"I raised my hand and said, 'Scarlet fever can make you go blind, right?'" The instructor hesitated and responded, "I don't think so."
The disease that Mary Ingalls probably had is called meningoencephalitis (muh-NING-go-en-sef-ah-LY-tis). It can be caused by bacteria and treated with antibiotics, but Tarini said it's likely she had the viral kind, which can be spread by mosquitoes and ticks.
The viral disease is fairly common today, particularly in summer months and can cause fever, headaches and sometimes seizures, said Dr. Buddy Creech, an infectious disease specialist at Vanderbilt University. Affected children typically require hospitalization but lasting effects are uncommon, Creech said.
Still, blindness can occur if the disease affects the optic nerve, and it's entirely possible that Mary Ingalls had the condition, he said.
Historian William Anderson, author of Laura Ingalls Wilder biography, said various theories about Mary Ingalls' blindness have been floating around for years. The new analysis provides credible evidence that it was caused by something other than scarlet fever, but it does nothing to discredit the books, Anderson said.
"From a literary standpoint, scarlet fever just seemed to be the most convenient way" to describe Mary's illness, he said.