That depends on the specific infection. For instance, Sickle Cell Anemia distorts the normal circular shape of the red blood cells. In general, however, every infection causes an increase in white blood cells whose job it is to fight off infections/intruders in the body. Infections lead to full-blown disease which often attacks, mutates, or destroys healthy red blood cells as a way to continue living inside the host. If you have a specific infection or disease in mind, search for results of that particular culprit on the blood cells of the host. Good luck, and thanks for using enotes!