Two hundred million is an enormous number.

       But as the world recorded the 200 millionth detected case of coronavirus infection, that daunting figure — more than the populations of Germany, France and Spain combined — also fails to capture how far the virus has embedded itself within humanity.

       While always an imperfect measure of a virus that causes no symptoms in many of the people it infects, with many infections going unreported, case counts have provided a useful tool for much of the pandemic — like a flashing red light in the cockpit of a jetliner warning of imminent danger.

       A surge in case numbers has too often been followed by a crush of people crowding emergency rooms. And then, several weeks later, fatality counts have typically spiked. It took more than a year for the pandemic to reach its 100 millionth case, and little more than six months to double that, with the world surpassing the 200 million figure on Wednesday, according to the Center for Systems Science and Engineering at Johns Hopkins University.

       The number of those killed by the virus is also staggering.

       The official tallies stand at more than 614,000 deaths in the United States, 558,000 in Brazil and 425,00 in India. Mexico has recorded more than 240,000 fatalities, and Peru nearly 200,000. Britain, Colombia, France, Italy and Russia have each recorded well over 100,000 deaths. The global toll as of Wednesday was about 4.25 million — a serious underestimate, experts say, given the discrepancies in the way nations record Covid deaths.

       As the coronavirus continues to find new hosts across the planet at a rapid rate, the emergence of the Delta variant — thought to be about twice as infectious as the original version first detected in Wuhan, China — is adding fuel to a fire that has never stopped raging.

       In one week alone, from July 19 to 25, nearly four million cases were recorded by the World Health Organization — a jump of 8 percent from the previous week.

       With many of the new infections occurring in countries lacking vaccines or among the unvaccinated, 69,000 Covid deaths were recorded that week.

       Despite lockdowns, travel restrictions, mask mandates, business closures, social distancing and radical shifts in individual behaviors, the virus continues to find a way to spread.

       Some countries, like Australia, had success keeping case counts low thanks to geographic isolation and strict lockdown measures. But that may not be possible given the rise of the Delta variant. And governments are facing increasingly angry protests while trying to enforce lockdowns on weary populations and struggling businesses.

       Over the last six months, however, the calculus for measuring the danger of the moment has become more complicated. A rise in case counts alone, in many places, may not presage a flood of very sick people.

       For countries where vaccines are scarce, the math of the pandemic remains unchanged. Indonesian authorities reported nearly 57,000 new cases on one day in mid-July, seven times as many as a month earlier, the highest figure since the pandemic began. Twelve days later, more than 2,000 died in a single day, and the country now is nearing 100,000 dead from Covid-19.

       The Coronavirus Outbreak ？

       Latest Updates Updated Aug. 4, 2021, 9:35 p.m. ET

       ‘You’ve lost your minds.’ N.J. governor rebukes anti-vaccine demonstrators. Milwaukee Bucks’ championship games may be linked to a steep rise in cases, officials say. Biden administration has plans to require most foreign visitors to be vaccinated.

       But in nations fortunate and rich enough to have ample vaccine supplies, public health officials are watching anxiously to see how thoroughly mass inoculation campaigns have severed the link between case counts and pressure on health care systems.

       In Britain, where nearly all legal curbs on social interactions were ended on July 19, there are hopeful signs that with nearly 75 percent of people over the age of 18 fully vaccinated, the virus has run out of fuel for the moment. After a steep rise in June and early July, the number of new infections has been dropping for two weeks.

       Yet in Israel, one of the first countries to vaccinate the vast majority of the most vulnerable residents, the number of breakthrough infections among the vaccinated has led the government to offer booster shots to everyone older than 60. Germany now also plans to offer booster shots to older residents, people deemed clinically vulnerable and those who received vaccines considered somewhat less effective.

       Understand the State of Vaccine Mandates in the U.S.

       College and universities. More than 400 colleges and universities are requiring students to be vaccinated for Covid-19. Almost all are in states that voted for President Biden. Hospitals and medical centers. Many hospitals and major health systems are requiring employees to get the Covid-19 vaccine, citing rising caseloads fueled by the Delta variant and stubbornly low vaccination rates in their communities, even within their work force. In N.Y.C., workers in city-run hospitals and health clinics will be required to get vaccinated or else get tested on a weekly basis. Federal employees. President Biden announced that all civilian federal employees must be vaccinated against the coronavirus or be forced to submit to regular testing, social distancing, mask requirements and restrictions on most travel. State workers in New York will face similar restrictions. Can your employer require a vaccine? Companies can require workers entering the workplace to be vaccinated against the coronavirus, according to recent U.S. government guidance.

       The W.H.O. on Wednesday called for a moratorium on booster shots until the end of September in an effort to help all countries inoculate 10 percent of their populations.

       In the United States, with more than 90 million people eligible for shots who have not had them, experts warn that a rise in cases this winter is inevitable.

       “I don’t think we’re going to see lockdowns,” Dr. Anthony S. Fauci, the director of the National Institute of Allergy and Infectious Diseases, said on Sunday. “I think we have enough of the percentage of people in the country — not enough to crush the outbreak — but I believe enough to not allow us to get into the situation we were in last winter. But things are going to get worse.”

       The spread of the virus among the vaccinated is being intensively watched around the world, and much remains unknown. Are there differences in breakthrough infections depending on which vaccine is administered? How long does it take for protection to fade? And, perhaps most importantly, how will a rise in breakthrough infections affect hospitalization rates?

       Public health officials are confident that there is little evidence to suggest that the virus has found a way to escape the main goal of vaccines: preventing serious sickness and death.

       But the virus is now an inescapable part of our world of 7.8 billion people.

       “We have to understand that this virus is now endemic,” said Robert West, a professor emeritus of health psychology at University College London who is a subcommittee member of SAGE, a scientific body advising Britain’s government on policy. “And that we have to be thinking about our long-term strategies for dealing with it as a global phenomenon.”

       “It is now inevitable that we’re going to be looking at thousands, if not tens of thousands, of deaths a year from this virus for the foreseeable future,” Mr. West said, “in the same way that we see deaths from other causes.”