19-40 makes up 0.25% of the deaths (4 in total) [0]
In the US, of people aged 20-44, "only" 2.0-4.2% are admitted into ICU, significant, but making up only 12% of the ICU admissions, and 20% of the hospitalizations. [1]
I think you're confusing "dead" with "in the ICU". If you listen to the various interviews with Italian Drs, you'll learn that to make a recovery from the full-blown infection requires spending weeks on ventilation. So looking at the deaths count does not accurately capture the real problem, which is that you have an accumulated pile of people who are severely sick but will probably make some sort of recovery eventually. In the meantime your health system is offline.