We had a lot of barncats at the farm where I grew up. They were helpful in killing rats and mice. When the cat population became too large, a disease would hit the group and many of them died within a month.
When people crowd into huge cities, it can’t be healthy. A virus will run its course and move on. Some victims will not recover, but some will and will have immunity, providing the researchers with clues to develop a vaccine.
Clearly squeeze is needed.