Sadly, it won't even take a deadlier strain to accomplish this. Even if every single person who gets the virus recovers, a pandemic will cause a surge in the number of people sick enough to require hospitalization. And that alone will wreak havoc on our healthcare infrastructure.
We have, essentially, zero excess capacity in our healthcare system tpday. I was involved in a full-scale emergency response exercise a few years ago and the local ambulance company did not expect to have any ambulances to spare for use in the exercise. (They did eventually manage to find exactly one, but the real response to such a disaster would have called for many more.)
When I was helping the same health department with their pandemic response plan, we polled the local nursing homes to see what they had in terms of excess beds and respirators. The answer was, "none to speak of." --And hospitals are the same way.
Severe economic pressures force these organizations to grow leaner and leaner all the time, to trim excess capacity wherever they find it. And we haven't developed any worthwhile incentives to reverse that trend.
So people don't have to die in large numbers in order to overwhelm our healthcare system; they just have to get sick enough to require care. Indeed, the sad truth is that those who die during a pandemic may use up fewer "bed days" than those who get sick, but pull through.
Most hospitals right now couldn't deal with the results of a bus crash by themselves. In order to meet the needs of an influx of patients like that, hospitals rely on their ability to transfer (or divert) patients to other nearby hospitals. During a pandemic, however, this won't be an option, because those nearby hospitals will be equally overwhelmed.
Like many others who are looking at this problem for the first time, the authors of this article are putting an undue emphasis on mortality (death) versus morbidity (sickness) when it comes to the effects on the healthcare system. In many ways, mortality is the most important thing about a pandemic. It's certainly what worries me the most on a personal level. But when it comes to the healthcare arena, it takes a back seat to morbidity.
Because the thing that's going to transform the healthcare infrastructure from a moderately well-oiled machine into just a greasy pile of slag isn't the number of people who die, but the wholly unmanageable number of people who get sick.