PONTIAC, Mich. (AP) — Gov. Gretchen Whitmer said Friday that a factor in Michigan’s surging COVID-19 cases is fewer people were infected earlier in the pandemic than in other states, and she expressed concern about spring break travel to Florida.

Florida and Michigan have reported the highest and second-highest number of cases of a more contagious variant that was first identified in the U.K. Michigan had the United States’ worst infection rate in the past two weeks.

“Yes, I am concerned” about travel between the states, the governor told reporters while attending the opening of a large-scale vaccination site in Oakland County. “It’s a concern no matter what. That’s why we are really encouraging people to get vaccinated.”

She urged people returning from Florida to work from home and have their kids learn virtually for at least a week. She and health officials later recommended that people get tested after in-state, out-of-state or international travel. Michigan will provide about three-dozen pop-up testing sites to make it easier for travelers.

The variant first identified in the U.K. is up to 50% more transmissible than the virus that surged last spring and again in the fall, making it more adept at thwarting measures that were previously effective, according to the World Health Organization. Scientists have concluded it is also more deadly.

Whitmer remained averse to tightening restrictions that were loosened in recent months and continued to emphasize vaccines, which have been given to at least 35% of Michigan residents ages 16 and older, including more than 67% of people 65 and up. She said she will get her first shot Tuesday, alongside one of her daughters, a day after eligibility opens to everyone 16 and older.

“It’s a bit disappointing that as our vaccination rates are going up that our infection rates have not done a similar decline,” Oakland County Executive Dave Coulter said.

The state health department reported nearly 5,500 new coronavirus cases and 20 additional deaths. The seven-day average, 5,128, has grown six-fold over nearly six weeks. About 2,600 adults were hospitalized with confirmed infections, more than double the roughly 1,200 in the hospital two weeks ago.

“By the recent numbers, we know we’ve got a bit of a reality check happening,” Whitmer said. “We know that COVID is still very present and it is still a very real threat. We may be seeing light at the end of the tunnel, but we are still in the tunnel.”

She said Michigan did well keeping COVID-19 metrics low. She suggested that is a reason — along with variants, pandemic fatigue and increased travel — why there is a third wave.

“Because of that, we’ve got fewer people per capita who have antibodies than a lot of other states do,” she said. She noted that while her administration has eased restrictions, it has not gone as far as states that eliminated mask requirements.

More than 17,000 deaths in Michigan have been linked to COVID-19. More than 569,000 people had recovered as of March 26.