It has long been postulated that the blindness of Mary Ingalls (the sister of the author of the Little House on the Prairie books Laura Ingalls Wilder), was due to scarlet fever. However, review of biographical records, historical documents and other items points the finger at another disease that causes swelling in the brain and upper spinal cord. The disease referred to as "brain fever" in the 1800s was most likely meningoencephalitis and more likely to be what caused Mary Ingalls to go blind. Scarlet fever was commonly misdiagnosed in the 1800s and was greatly feared. Researchers were unable to find any documentation that Mary Ingalls had the red rash which is the trademark symptom of scarlet fever. In addition, Laura Ingalls Wilder referred to her sister's illness as "some sort of spinal sickness". The records at the college for blind students that Mary attended documented that "brain fever" was responsible for her loss of vision. Meningoencephalitis comes in both bacterial and viral forms and is spread by mosquitoes and ticks. While the viral form of the disease is pretty common it rarely has lasting effects but blindness can occur if the disease attacks the optic nerve.