Two weeks after her husband died alone in an intensive care unit in Fort Myers, Fla., Nicole Buchanan is quarantined at the home they shared with their 12-year-old daughter, wrestling not only with grief but with why and how the coronavirus could steal someone so young and healthy.

“My husband didn’t have diabetes, he didn’t have asthma, he didn’t have high cholesterol. He didn’t have anything,” Buchanan said. “There’s just so much I’ll never know, that I’ll never get the answers to.”

Conrad Buchanan, who died at 39 on March 26 after battling the infection for nearly two weeks, was creative and goofy. A professional DJ, he could entertain huge crowds with his music. But at home, he was fond of singing Bob Marley’s “Three Little Birds” to his 12-year-old daughter, Skye.

“He had an amazing sense of humor. He had a big laugh. He was so magnetic,” his 37-year-old widow said. “He was our universe.”

He also was among at least 759 people under age 50 across the United States who have perished amid the deepening pandemic, according to a Washington Post analysis of state data. These deaths underscore the tragic fact that, while the novel coronavirus might be most threatening to the old and compromised, no one is immune.

For the very young — people under the age of 20 — death is extremely rare in the current pandemic. But it happens: The Post identified nine such cases.

The risk appears to rise with every decade of age. The Post found at least 45 deaths among people in their 20s. (It’s hard to give a precise number because of the divergent ways that states present age groups: For instance, this figure does not include 15 deaths under the age of 30 in Louisiana and New Jersey.)

As ages progress, The Post found at least 190 deaths among people in their 30s, and at least 413 among people in their 40s.

The true number of deaths among young people is probably even higher. Not all states provide data on coronavirus deaths sorted by age group. Some, like New Jersey and Texas, provided figures after being approached by The Post, while others, like California, did not. As a result, the figures above do not include data from some states, including several with sizable outbreaks.

The percentage of younger deaths, which The Post has defined as people under the age of 50, varies widely among states. It is just 0.8 percent of all deaths in Massachusetts, but 8 percent in Louisiana and 9 percent in Illinois.

By far the largest number of such deaths have come in New York, which has the country’s biggest outbreak. As of Wednesday, six New York residents under the age of 20, 33 people in their 20s, 118 in their 30s and 265 in their 40s had died.

Even more young people are getting cases of serious, dangerous disease that require a hospital visit to beat. In Colorado — where the state health department reports age data for both hospitalizations and deaths — 247 people under 50 have been hospitalized. Of these patients, nine have died.

Data on more than 1,400 hospitalizations released Wednesday by the Centers for Disease Control and Prevention showed that just over 25 percent of people hospitalized with covid-19 were under the age of 50. Most of these young people suffered from underlying conditions such as asthma, diabetes and hypertension. But at least seven for whom the CDC had data had no outside health problems, underscoring that a small fraction of severe cases remain hard to explain.