Um actually,colds can be really,really debilitating-and I'm also speaking from experience!And yeah,of course working through them is something you have to figure out a way to do most of the time,but sometimes they can make you feel too rotten to do that 100 %,and the reason people are concerned is that Andy plays a sport in which physical fitness is paramount,especially at his level.Even tiny things being wrong can make a great deal of difference in his sport.Someone figuring out a way to go to school,or a job that doesn't require a great deal of physical activity through a nasty cold which has them wheezing is very different than Andy having to charge around a tennis court with it.
I didn't,unfortunately,see the match or the media stuff afterwards,so I can't give my personal opinion on his appearance health-wise,but from many comments-and not just this site-it does appear he was,very noticeably,coughing and wheezing a lot.So while we shouldn't jump to conclusions and start panicking that illness is going to mess everything up for him,I certainly don't think it's unreasonable to express a bit of concern about him.
Of course it can be debilitating.
From what I saw, Andy looked like he had the tail end of a cold, and something that wouldn't be particularly debilitating in day to day life. If it was me, I'd be able to get on with my work with next to no problems. I can manage my work load, so I'd avoid doing anything too physically tiring, and make sure I have a cup of tea to hand so that I can take a drink if I start coughing during a telephone call etc. With a heavier cold, I would probably still pitch up to work, but if at all possible, I'd avoid doing anything that requires too much brain power that could go wrong if I make mistakes, and I'd definitely be wearing a hole in the carpet between my desk and the kitchen making hot drinks.
The last few months everyone has been talking about whether or not Lendl has given Andy an extra few percent, and that it's just a few percent difference between a slam winner and runner up. A bit of a cold makes a difference by just a few percent too. Against a much lower ranked player, it's fine. Against a tougher opponent, it could make all the difference. It's one thing to power through, but another to perform your absolute best.
Obviously, he had no bother finishing off yesterday's match despite being a few percent down, and it is hard to judge just how many percent it was. Probably not many, and probably not enough to cause serious problems today either.