(Reuters) - Latvian 11th seed Anastasija Sevastova exited the BNP Paribas (PA:BNPP) Open with a viral illness in Indian Wells, California on Monday.
Sevastova was down 5-0 in the first set of her third round match with Estonian 21st seed Anett Kontaveit when she retired.
Her departure, the cause of which was reported by the WTA, came less than 24 hours after Serena Williams (NYSE:WMB) was unable to continue her match on Sunday, also citing a viral illness.
Men's third seed Alexander Zverev revealed on Monday that he too had a virus, speaking after losing to fellow German Jan-Lennard Struff.
Among those women still feeling healthy, three-times grand slam champion Angelique Kerber battled back to beat Russian qualifier Natalia Vikhlyantseva 3-6 6-1 6-3.
Kerber took a while to warm to her task on a cool morning in the California desert.
"She was playing really fast and flat, so that was something I was not really expecting," the German said of her opponent.
"I was trying to adjust, especially with my movement at the end of the first set and beginning of the second, and I think that was the key to coming back."
Another high seed, No. 5 Karolina Pliskova, was not at her very best but still prevailed 6-3 6-2 over Ysaline Bonaventure.
"I felt somehow strange and the match was strange," said former number one Pliskova.
The Czech has made a fine start to the year, winning the WTA event in Brisbane and reaching the Australian Open semi-finals.