The US's third coronavirus surge may become the deadliest yet, experts say

• Daily coronavirus cases in the US have risen nearly 40%, on average, since the start of October.
• Experts worry these cases will lead to the nation's deadliest surge of infections yet, as more people gather indoors for the holidays and become more lax about masks and social distancing.
• The US is also approaching peak flu season, which can lead to overcrowding at hospitals.

The 1918 flu pandemic sparked three waves of infections, the deadliest of which occurred in the fall. The US is now on track to see a similar trend, experts say. The nation's new daily cases have risen nearly 40%, on average, since October 1.

Experts predict this third surge could be the deadliest yet due to a perfect storm of factors.

Scientists expect cases to rise as people gather indoors and spend time with family during the holidays. Winter will also bring peak flu season, which can lead to crowding at hospitals. At the same time, many Americans are becoming more lax about social distancing and mask wearing as pandemic fatigue sets in. And the US still isn't much better at contact tracing than it was at the start of the pandemic. So once a cluster of cases ignites, it's left to spread like wildfire.

That leaves the country in a precarious — and unprecedented — position going into the fall.

"My worry is that we're just going to be completely overwhelmed," Megan Ranney, an emergency-medicine physician at Brown University, told Business Insider. "Even if we do better on a case-by-case basis, I think that the number of deaths that we're going to experience this fall and winter is going to dwarf what we've already been through."

It might be a different story if the US had managed to lower its baseline of cases to less than 10,000 per day, experts say, since that would make subsequent spikes less dramatic. But the lowest cases ever got after the spring surge was around 20,000 per day.

The nation is now seeing nearly 60,000 daily cases, on average.

The University of Washington's Institute for Health Metrics and Evaluation predicts that nearly 170,000 more people in the US could die from now through February 1.

The third surge is more rural and widespread

During the second surge over the summer, the US got better at diagnosing milder cases as testing became more widely available. Younger people also made up a much larger share of cases compared to the spring. Combined, these factors made the second peak less deadly than the first.

But experts worry about the prospect of increased cases among older residents this fall.

"With the advent of the holidays, and the increased indoor time, it means that we are going to be getting potentially older people sicker — people that had managed to avoid infection up until now," Ranney said.

The latest surge is also more widespread than its predecessors. All but five states have seen cases rise in the last two weeks, with Midwestern states particularly hard-hit.

"Our entire healthcare system is going to be stretched at the same time," Ranney said. "The second thing that concerns me is that it is more rural, so it's occurring in hospitals that have less capacity to begin with."

Indeed, the states with the highest current numbers of new cases per capita — North Dakota, South Dakota, and Montana — have particularly large rural populations: more than 40% of the states' totals.

Flu season creates an unprecedented challenge

Widespread adoption of masks and social distancing could reduce the number of flu cases this fall. This has already happened in Australia, which recorded just 21,000 flu cases as of August 23, compared to more than 247,000 by that same time the year before.

But Americans are becoming less compliant with public-health restrictions as the pandemic wears on, creating more opportunities for the flu and coronavirus to spread simultaneously.

Since COVID-19 shares many of same symptoms as seasonal influenza, Ranney said, doctors will be inclined to treat any report of flu-like symptoms with extreme caution.

"It's going to be really tough for us as physicians to tell one from the other in the early stages," she said. "God forbid that people get co-infected with both. We don't even know what that's going to look like."

Treatments may prevent some deaths, but not all

Physicians have gotten better at treating COVID-19 since the start of the pandemic. In critical cases, doctors usually prescribe the steroid dexamethasone. A major UK clinical trial found that the therapy significantly reduced the chance that a critically ill patient would die.

There are also two FDA-approved treatment options for hospitalized patients: remdesivir and convalescent plasma. Together, these advances may have had some effect on lowering COVID-19 death rates in the US.

"We know more about how to treat people with severe COVID now than we did six months ago," Ingrid Katz, an assistant professor at Harvard Medical School, told Business Insider." Trump was one of the lucky beneficiaries of that, and there are others who are like him who may survive now, who would not have survived back in March."

A soon-to-be-published study in the Journal of Hospital Medicine found that mortality among hospitalized patients in one New York City health system dropped by 18 percentage points from March to August. At the start of the pandemic, patients in the study had a 26% chance of dying, the researchers found. But by the end of the study, patients only had an 8% chance of dying.

Still, scientists remain skeptical of the benefits of the treatments the FDA has authorized so far. Some say it's too early to know whether convalescent plasma is really a useful therapy, while others have questioned whether remdesivir reduces mortality.

"On the chance that it may help people, we're using it, because there aren't better options right now," Ranney said.

Meanwhile, doctors are still struggling to keep patients alive, and many hospitals continue to run low on tests and personal protective equipment, along with certain drugs.

"We have no magic bullets," Ranney said. "Despite Trump's claims, there are no cures right now. In fact, I'm hearing reports from colleagues in some locations across the country that are running out of remdesivir and convalescent plasma. We have dexamethasone abundantly right now, but we've experienced shortages of that in the past."

Ranney said doctors should brace for a 30% increase in hospitalizations next week and a 30% increase in deaths two or three weeks from now.

"The only thing right now that we can do to change that is to change our behavior and reduce the number of infections," she added. "But remember what we're going to see in terms of infections two weeks from now reflects our behavior today. So we're already two weeks behind the ball."