We disinfect the mats before every class, but no matter how careful you are, if you are in close proximity to others you should take steps to minimize your chances of getting sick from anything on the mats (inlcuding staph, flu and other bad things). Here are some simple things you can do to protect yourself:
1) wear a long sleeve rashguard and your gi pants. In the summer people tend to want to roll no-gi, but rolling in shorts and a t-shirt puts more of your skin in direct contact with the mat.
2) if you are sick, stay home. No one wants your flu! you might feel well enough to go to work, but don't roll with people unless you are completely well. Some people in class have babies at home, so be considerate. If you are sick, feel free to watch class and take notes if you want, or ask someone to go over what you missed when you get back.
3) take a shower as soon as you get home. Simple soap and water will kill the staph virus, and it takes a couple of hours for it to take hold, so you have plenty of time to wash your hands/take a shower.
4) care for the mats. we disinfect the mats before each class, but if you walk off the mats barefoot and then walk back on, you will track germs on it. Have some flip flop sandals that you can put on when you leave the mat so your bare feet don't touch the floor in other parts of the gym.
5) bandage up your cuts. staph infections usually happen when you have a cut and it comes in contact with something that is not sterile. keep your cuts bandaged when you are rolling. If you don't have bandages or tape, ask someone in class for it (usually several people have some).