New clues hint that young boys who get serious viral infections might be more likely to develop autism

Scientists may be a step closer to understanding what causes autism and how to treat it. A study released this month offers evidence that severe infections in childhood might make a future diagnosis of autism spectrum disorder more likely in men who are genetically predisposed to the condition.   

Scientists at the University of California, Los Angeles performed the study on mice, so it’s too early to say what its implications are for humans. But other research hints at a similar association: Data collected by researchers at the University of Chicago and used in the same new study found that boys diagnosed with autism were more commonly hospitalized with infections between the ages of 1.5 and 4 than boys who didn’t have autism. (That dataset included more than 3.6 million children with a host of different infections, though the UCLA study didn’t explore whether any particular virus was associated with autism.)

“These parallels are so striking that they’re highly unlikely to be unrelated,” Alcino Silva, director of UCLA’s Integrative Center for Learning and Memory, said of the mouse and human data.

The research bolsters the idea that genetic factors don’t necessarily trigger autism on their own. Environmental factors, like a viral infection, also play a role.

The mouse study even offers a possible explanation as to why: Childhood infections may cause the body to over-express genes that code for microglia, the central nervous system’s primary immune cells. That, in turn, can affect brain development, which could be at play in some traits commonly associated with autism, such as difficulty communicating verbally or recognizing familiar faces.

So the researchers experimented with drugs that target microglia, and found that they not only prevented those social issues in adult mice — they might have reversed them.