Which is the most common virus in the US that can cause encephalitis?

The most common virus in the U.S. that can cause encephalitis is the herpes simplex virus (HSV), particularly HSV-1. This virus can lead to significant inflammation of the brain and is often associated with severe neurological outcomes. Other viruses, like West Nile virus and Eastern equine encephalitis virus, can also cause encephalitis, but HSV remains the most prevalent cause.