Public health official sees signs of herd immunity
A spokesperson for the Marathon County Health Department on Friday said a significant drop in new COVID-19 cases since a major spike in November 2020 could be evidence of some kind of partial herd immunity.
Judy Burrows said county residents should stay vigilant in fighting the coronavirus by wearing a mask, practicing social distancing and getting a vaccine if they are eligible, but with the knowledge that some combination of vaccinations and people’s past infections is helping to reduce new cases of COVID-19.
Burrows said the county’s worst week for the disease was Nov. 8-14, 2020, when 1,299 cases were confirmed. That compares with last week where there were only 64 cases. In Clark County, the number of active cases peaked at 548 on Nov. 18, 2020, and has dropped to just 19 as of March 28. Marathon County’s COVID-19 website reports days this past week where confi rmed cases were in single digits. “This is the fourth week in a row where we were under 100,” said Burrows. “We seem to be levelling off at around 65 cases per week.”
The spokesperson said that while the coronavirus has subsided, COVID-19 activity level in Marathon County is still offi cially rated as “high.” Clark County is listed as having “medium” activity.
Burrows said the overall trajectory of COVID-19 in Marathon County mirrors the experience across Wisconsin.
Asked for a theory about why COVID- 19 infections have dropped so sharply, Burrows said it is likely there are enough people in the county with antibodies, the combined result of both vaccines and past illness, to slow the spread of the disease.
Burrows said Marathon County has had nearly 14,000 confirmed COVID-19 cases and suspects the number of actual cases is far higher. The county, to date, she added, has had 25 percent of residents vaccinated. In Clark County, about 12 percent are fully vaccinated.
This combination of people seems to have partially thwarted the disease, she said.
“All of these factors working together are helping to keep the numbers low,” Burrows said.
She said the county seems to be helped by a partial herd immunity. True herd immunity, she said, occurs when 80 percent of a population has antibodies to fight off a disease.
The spokesperson underscored how the medical community still is trying to understand how COVID-19 is transmitted.
She said, for example, most experts expected to see a second surge in COVID-19 cases after the Christmas holiday, but this failed to materialize in Marathon County and for most parts of Wisconsin. It’s not known why the second spike did not occur, Burrows said. Maybe it was because so many people got sick in the first spike, she said, or, maybe, people started to wear masks and practice social distancing out of an abundance of caution because of the first spike.
Burrows said that most viruses have a bell shaped infection curve and this seems to be true of COVID-19. She cautioned, however, against comparing COVID- 19 to the standard annual flu virus.
“The annual flu follows a bell shaped curve, but that is because it is seasonal,” she said. “COVID-19 is not seasonal.”
