Pritchard won the Challenge Cup with Hull during his sole season in the Super League but 'Frank the Tank' is more well known for his impressive stints with Penrith Panthers and Canterbury Bulldogs before arriving in the UK.
The 38-year-old contracted Covid-19 over Christmas and was also admitted to the ICU at Liverpool Hospital in Australia, according to the Daily Telegraph.
Pritchard is said to have 'long battled with asthma problems and previously suffered from lung complications'.
“We’re all praying for him, that he gets better and back to his family,” player manager Mario Tartak told the Daily Telegraph.
The former dominant forward retired from rugby league at the end of the 2017 season following a campaign with Parramatta Eels in the NRL after his return to Australia. Pritchard also starred for New Zealand and Samoa on the international stage.
Rugby league legend and NRL commentator Phil Gould has tweeted his support for Pritchard amid the Covid-19 news.
Gould tweeted: "Hearts and prayers are with former Bulldog Frank Pritchard who is in hospital battling Covid. We send all our best wishes for a full and speedy recovery. Our love to Frank’s family and friends."
Since retirement, Pritchard has been involved in coaching the Samoan national team and youth development in Australia.
Pritchard opened up on his retirement in 2017 and explained on social media: “Thank you to all the clubs that allowed me to live my dreams. From a young kid from Claymore I always dreamed of being where I have been for the past 15 years, that dream came true.
“I’m truly grateful for what the game has given me, from this I will take away so many life experiences and memories to last me a lifetime. This isn’t the end but a new beginning of a new chapter.
“There’s a couple things I want to do. I had a coffee shop before leaving to play in England, so the plan is to open up another one. The main priority is the coffee shop, but to also do some welfare work with troubled kids and work with youth.
“I also want to stay involved with footy and maybe coach some Junior League. I want to thank the Eels for the opportunity to let me play and I’m truly honoured and grateful to play in the Blue and Gold jersey.”