If a person is sick or in pain, it is normal for blood pressure to be higher than usual, according to Group Health. Blood pressure normally rises and falls throughout the day based on a person's activities.
Certain viral infections, such as cytomegalovirus, can cause high blood pressure, according to a study by Beth Israel Deaconess Medical Center. When a person is battling a virus and fever is present, blood pressure can rise as the body works to fight off the infection. Additionally, fever can speed up heart rate and body temperature. As heart rate increases, blood pressure increases, especially when dehydration is present.