Microbes' roadmap to neurons.

The nervous system is protected by barriers that restrict the invasion of pathogens. Nevertheless, mechanisms have evolved by which microbes can pass these barriers, enter and exit neurons and target various regions of the nervous system. In the brain, immune responses to pathogens are generally not robust, so microbes can hide and survive or, conversely, cause severe uncontrolled infections. Depending on their sites of entry and the regions that they target, microbes can cause diverse nervous system dysfunctions and even influence host behaviour to their own advantage. This Review discusses routes by which microbes can reach the nervous system and cause persistent or life-threatening infections.