.

The day with the most reported cases of symptom onset was May 19, with 39 cases.

Rock County saw symptom onset peaks in late April and mid-May.

Zupan said he expects the county to continue seeing peaks and valleys of coronavirus cases until there is a vaccine.

Rock County has 658 confirmed cases of coronavirus, and 19 people have died, according to health department data.

Of those with positive cases, 15% have been hospitalized.

In Rock County, 207 people have recovered from the virus.

Safety precautions such as wearing masks in public, staying home and social distancing have helped prevent exponential growth of cases in Rock County, Zupan said.

Easing precautions could lead to an increase in cases as long as the virus remains in the community, Zupan said.

The county has not seen a large spike in cases since reopening businesses, Zupan said, but residents should remain cautious and follow recommended guidelines.