As mentioned in many other posts Leo has a high chance of winning almost any 1v1.
Here's what I think. Since SEN games get the most views riot intentionally gave Leo covid-19.
Also I swear not too long ago sacy was wearing a face mask? What if they gave it to sacy to give it to Leo.
Also team heretics was sick as well so maybe Leo passed it down to them afterwards but they had the vaccines so they recovered quick.