The coronavirus was always expected to make a comeback this winter, but an autumn rebound in infections across Europe and North America could make the colder months even more daunting than public health officials had anticipated.
The pandemic's resurgence is less deadly so far than during its bleak early months, when thousands were dying daily. The risk is that with official case numbers already jumping to records in many countries, caring for the sick will overburden hospitals.
The return of the virus has been particularly pronounced in Europe, where long lockdowns brought the virus to heel following a deadly spring. After authorities eased restrictions in an effort to jump-start their economies, infection rates began climbing in Spain, France and other nations in August, fueled by vacationers and the virus's insidious ability to spread from asymptomatic people.
"When people went on vacation they really let their guard down," said White House Coronavirus Task Force coordinator Deborah Birx at a Friday press briefing in Cambridge, Massachusetts. "We're asking now that you're back from vacation, put your guard back up, not only in the public places but in your private places, including your home."
The impact is being felt in both Europe, where many people take holidays in August, and in the U.S., where the effect has been creeping northward in the east and Midwest, Birx said. People should stop assuming that their families and close friends are free of infection just because they appear healthy, she said.
"We take down our guard when we're with people we know, and we assume that if I know you, you couldn't have Covid," she said. "The message has to change that we're giving to the community, that community spread is now occurring in small gatherings day after day in households and families."
Infection rates are spiraling across much of the European continent. Over the past month, France has reported about 340,000 new cases, close to half the country's cumulative total since the outbreak began. Yet deaths have risen by less than 1,800 -- a rate of about 0.5% -- after the country previously recorded more than 30,000.
The U.K. has seen a similar trend. Countries that were less affected the first time around, such as the Czech Republic, became hot spots this fall. Even Germany, which weathered the spring better than many of its neighbors, is seeing growing case rates.
In the U.S., the seven-day average of new cases climbed to 46,824 Thursday, the most since Aug. 19, according to the most recent Johns Hopkins University data. One trouble spot is New York City, where outbreaks in a handful of neighborhoods and suburbs have stirred fears that the former U.S. virus epicenter could see a second act.
The virus's vigorous return is happening even as the weather across much of the Northern Hemisphere remains temperate. Experts have long warned that as more people are forced inside, and as flu season kicks into gear, Covid-19 will surge. The spurt in infections across the globe means health officials will have little time to retrench and cope with what could be a taxing winter for health-care systems around the world.
"It is a problem that we know this thing gets transmitted by going inside, with large crowds, for prolonged periods," said Ezekiel Emanuel, vice provost for global initiatives at the University of Pennsylvania. "And the winter months are all about going inside for prolonged periods of time."
Retailers, restaurants and businesses in the U.S. have worked hard to make public places safe from the virus, Birx said. The rising numbers are an indication that spread is taking place when people least expect it, which may be among their own household members, she warned.
Colleges and universities are already getting positive results with frequent testing of students and staff for the virus and an emphasis on prevention in all situations. The task force has been reminding governors that if the virus is allowed to gain momentum again, it will quickly translate into more hospital surges.
"It's inevitable we will have a rise," Emanuel said. "We do have a chance to control it and limit it. That's the hope."
There may be some comfort in that Europe's latest surge has so far been less lethal than in the past. While France and the U.K. reported 24-hour death tolls of more than 1,000 on some days last spring -- with Italy and Spain close behind -- current levels have been less than one-tenth that high on most days.
Over the past month, for example, France's death rate of 0.5% compares with double-digit percentages in that country and others at the height of the first wave.
Health officials cite several reasons for a decline in the mortality rate, including younger, healthier patients, improved treatment and a massive ramp-up in testing.
The U.K. has increased testing by more than 10-fold from levels last spring. Back then, only those with symptoms were likely to be tested; now, with increased contact tracing, the net has been cast far wider, and the majority of positive tests in Italy, the U.K. and other countries are for asymptomatic cases.
Case tallies during Europe's first wave were probably vastly understated, making the death rate from the disease seem artificially high. The World Health Organization has estimated that about one-tenth of the world's population has had Covid. That would be more than 750 million people -- 20 times the official total of about 37 million.
In that case the actual death rates would have been far lower as a percentage of positive cases. Now, with far more testing, health authorities are getting a better picture of the pandemic's true lethality -- one reason why there's been less enthusiasm for full lockdowns as the virus spreads again. Instead, European countries are tackling the contagion with a patchwork of local restrictions.
Another difference now is that some new treatment options have emerged. Gilead Sciences Inc.'s remdesivir is more widely available, and the generic steroid dexamethasone is showing promise in preventing inflammation, a problem in acute cases. President Donald Trump touted Regeneron Pharmaceuticals Inc.'s experimental antibody therapy after receiving it for Covid-19, and the company joined Eli Lilly & Co. in applying for emergency-use authorization.
Disclaimer: This article first appeared on bloomberg.com, and is published by special syndication arrangement.