Rugby league players could face months of being in and out of quarantine with leading swine flu authorities on Wednesday warning they risked contracting the virus every time they travel to play games.

As NRL clubs began clearing their representative players to return to action this weekend, senior World Health Organisation official Ian Barr predicted rugby league and all sport would eventually be hit by swine flu or other flu viruses.

"It won't just be the Broncos or rugby league clubs, it will be all sporting activities that will be compromised or their sporting schedule interrupted," said Barr, deputy director of WHO's influenza centre in Melbourne.

"The players are all susceptible, especially if they are sitting next to somebody on a plane for a few hours."

A number of rugby league's leading players have been quarantined since Queensland State of Origin forward Ben Hannant became the sport's first swine flu victim.

Friday night's NRL blockbuster between Brisbane and the Bulldogs remained under threat late on Thursday as Brisbane officials anxiously awaited test results on fullback Karmichael Hunt, believed to have contracted swine flu in Melbourne last week.

"It's likely to be a recurring problem for rugby league players who are constantly exposed to new environments," Professor Anton Middelberg, an expert on vaccines and flu vaccination with the University of Queensland's Australian Institute for Bioengineering told AAP on Wednesday.

"I think you'll find players will have to be re-tested and that the situation could worsen as we enter the peak flu season in particular."

Health officials are currently employing a containment program, treating players displaying swine flu symptoms with tamiflu, which is an anti-virus, not a vaccine, and placing them in quarantine for 72 hours.

"The idea is to try and stop the spread and limit its pervasion into society," said Professor Middelberg.

"We're very fortunate that so far we haven't seen any deaths.

"But there are people who are susceptible because of underlying health problems which I suspect aren't going to be our rugby players.

"But invariably those guys do come in very close contact with a diversity of fans."

Hannant can consider himself the safest player in rugby league because according to experts swine flu is a once only virus.

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