Picornaviruses infect more than one billion people worldwide each year. Generally individuals contract two or three enterovirus and/or rhinovirus infections each year. In some cases the viruses get into the brain, and in some children these viruses can cause long-lasting brain injuries. "We think picornavirus family members cross into the brain and cause a variety of brain injuries. For example, the polio virus can cause paralysis. It can injure the spinal cord and different parts of the brain responsible for motor function. In the murine virus we studied, it did the same thing and also injured parts of the brain responsible for memory," Dr. Howe says.
Enteroviruses and rhinoviruses are among the most common in the picornavirus family. Certain enteroviruses (gastrointestinal illnesses among others), such as enterovirus 71, are common in Asia, particularly southeast Asia where many children are infected. Once the virus infects the host due to unsanitary conditions, it can cross over into the brain and cause encephalitis, which can lead to conditions ranging from lethargy to a coma. In recent years, scores of children have died from infection.
The degree of brain damage in humans infected with a picornavirus infection is not known, but the evidence from the mouse study suggests this is an area of research that should be explored further.
"Our findings suggest that picornavirus infections throughout the lifetime of an individual may chip away at the cognitive reserve, increasing the likelihood of detectable cognitive impairment as the individual ages. We hypothesize that mild memory and cognitive impairments of unknown etiology may, in fact, be due to accumulative loss of hippocampus function caused by repeated infection with common and widespread neurovirulent picornaviruses. Further analysis of such deficits and exploration of potential therapeutic