...Mexico is battling one of the worst coronavirus outbreaks in the world, with more than 52,000 confirmed deaths, the third-highest toll of the pandemic. And its struggle has been made even harder by a pervasive phenomenon: a deeply rooted fear of hospitals.

The problem has long plagued nations overwhelmed by unfamiliar diseases. During the Ebola epidemic in 2014, many in Sierra Leone believed that hospitals had become hopeless death traps, leading sick people to stay home and inadvertently spread the disease to their families and neighbors.

For a spiky sphere just 120 nanometers wide, the coronavirus can be a remarkably cosmopolitan traveler.

Spewed from the nose or mouth, it can rocket across a room and splatter onto surfaces; it can waft into poorly ventilated spaces and linger in the air for hours. At its most intrepid, the virus can spread from a single individual to dozens of others, perhaps even a hundred or more at once, proliferating through packed crowds in what is called a superspreading event.

Of all the coronavirus’s qualities, perhaps the most surprising has been that seemingly healthy people can spread it to others. This trait has made the virus difficult to contain, and continues to challenge efforts to identify and isolate infected people.

Since April, the Trump administration has funneled $48 million into a program with the Mayo Clinic, allowing more than 53,000 Covid-19 patients to get plasma infusions. Doctors and hospitals desperate to save the sickest patients have been eager to try a therapy that is safe and might work. Tens of thousands more people are now enrolled to get the treatment that’s been trumpeted by everyone from the president to the actor Dwayne Johnson, better known as The Rock.

It begins with a mild fever and malaise, followed by a painful cough and shortness of breath. The infection prospers in crowds, spreading to people in close reach. Containing an outbreak requires contact tracing, as well as isolation and treatment of the sick for weeks or months.

This insidious disease has touched every part of the globe. It is tuberculosis, the biggest infectious-disease killer worldwide, claiming 1.5 million lives each year.

ROME — When the coronavirus erupted in the West, Italy was the nightmarish epicenter, a place to avoid at all costs and a shorthand in the United States and much of Europe for uncontrolled contagion.