For months, the call for coronavirus testing has been led by one resounding refrain: To keep outbreaks under control, doctors and researchers need to deploy the most accurate tests available — ones reliable enough to root out as many infections as possible, even in the absence of symptoms.

That’s long been the dogma of infectious disease diagnostics, experts say, since it helps ensure that cases won’t be missed. During this pandemic, that has meant relying heavily on PCR testing, an extremely accurate but time- and labor-intensive method that requires samples to be processed at laboratories.

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.

In April, with hospitals overwhelmed and much of the United States in lockdown, the Department of Health and Human Services produced a presentation for the White House arguing that rapid development of a coronavirus vaccine was the best hope to control the pandemic.

“DEADLINE: Enable broad access to the public by October 2020,” the first slide read, with the date in bold.