The United States passed another terrible pandemic milestone on Friday, surpassing 700,000 deaths from Covid-19 just as the spike from the delta strain begins to slow and provide some respite to overburdened hospitals.

It took 3.5 months for the number of deaths in the United States to rise from 600,000 to 700,000, owing to the variant's rapid dissemination among uninfected Americans. The death toll exceeds the population of Boston.

This milestone is especially upsetting for public health experts and front-line medical professionals because immunizations have been available to all eligible Americans for nearly six months. The doses have been shown to reduce hospitalizations and deaths significantly. An estimated 70 million eligible Americans are still unvaccinated, fueling the variant.

“You lose patients from Covid and it should not happen,” said Debi Delapaz, a nurse manager at UF Health Jacksonville who recalled how the hospital was at one point losing eight patients a day to Covid-19 during the summer surge. “This is something that should not happen.”

The number of people in hospitals across the country with Covid-19 has dropped to roughly 75,000, down from over 93,000 in early September. New cases are on the decline, with an average of 112,000 a day, a drop of about one-third over the last two and a half weeks.

Deaths appear to be decreasing as well, averaging around 1,900 per day compared to more than 2,000 about a week ago.

The summer outbreak has subsided as a result of more individuals using masks and being vaccinated. The drop in case numbers could also be attributed to the virus having consumed all susceptible people who have a shortage of fuel in some areas.

In other news, Merck announced on Friday that its experimental pill for people suffering from Covid-19 reduced hospitalizations and deaths by half. If regulators approve it, it will be the first pill for treating Covid-19 — and a significant, easy-to-use new weapon in the pandemic's arsenal.

All coronavirus treatments now approved in the United States require an IV or injection. On Friday, Dr. Anthony Fauci, the government's top infectious disease specialist, warned that some people might interpret the positive trends as an excuse to avoid getting vaccinated.

“It's good news we're starting to see the curves” coming down, '' he said. “That is not an excuse to ignore the need to be vaccinated." Unknowns include how the flu season will strain already overburdened hospital staff and whether those who have refused to be vaccinated will reconsider.

“If you're not vaccinated or have protection from natural infection, this virus will find you,” warned Mike Osterholm, director of the University of Minnesota's Center for Infectious Disease Research and Policy. ‍

Our Lady of the Lake Regional Medical Center in Baton Rouge, Louisiana, began seeing an increase in Covid-19 hospitalizations in mid-July, and by the first week of August, the facility was completely full. It halted elective surgeries and brought in military doctors and nurses to assist with patient care.

With all cases closed, the military team is set to depart at the end of October.

Dr. Catherine O'Neal, the hospital's chief medical officer, said the rate of hospitalizations isn't decreasing as quickly as cases in the community because the delta variant is affecting more young people who are otherwise healthy and are staying in the intensive care unit on ventilators for much longer.

“It creates a lot of ICU patients that don't move anywhere,” she said. And many of the patients aren't going home at all. In the last few weeks, the hospital saw several days with more than five Covid-19 deaths daily, including one day when there were 10 deaths.

‍“We lost another dad in his 40s just a few days ago,” O'Neal said. “It's continuing to happen. And that's what the tragedy of Covid is.” As for where the outbreak goes from here, “I have to tell you, my crystal ball has broken multiple times in the last two years,” she said. But she added that the hospital has to be prepared for another surge at the end of November, as the flu season also ramps up.

‍Dr. Sandra Kemmerly, system medical director for hospital quality at Ochsner Health in Louisiana, said this fourth surge of the pandemic has been harder. “It's just frustrating for people to die of vaccine-preventable illnesses,” she said.

On August 9, Ochsner hospitals had 1,074 Covid-19 patients at the peak of this most recent wave. As of Thursday, the figure had dropped to 208.

Other hospitals are also experiencing decreases. At its peak in mid-August, the University of Mississippi Medical Center had 146 Covid-19 patients in its care. On Friday, that figure had dropped to 39. Lexington Medical Center in West Columbia, South Carolina, had over 190 patients in early September, but only 49 on Friday.

But Kemmerly doesn't expect the decrease to last. “I fully expect to see more hospitalizations due to Covid,” she said.

Like many other health professionals, Natalie Dean, a professor of biostatistics at Emory University, is taking a cautious view about the winter. It is unclear if the coronavirus will take on the seasonal pattern of the flu, with predictable peaks in the winter as people gather indoors for the holidays. Simply because of the nation's size and diversity, there will be places that have outbreaks and surges, she said.

Furthermore, the uncertainties of human behaviour complicate matters. When faced with a risk, people take precautions that slow viral transmission. Then, feeling safer, people mix more freely, causing a new wave of contagion to spread.‍

"Infectious disease models are different from weather models," Dean said. "A hurricane doesn't change its course because of what the model said." One influential model from the University of Washington projects new cases that will bump up again this fall. Still, vaccine protection and infection-induced immunity will prevent the virus from taking as many lives as it did last winter.‍

Nonetheless, the model predicts that approximately 90,000 more Americans will die by January 1, for a total death toll of 788,000 by that date. According to the model, nearly half of those deaths could be avoided if almost everyone wore masks in public.‍

“Mask wearing is already going in the wrong direction,” said Ali Mokdad, a health metrics sciences professor at the university. “We must ensure that we are prepared for winter because our hospitals are overburdened.”