A research team at Columbia University and in Norway conducted a cross-control epidemiological study to determine links between known teratogenic infections and autism. The team used data from the Norway Autism Birth Cohort, which was composed of 442 mothers of autistic children and 46 mothers of non-autistic children from 1999 to 2008, matched for sex and month and year of birth. Blood samples were taken from the women taken at midpregnancy and at the time of birth to check for CMV, Toxoplasma gondii, rubella, HSV-1, and HSV-2.
The researchers found that HSV-2 infection at midpregnancy was associated with a 2x increase in risk for autism in male babies. No other associations were found and the study was underpowered to make associations for girls.
This study, while important, doesn’t make any definitive conclusions about risk factors for autism. Some scientists think that an inflammatory response in the fetus due to stress would cause autism. For example, a Swedish study showed that hospitalization during pregnancy was associated with a 30% increased risk of autism for the baby. Other scientists believe infectious vectors must be at play since autism requires drastic restructurings of the neocortex.
Read more here: http://www.sciencemag.org/news/2017/02/herpes-virus-may-be-trigger-autism