Italian Vincenzo Nibali dropped out of the Vuelta a San Juan before the start of stage 1 after contracting gastroenteritis before the race began, the Bahrain-Merida team announced on Twitter on Sunday.
After 100km, another rider from the team, newcomer Mark Padun, also left the race with the virus. The four remaining teammates will go on without him, with Nibali's brother Antonio joined by Kanstantsin Siutsou, Niccolo Bonifazio and Ivan Cortina.
There were reports of more riders being hit by the bug at the race hotel, and there could be more abandons as the race continues. The Vuelta a San Juan opens with a 148.9km stage from San Juan - Pocito on Sunday.
It is an inauspicious start for Nibali, who ended last season with a victory in Il Lombardia after coming second to Chris Froome (Team Sky) in the Vuelta a España. Nibali could stand to inherit that title from Froome should the Briton be disqualified for his too-high salbutamol level on stage 18 of the race.
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