Alexander Zverev and Anastasija Sevastova became the latest players to be hampered by illness during third-round exits at Indian Wells on Monday.
On Sunday, Serena Williams retired from her third-round match, citing "extreme dizziness and extreme fatigue".
A day later, Sevastova pulled out when 5-0 behind to Anett Kontaveit with the WTA saying she had a "viral illness".
Men's third seed Zverev also said he had a virus after losing to Jan-Lennard Struff.
Zverev was beaten 6-3 6-1 by fellow German and world number 55 Struff.
"I have been sick for a week. That hasn't changed unfortunately," the world number three said.
"I think I just got unlucky, got a virus somewhere and that's how it is.
"Now it's about getting healthy and about recovering and preparing myself for Miami, because Miami is a tournament I do well in."
Osaka and Williams progress
Elsewhere, defending champion Naomi Osaka comfortably progressed to round four by beating American Danielle Collins.
The Japanese world number one had her serve broken early but recovered, hitting 29 winners en route to a 6-4 6-2 victory.
Osaka will play Belinda Bencic next after the Swiss beat Ekaterina Alexandrova 6-4 6-2.
American Venus Williams also progressed with a 6-2 7-5 win over qualifier Christina McHale.
The 38-year-old, who beat Petra Kvitova in the last round after being a set and a double break down, lost the first game on serve but won the next five to take the first set and came from 3-1 down in the second to win in an hour and 25 minutes.
Williams will face world number 97 Mona Barthel, who beat Julia Goerges.
Three-times Grand Slam champion Angelique Kerber battled back to beat Russian qualifier Natalia Vikhlyantseva 3-6 6-1 6-3.
Fifth seed Karolina Pliskova beat Belgian Ysaline Bonaventure and ninth seed Aryna Sabalenka won against Lesia Tsurenko.
In the men's draw, world number one Novak Djokovic's third-round match against German Philipp Kohlschreiber was suspended due to rain with the Serb leading 1-0 in the first set, meaning the pair will return later on Tuesday.
Milos Raonic reached the fourth round after the Canadian battled back from a break down in the decider to beat American qualifier Marcos Giron 4-6 6-4 6-4.
Dominic Thiem, Ivo Karlovic and Gael Monfils also progressed.