These are new cases reported. In health and crime, it's usually not possible to know if an increase in reported cases is caused by more instances happening, or by an improvement in detection and / or issue awareness.
These are US cases. It's impossible to infer anything about world tendencies.
It's explicitly said the group at greatest risk are LGBT males. Not pedos, and not minors having sex with pedos.
It does say it's the largest number ever. It does not say anywhere that the increase is 20%. It can be a minuscule increase which still gives the largest number ever.
Recommendations are monogamy and condom use. Not legal bans on sexual activity.