Public health experts are warning Americans of a possible second wave of new coronavirus infections in the fall and winter, but they're saying the coming surge could look different than wave of infections that occurred when the epidemic first hit.

How 9 countries responded to Covid-19—and what we can learn to prepare for the second wave

Public health experts warn of a second wave of Covid-19

As students return to school and temperatures drop, Americans will spend less time outside—where the risk of transmitting the new coronavirus is lower—and more time inside, where the risk of transmitting the pathogen is higher. As a result, public health experts expect the United States could see another wave of new coronavirus cases during the fall and winter.

John Brownstein, a Harvard Medical School professor and ABC News contributor, explained, "As the fall approaches, you have drier conditions. More people are spending more time indoors, so generally the virus is more efficient."

Brownstein also said infections may spike in the fall is because students who return to in-person classes will not be "practicing the same level of social distancing and mask wearing" as they did during initial waves of the epidemic.

In addition, public health experts for months have been sounding alarms of a "nightmare" that could occur if the United States sees its traditional flu season mixed with high rates of coronavirus transmission.

But because we know more about addressing the disease, we may fare better, experts say

However, despite the likelihood of another surge in infections, public health experts are saying a second wave of new coronavirus cases likely will look different than previous surges.

According to public health experts, one reason a second wave of infections may look different than previous spikes is because providers now have a better understanding of how to treat Covid-19, the disease caused by the coronavirus. As a result, while the United States may experience an influx of new coronavirus cases, it could see fewer deaths stemming from those infections.

"In terms of absolute numbers, we are learning much more about how to treat patients with serious complications compared to at the start of the pandemic," Brownstein said. "Now that we know more effective protocols and treatments, the number of deaths will likely go down."

For example, Lester Johnson, vice chancellor of clinical affairs at Ochsner LSU Health Monroe, said, "There's been some tremendous changes and improvements with the use of convalescent serum … plus the use of … steroids such as dexamethasone in proper dosages and of course the antivirals." (In fact, the World Health Organization recently updated guidance recommending the use of low-cost steroids to treat hospitalized patients with severe cases of Covid-19, based on an analysis showing the drugs reduced the risk of death among such patients by one-third.)

Separately, Amanda Logue, CMO at Lafayette General Hospital, said providers also have found alternative methods to help patients with Covid-19 who are experiencing labored breathing. At the beginning of the epidemic, many providers would place patients on ventilators, which resulted in high death rates, research showed. Now, providers are using less-invasive techniques to provide patients with oxygen, including interventions such as nasal oxygen and proning, which helps ease labored breathing.

In addition, Johnson said providers have learned more about how Covid-19 affects the entire body and therefore are able to take some preventive action to mitigate those outcomes. He explained, "Over the last four months, we have seen the systemic process of this disease, and we've understood that multiple systems are involved rather than, as we thought earlier, that it was a Covid pneumonia primarily."

For instance, Logue said she treats nearly all of her Covid-19 patients with blood thinners, which serve as a preventive treatment for the vascular issues and inflammation patients can experience. "The inflammatory side of this virus is causing people to have vascular side effects in the realm of strokes, blood clots, and things like that, that end up bringing them back to the hospital," Logue said. "So we're pretty aggressive with that approach now, as long as a patient can tolerate it. And we feel that it's working."

The second wave may also hit younger patients who are more likely to recover, experts say

Experts also believe the expected second wave of new coronavirus cases will look different than initial surges because they expect infections to occur primarily among younger patients, rather than older ones.

For example, in Louisiana—which experienced an initial wave of infections that hit in March, peaked in April, and then declined for a couple of months before seeing a second, ongoing wave of infections that began in July—people under the age of 30 account for 37% of infections currently, up from 17% of cases during the initial surges.

Logue said the trend is mirrored in her own experience. Lafayette General Hospital is "admitting a lot more 40-year-olds than we had the first time around, even 30- and 20-year-olds," she said, adding, "Our average age in non-ICU hospital beds is around 55, and that is about a decade younger than the first time around. 

Similarly, Wildes said, "Early on, we really focused on the elderly 65+ years of age with underlying conditions. As we reopen, we see a lot of young people getting the virus. Most young people do not have underlying conditions, so they do a lot better than the older, more susceptible populations."

Public health experts noted that older populations appear to be more likely to adhere to social distancing and other strategies that mitigate the risk of coronavirus transmission. And these expectations seem to be playing in areas currently experiencing their second waves, experts say.

For instance, in Louisiana, while the state's ongoing second wave of infections has resulted in 75% more cases of the novel coronavirus than during its initial surges, the second wave has accounted for just one-third the number of deaths when compared with initial surges. And at Lafayette General Hospital, specifically, the current death rate for patients hospitalized with Covid-19 is 14%, down from 19% during initial surges earlier this year, Logue said.

Similarly, a resurgence in the number of coronavirus infections in Europe in the past few weeks has not yet overwhelmed hospitals—or resulted in as many deaths—as did Europe's initial wave, the Washington Post reports. For example, while Spain is reporting almost as many new coronavirus cases per day as it did in March, the new cases this time around seem to be occurring primarily among younger patients, and the rate of hospitalizations has remained manageable for the country's hospital system.

Ultimately, however, it will be critical that people maintain the prevention habits they've adopted since the epidemic first hit to mitigate the potential for a second wave of new cases this fall, experts said. "When it comes to infections, there are prevention techniques we know work, including physical distancing, social distancing, mask wearing, and mindful hygiene/hand washing," said Jay Bhatt, an ABC News contributor and former CMO of the American Hospital Association (Von Oehsen, ABC News, 9/7; Stobbe, AP/ABC News, 7/21; Capps, Lafayette Daily Advertiser, 8/16; Birnbaum, Washington Post, 8/28).