Fever
When the borreliosis bacterium enters the body, the body reacts by causing a temporary increase in temperature. They work faster to try and fight off the infection. The body increases the production of lymphocytes (white blood cells) to fight the infection. The excess amounts of white blood cells affect the hypothalamus, which makes the body heat up, causing a fever. Usually, a rise in body temperature causes you to feel cold, and you may start to shiver.
Chills
Fevers are often accompanied by chills. This is when you start to feel cold, though not necessarily in a cold environment, often accompanied by shivering or shaking. Chills occur when the muscles expand and contract repeatedly, and the vessels in the skin constrict. It is often due to an underlying illness, including Lyme disease.