While recent news of the omicron variant has captured the world's attention, the delta variant continues to fuel new surges in cases and hospitalizations in many states across the United States—but delays in testing and data reporting over the holidays may mask the true severity of this latest surge.

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Covid-19 cases driven by the delta variant surge across the country

New Covid-19 cases and hospitalizations in the United States have been on the rise over the past few weeks, the Washington Post reports, leading some experts to suggest a winter surge may be on its way. On Nov. 22, the country reported a seven-day daily average of just under 93,000 cases—an 18% increase from the week before—while hospitalizations increased 6%, to around 5,600 patients per day.

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"Part of [the rise in cases] is just how our behavior changes as things get colder and we are in more places inside and in close proximity to people where infection spreads," said Amber D'Souza, a professor of epidemiology at the Johns Hopkins Bloomberg School of Public Health. "The underlying issue is the same nationwide: The pandemic is not over."

Currently, several states are dealing with new surges in Covid-19 cases and hospitalizations, with at least two dozen states seeing a 5% rise in cases over a two-week period, leading to crowded hospitals and overtaxed health care workers.

For example, Michigan saw an 86% increase in new Covid-19 cases and a 37% increase in hospitalizations between Nov. 8 and Nov. 22, the Washington Post reports. On Monday, according to Modern Healthcare, the state had 4,229 children and adults hospitalized with Covid-19.

Similarly, Minnesota has also seen a significant rise in Covid-19 cases and hospitalizations, the Post reports. As of Nov. 22, the state had the third-highest number of total new cases per capita and 1,518 Covid-19 hospitalizations—the highest number since December 2020.

Across the state, many hospitals are running out of beds as they struggle to care for patients both with and without Covid-19. "I've been in practice 20 years, and I've never seen anything like this. It's worse than the last surge," said Paul Palecek, ED medical director at the Grand Itasca Clinic and Hospital. "Our boarding times are longer. We're just routinely facing situations where there is not a bed in the state to put a patient [in]."

Colorado and various other western states are also experiencing similar difficulties finding hospital beds for patients, particularly in the ICU, amid rising case and hospitalization numbers.

"We've been at full capacity and couldn’t get patients transferred [until a few days ago]", said Jennifer Riley, VP for operations at the Memorial Hospital at Craig. "It's hard to believe we are so far into the pandemic."

Holiday testing, reporting delays could falsely sway perceived surge severity

According to the New York Times, there will likely be a decline in new reported Covid-19 cases during the holidays—but this is largely a reflection of delays in testing and data reporting from state and local health officials instead of real decreases in new infections.

Stephen Kissler, a postdoctoral fellow in immunology and infectious diseases at the Harvard T.H. Chan School of Public Health, said that similar fluctuations in reported and actual infections also appear in flu data.

According to Kissler, a surge of precautionary testing before the holidays can mean that people are less likely to get tested over the holidays even if they have symptoms. This leads to a supposed decline in cases before they increase again as people resume testing.

For example, New Jersey last year saw a large increase in Covid-19 cases after the holidays following a lag in data reporting, as well as holiday-related transmission of the virus. According to Edward Lifshitz, medical director of the Communicable Disease Service at the New Jersey Department of Health, the state expects to see a similar pattern this year.

In general, while cases may seemingly drop during the holidays, the actual number of new cases is likely higher and will increase in the weeks afterward as testing and reporting catch up. "It will probably take a good week or two before things settle back down and we can see what actually happened over Thanksgiving," Kissler said.

Writing on Twitter about the potential post-Thanksgiving surge, Ashish Jha, dean of the Brown University School of Public Health, said, "[Don't be surprised if cases jump above 100k/day and deaths >1k/day. It'll remind us: Whatever happens with omicron, the variant killing Americans right now is delta." (Shammas/Firozi, Washington Post, 11/25; Walsh, Modern Healthcare, 11/29; Daley, CPR News, 11/29; Richert, MPR News, 11/19; Levin/Del Giudice, Bloomberg, 11/11; Sun/Jones, New York Times, 11/22)