Coronavirus rise in northern states including Minnesota may signal fifth wave

At the foot of the Rocky Mountains, Tom Gonzales, director of public health in Colorado's sixth-largest county, made a decision in mid-October that felt like a dismaying retreat in the battle against the coronavirus. He reinstated an indoor mask mandate.

It was not a popular move, but Gonzales felt he had no choice. In Larimer County, which stretches eastward from the Continental Divide to the high plains and encompasses the city of Fort Collins, hospitals were overwhelmed by a surge of COVID-19 patients that began slowly in August, plateaued for a while - and then exploded unexpectedly once the leaves began to turn.

By the end of last week, the number of COVID-19 patients in the county's hospitals matched the peak in December 2020.

"Everyone was like, 'No, not again, please,'" Gonzales said. "There've been lots of twists and turns in this pandemic where we're really surprised - and this is the biggest surprise for me."

Colorado's setback is not an outlier on the national landscape. The late summer and early autumn easing of the nation's burden of new coronavirus infections has come to a halt over the past two weeks, according to health department data analyzed by The Washington Post. Dramatic drops in caseloads in the Deep South, including the high-population states of Florida and Texas, have been offset by increases in the Mountain West and the northern tier of the country.

Twenty-four states have seen at least a 5% increase in cases over the past two weeks, led by New Hampshire with a 63% increase, Vermont with 50%, New Mexico with 48%, Minnesota with 42% and Nebraska with 37%. The aggregate national caseload, having eased for two months, begin ticking up after hitting a low of about 69,000 new cases a day in late October. On Tuesday that average topped 75,000.

The looming question is whether this is the start of what would be the fifth national wave of infections since the start of the pandemic - and if so, what the amplitude of that wave might be.

But the disease burden has never been evenly distributed across the country. The places hardest hit recently tend to have low vaccination rates, and include much of rural America.

A year ago, news that two vaccines were remarkably effective against the coronavirus seemed like a light at the end of the tunnel. But the picture that has emerged since is more complex.

A sizable chunk of the population is ardently opposed to getting vaccinated. And the vaccines, though extremely effective, cannot provide a perfect shield against infection. Antibodies wane naturally over time, a fact driving the government's push for boosters among the most vulnerable populations - and the potential expansion of eligibility to every adult. The highly transmissible delta variant has shown its power, fueling rapid surges that burn out quickly, but also outbreaks that grow more gradually, like the pattern seen in Colorado.

"I think we're all disappointed that we're here today," Scott Bookman, COVID-19 incident commander for the Colorado Department of Public Health and Environment, said at a news conference last Friday. "When the first vaccines arrived in the state in the middle of December of last year, I really did think we were moving beyond this part of the pandemic."

The good news is that hospitalizations and deaths still appear to be declining nationally. Progress in vaccinations and improved clinical care have made the virus less lethal. Still, the virus is taking more than 1,200 lives every day on average.

"I think we've all learned to respect this virus and how rapidly circumstances can change," said James Musser, chair of the Department of Pathology and Genomic Medicine at Houston Methodist Hospital. The flu has barely registered there so far this fall, and the number of patients hospitalized with COVID-19 has dropped from 800 in September to 125 now, he said.

With Thanksgiving, Christmas and other holidays looming, respiratory viruses will have abundant opportunities to make a cold-weather run through the population. The social landscape is changing as people renew their pre-pandemic habits - including indoor dining, travel, family gatherings, parties and concerts.

"These vaccines defanged the virus for the majority of individuals. That is a wonderful thing," said Monica Gandhi, an infectious-disease doctor at the University of California at San Francisco. "The endgame of coronavirus is to make it into a circulating respiratory virus that does not cause severe disease, and then we live with it."

Another factor confounding predictions is that immunity wanes over time, necessitating boosters. The virus has demonstrated that it is quite capable of breakthrough (post-vaccination) infections, and although such cases typically aren't severe, they contribute to the spread of the disease.

Europe, where vaccines have been widely embraced, has seen a massive wave of new infections, and it has often been about a month ahead of the United States during the pandemic.

Michigan is now experiencing its fourth wave of rising hospitalizations since the start of the pandemic. On Tuesday, Beaumont Health, which operates eight hospitals in metropolitan Detroit, counted 373 hospitalized patients with COVID-19, about two-thirds of them unvaccinated.

Although those numbers haven't yet approached the levels of previous waves - the last one, fueled by the alpha variant, peaked at 800 patients this spring - the steady increase since August suggests this could be a protracted surge, said Nick Gilpin, Beaumont's medical director for infection prevention.

"This has been a two-and-a-half to three-month slow burn," Gilpin said, noting that previous spikes tended to play out relatively quickly. "This is different. This is way more of a marathon than a sprint. It feels like we're going to be continuing this slow burn through the winter months, and that's going to be exhausting for a lot of our people."

The reasons for the uptick include colder weather, increased indoor gathering and relaxation of precautions in the wake of news reports showing declining national infection rates. Vaccination rates in Michigan are relatively low. And immunity is waning among vaccinated people who rushed to get their shots early in the year, Gilpin said. Anecdotally, most of the breakthrough cases resulting in hospitalization are among those with chronic health problems and compromised immune systems, he said.

In Larimer County, Colo., meanwhile, the arrival of fall and cooler weather coincided with a surge in viral infections that strained the health care system. There are not enough beds for the sickest COVID-19 patients, with ICU beds full, said Gonzales, the public health director. By last Friday, the number of coronavirus patients in the hospitals had tied the all-time high in December - when vaccines were not yet available - although the number decreased early this week.

The state's chief medical officer this week also urged anyone over 18 to get a booster shot if it has been six months since their second Pfizer or Moderna shot, or two months since their Johnson & Johnson vaccine.

"I would never have guessed that," Gonzales said of the hospitalization spike. "... This has been quite a surprise and a twist in the whole pandemic that has been quite a challenge for our community and hospitals."

Cases in Colorado began rising in August, but more slowly than in other regions of the country. Hospitalizations stayed relatively high in September, without fluctuating much up or down. After a month, they started to swing upward again. A report released last week estimated that 1 in every 48 people in the state are infectious.

"After that plateau, most of the states had started coming down and we had some simulations suggesting it would start coming down in Colorado," said Jude Bayham, an economist at Colorado State University who works with the team modeling the state's outbreak. "We saw the opposite."

Many of the same factors playing out in Michigan are thought to be driving the uptick in Colorado - cooler weather pushing people indoors, easing up on masks with no statewide mandate and large pockets of unvaccinated people, even in a state where 72% of people over age 12 have gotten the shots.

Colorado's trajectory may not augur the winter everywhere in the country, but it does highlight that regional outbreaks, driven by a sometimes mysterious mixture of forces, will likely continue to occur as long as pockets of people remain unprotected.

Vaccinations remain the most powerful weapon, and reaching people who haven't been vaccinated is crucial. But immunity can wane in a gradual way that varies from one person to the next, influenced by multiple factors, including how they responded to the vaccine and even which shot they received.