MILWAUKEE - In the race against COVID-19, a new opponent is gaining steam in Wisconsin.
More people are being vaccinated, but Wisconsin health officials say the state is also seeing a steepening increase in cases.
Health officials said it is only a matter of a few weeks before the B.1.1.7 variant -- also known as the U.K. variant -- becomes the dominant strain in Wisconsin. The CDC director said Wednesday that B.1.1.7 is already the dominant strain nationally.
"The CDC has identified five variants of concern," said Dr. Ryan Westergaard, chief medical officer with the Wisconsin DHS Bureau of Communicable Diseases. "All five of these strains are currently in Wisconsin."
Officials said more contagious and more dangerous strains of the coronavirus are contributing a 100% increase in the state's seven-day average number of cases over the past month.
Westergaard said cases are increasing most rapidly among children.
"We are in a new phase of the epidemic that is clearly worse than it was before and it's transmission among young people who are driving the change and the curve," Westergaard said.
Despite the uptick, hospitalizations have remained low. It is an indicator, Westergaard said, that the vaccine is working.
While people ages 65 and older are most at risk of serious illness from the virus, more than 75% of seniors have received at least their first shot.
"We should feel good, the degree to which we've protected our older Wisconsin residents," said Westergaard.
Julie Willems Van Dijk, the DHS deputy secretary, reminded residents Thursday that the only way to win the race is with both the vaccine and continued vigilance.
"There may not be a statewide mask mandate anymore, but that doesn't decrease one iota the need for everybody to behave like there is statewide mask mandate," said Willems Van Dijk.
Experts are still looking at the data to determine why transmission of variants is so high among children. They say a number of factors could play a role, including schools reopening and spring sports resuming.
Children under the age of 16, meanwhile, are not yet eligible for the vaccine.