The Covid cluster in the Australian swim team may be worse than first feared, after Tokyo champion Zac Stubblety-Cook revealed he swam through an infection to win silver in the 200m breaststroke on Wednesday night.

In a post on Instagram, the 2023 world champion expressed his pride at finishing second despite recent hardships.

“I could not be prouder,” said Stubblety-Cook. “The last 6–12 months have been nothing but a wild ride full of highs and lows! To come back from breaking my neck end of last year to multiple cortisones, starting a coffee business and now dealing with Covid.

“The emotions of all these trials and tribulations, combined with the looming pressure of defending my Olympic title, has been nothing short of a continuous roller coaster, full of doubt, and hardship,” the Australian added.

In a statement, the Australian Olympic Committee confirmed that Stubblety-Cook had completed a five-day course of antivirals for the illness on Wednesday.

The news comes two days after fellow Dolphin Lani Pallister withdrew from the 1500m freestyle with Covid, citing a desire to rest in the hope of returning for the women’s 4x200m freestyle relay on Thursday.

Guardian Australia understands that the swim team have deployed the usual Covid precautions, including mask-wearing in busy areas, but have not introduced new measures as a result of the two infections.

Several other nations have been hit by Covid at the Games swim meet, including British legend Adam Peaty.

Peaty tested positive for Covid on Monday, less than 24 hours after being denied a historic golden treble when he was beaten to the 100m breaststroke gold by 0.02sec. The British Olympic Association remains optimistic Peaty will recover in time for the 4x100m medley and 4x100m mixed medley this week as he seeks to add to his six Olympic medals.

Stubblety-Cook also paid tribute to his rival, home favourite Léon Marchand, who won the breaststroke less than two hours after securing the 200m butterfly gold medal – a historic double.

“Experiencing a race with [Marchand] in front of a home crowd at the Olympics, memory I’ll cherish forever,” wrote Stubblety-Cook.

Australia will be looking to add to the medal haul at the Olympic swim meet on Thursday, with the 4x200m relay team highly favoured to win gold.