DENVER (AP) — Colorado Gov. Jared Polis joined the nation’s top infectious disease expert Tuesday and urged people to wear masks and socially distance to help prevent stay-at-home orders and overwhelmed hospitals as cases of the coronavirus surge during the holidays.

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases and a member of the White House’s coronavirus task force, warned during a virtual news conference that Colorado is not alone in seeing a spike in cases and pleaded with people not to travel or gather in large groups.

“If you look across the United States, we are really in a public health crisis right now because we are having a surge the likes of which is worse than the surges that we all saw in the late winter, early spring,” Fauci said.

He added that “we are likely going to see a surge upon a surge” of cases, based on the number of people who traveled and gathered for Thanksgiving and on those who are expected to shop and attend holiday parties before celebrating Christmas and New Year's in large groups.

Colorado has been hit with a substantial spike in COVID-19 cases, with one in 41 residents believed to be contagious. Nearly 233,000 people in the state have tested positive, and more than 2,600 have died from the virus since it started its rapid spread in the spring, according to state health officials.

Four prison inmates hospitalized after showing symptoms of COVID-19 died this week, the Colorado Department of Corrections announced Tuesday, bringing the total number of prisoner deaths to 11 since the beginning of the pandemic. The department said 1,558 of its 14,083 inmates currently had COVID-19, about 11% of the population, while about 3% of its staff has the disease.

Vaccines are “literally on the threshold” for vulnerable populations, and the general population could start getting inoculated as early as April, Fauci said.

“Once we get there, we can crush this outbreak just the way we did with smallpox, with polio and with measles," he said. "So we can do it. We just need to hang together a bit longer.”

Officials with the U.S. Centers for Disease Control and Prevention were meeting Tuesday with the institute's Advisory Committee on Immunization Practices to determine what groups will get the vaccine first.

“They’re literally discussing it now, right now,” Fauci said.

Polis, who announced Saturday night that he and his partner, Marlon Reis, had contracted the coronavirus, encouraged residents with symptoms to get tested and echoed Fauci in pointing out that hope is on the horizon.

“We’re tired of not seeing our friends and loved ones. We’re tired of not having the quality of life we know we want to have. But you know what? We’re almost there,” Polis said.

The governor started quarantining Wednesday after he said he was exposed to the virus. He tested negative right after learning of his exposure, but his results came back positive after he was later retested.

“I’m certainly not out of the woods, nor is Marlon. As we know, this can certainly take a different turn after several days, but so far I feel very good,” said the governor, who described his symptoms as “very mild."

For most people, the coronavirus causes mild or moderate symptoms, such as fever and cough that clear up in two to three weeks. For some — especially older adults and people with existing health problems — it can cause more severe illness, including pneumonia, and death.