Is it a mitzvah or aveirah for a man to come to shul to daven with a minyan when he is coughing the entire time and spreading bird flu/black plague/etc.?

Now I'm going to worry for a few days that I'll become ill.

people with colds/flu should form their own minyanim?
i would imagine in winter there are quite a few such people davening in any given shul... part of the winter deal.

(maybe try to take vitamins to boost your immune system?)

Obviously aveirah. People are always ready to miss shul for a million other reasons (such as a shiur or a bris ) and this man should learn that the tzibur comes before his own personal selfish desire to daven with minyan.

i rem. there was incident in my yeshiva where one of the rebbes said a guy couldnt come to the bais and be really yeshivish and learn even though he was sick cuz he didnt want the yeshiva to get sick
I dont think its an aveira - just not to cool