A deadly mosquito-borne virus that can spread to and kill humans has been detected at two Queensland pig farms.

A fresh alert for Japanese encephalitis virus (JEV) has been issued for Queensland residents after the serious mosquito-borne disease was detected in the state's south.

highlights the risk of JE virus infection in a large stretch of NSW west of the Great Dividing Range,” NSW Health’s Executive Director of Health Protection Dr Jeremy McAnulty said.