Cycling Australia announced the news Saturday morning.
"I'm really disappointed to miss the road race. It was a big goal for me at the end of the season and I had been training and racing with the road race in mind.
"However, recent illness means my preparation has been far from ideal and for a race of this difficulty, with more than 4600 metres of climbing, you need to have the best preparation possible to be up there.
"Within the Cycling Australia team, we have decided that it is in the team's best interests if my place goes to someone else. I wish the whole Aussie team the best and will be cheering them on from home."
Porte's trade team doctor, BMC Chief Medical Officer, Dr. Max Testa said he developed an upper respiratory infection in the final week of the Vuelta a España which he was riding in preparation for the world championships after his disastrous exit from the 2018 Tour de France on Stage 9.
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"(It) has required him to take antibiotics and stop training. He will need a few more days off the bike to recover properly which means it does not make sense for him to line up at the Worlds Championships. Richie will resume training next week and will be able to race again this season," said Testa.
Australian Cycling Team performance director Simon Jones said the team will regroup and focus during the week ahead. Cycling Australia is considering its options regarding a replacement.
