A South Australian man has died from the mosquito-borne virus Murray Valley encephalitis (MVE).

The man, 27, from the Riverland in South Australia had been in hospital since March.

He was one of two confirmed cases of MVE in South Australia, the first reported to have been locally contracted since 1974.

The other confirmed case was in a man, 47, who now has been released from hospital.

The disease is spread by mosquito bites and most people have mild symptoms.

A wetter summer led to a sharp rise in the number of mosquito-related cases of illness in South Australia.