The widespread viral infection at Indian Wells claimed two big names on Monday as former French Open winner Francesca Schiavone and Wimbledon champion Petra Kvitova both pulled out.
Italian Schiavone, who won her only grand slam singles title at Roland Garros in 2010, withdrew during her third-round match in the WTA tournament when trailing Czech Lucie Safarova 2-6.
Czech Kvitova, who had already been ousted as the third seed from the singles draw on Sunday, pulled out of her women`s doubles match on Monday citing a stomach bug.
According to officials, eight players have withdrawn from the tournament because of the virus, which local health authorities have described as a 48-hour bug transmitted by air and direct contact and not via food.
"I have had it before a few years ago and it`s not pretty," Russian Maria Sharapova told reporters after booking her place in the fourth round with a 6-3, 6-4 win against Romania`s Simona Halep on Monday.
"It`s a great diet, but other than that it`s horrible, especially for an athlete. But it`s pretty tough, considering you can`t really escape it too much."
Fellow Russian Nadia Petrova, who upset sixth-seeded Australian Sam Stosur 6-1, 6-7, 7-6 in the third round on Monday, said she was closely following the advice of the local health authorities.
"I`m definitely washing my hands as much as possible," the 29-year-old added. "I`m going to have a sanitizer in my racquet bag. I`m trying to eat off-site, so trying to take as many precautions as possible."
Among the players who have already succumbed to the stomach bug at Indian Wells are Frenchman Gael Monfils, who exited the ATP tournament on Sunday, and Germany`s Philipp Kohlschreiber, who withdrew last week.