NSW Health revealed details of the latest case, a man aged in his 50s from the Temora area, yesterday.

The man was treated in hospital, but has been discharged. He is continuing to recover in the community.

Murrumbidgee Local Health District director public health Tracey Oakman said yesterday most of the eight NSW Japanese encephalitis patients had been unwell in February.

"It does take some time for the testing results to be confirmed," she said.

"We are investigating more cases and potentially there are more cases."

Ms Oakman said vaccines were being offered to people like those who work with mosquitoes, at piggeries or in certain laboratories.

"There is limited supply and we are targeting those at-risk groups currently but that will be broadened as more vaccine arrives into the country," she said.

"More supplies have been ordered and are expected to arrive in April."

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Mosquito numbers are likely to decrease as the weather grows cooler.

"That will give us a reprieve, what we don't know is what's going to happen next year," Ms Oakman said.

"It is unlikely that this virus will disappear and so that vaccination program will be important to set us up for future summers."

The Department of Primary Industries is conducting further tests at piggeries to determine the spread of Japanese encephalitis.

"The virus may have got into other animals and so there are studies being set up so we can try and find the length and the breadth of where the virus may have been and how long it may have been around," Ms Oakman said.

Six cases of JE have so far been recorded in the Riverina - with the Temora case adding to two in Griffith, one in the Berrigan area, one in Corowa and another in the Balranald area.

One of the Griffith cases, a man in his 70s, was the state's first death with JE. He died in a Sydney hospital on February 13.

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