The 'Rocket' has been back to his best in recent weeks, winning the German Masters and only defeat to world number one Mark Selby denied him a place in the Welsh Open final.
But, having played in those tournaments against his doctor's advice, fatigue has caught up with the three-time world champion.
The 36-year-old said: "I am very sorry. Despite my illness I have been competing well in recent weeks and was greatly looking forward to taking part in the World Open and meeting my fans in China.
"However, I have to listen to my body sometimes and I have decided that I will be in better shape for the climax of the season and the World Championships if I listen to my doctor and spend the next few weeks resting.
"I hope I can make it to Ireland and China in March and look forward to seeing you all soon".
O'Sullivan fell one place to 14th in the latest rankings but has still avoided the World Championship qualifiers after his efforts in Newport kept him in the top-16.