New South Wales Blues reserve Nicho Hynes has tested positive to coronavirus, ruling him out of both State of Origin camp ahead of the decider in Brisbane next Wednesday, and the Cronulla Sharks' clash with the Melbourne Storm on Thursday evening.

In his place, the Blues have called in-form North Queensland Cowboys' half Chad Townsend into camp ahead of the decider.

The news was confirmed by Origin head coach Brad Fittler on 2GB Radio on Wednesday evening.

While Townsend is unlikely to play, and would need multiple injuries to come into contention for the Blues, his experience in camp could be invaluable, as could his knowledge on a host of Queensland Cowboys - with all of Valentine Holmes, Murray Taulagi, Jeremiah Nanai and Tom Gilbert picked for the men from north of the Tweed, while Tom Dearden and Hamiso Tabuai-Fidow are also on the reserves list.

Hynes, who was named as 18th man for Games 1 and 2 of the series, was demoted to 19th man for the decider thanks to Jack Wighton's return.

It meant he was supposed to play for the Sharks this evening against the Melbourne Storm, however, he has been ruled out of that clash with Braydon Trindall to come into the side.

Toby Rudolf has also been ruled out for the Sharks, allowing for the return of Braden Hamlin-Uele from injury, with the big forward to play from the bench.

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Hynes was in camp on Monday before returning to Cronulla training, however, at this stage, no other New South Wales player has tested positive for the virus.

It's understood all Origin players in both states' camps are being tested twice per day in an effort to ensure the virus doesn't wipe out the decider, with rules still stating that players must quarantine for a minimum of seven days after contracting the illness.

Townsend has been in wonderful form for the Cowboys, recording 14 try assists and 10 forced drop outs in 16 games.