Pure speculation, and possible confirmation bias, but your immune system weakens when you're exhausted.
3 in a year isn't crazy, but it seems like more than normal. Just a guess, but 1-2 seems average, with many having none. You'd think Cale should have a strong immune system, being such a high level athlete, that probably has a very good diet, so he'd be closer to the lower side of average, rather than the higher.
Often when high level athletes get sick, it's because they pushed their bodies physically past the limit they should, and their immune system crashes.
He played a ton of minutes recently too and those are hard minutes Cale plays.
Feb 2 - 26:51
Feb 4 - 30:36
Feb 6 - 26:43
Feb 7 - 29:11
Feb 12 - 28:06 (Four Nations)