There are growing fears NRL, AFL, Super Rugby and A-League matches will either be played in empty stadiums or cancelled altogether after a man with coronavirus attended last weekend's Melbourne Rebels match.

The man - who did not know he had coronavirus at the time he sat in the lower bowl at AAMI Park in Melbourne and watched the Rebels beat the Lions - was confirmed as one of three people diagnosed in the city on Wednesday morning, taking the total number of cases in Victoria to 21.

A coronavirus-infected fan attended the Rebels-Lions clash at AAMI Park on Saturday. Getty

The Olympic Park Trust confirmed the man had attended the match on Saturday night. While the next match at the venue - an A-League clash between Melbourne City and the Western Sydney Wanderers - will go ahead, the lower bowl will be intensively cleaned.

"Department of Health and Human Services has advised that the patron who attended AAMI Park for the rugby union match between the Melbourne Rebels and the Lions was diagnosed with COVID-19 overnight," an Olympic Park spokesperson said.

"The patron sat in section nine on the east side of the venue. The case has been classified by DHHS as low-risk of spreading COVID-19 to surrounding members of the public and staff.

"DHHS recommends that those who were seated in section nine can go about their regular activities, but to monitor their health and remain mindful of their hygiene practices.

"As a precautionary measure, M&OP have initiated intensive cleaning of AAMI Park today and will follow a rigorous cleaning regime over the next week. During this time, M&OP will continue to work closely with the government and health authorities."

The news of the first fan to be diagnosed with the deadly virus comes as NRL, AFL, Super Rugby and A-League clubs continue to prepare contingency plans should a player or staff within the organisation become infected.

Some clubs are already privately resigned to the reality of playing in empty stadiums or fixtures being cancelled altogether.

The Sunwolves played their last home game against the Brumbies at WIN Stadium in Wollongong and will face the Crusaders at Suncorp Stadium on Saturday and a club source said they are now unlikely to take on the Reds in Tokyo on April 5, either.

SANZAAR nations will hold a conference call to discuss the outbreak on Wednesday night.

"The SANZAAR CMOs [chief medical officers] continue to meet on a weekly basis to assess the information from the relevant health authorities in each country and continue to update advice on key preventative measures and planning considerations in relation to the virus, for the benefit of each union and its players, match officials, medical teams, and support staff involved in Super Rugby," a Rugby Australia statement said on Wednesday.

"Two of the Japan-based Sunwolves’ matches have been relocated to Australian venues after the Japanese government’s ordering of the cancellation of major sporting events in the country through early March.

"Discussions are ongoing at SANZAAR and with the Sunwolves in relation to future matches scheduled for Japan, with the team continuing to be based in Australia ahead of its match against the Crusaders in Brisbane on Saturday."