Serena Williams will be fit to defend her US Open title after recovering from the virus which ended her Wimbledon.
The world number one, 32, was forced to pull out of her doubles match with sister Venus earlier this month after struggling to serve.
But she makes her return at the Bank of the West Classic at Stanford University on Wednesday and will be ready for the US Open when it starts on 25 August.
She said: "I feel very good. I feel very happy to be here, so it's good."
Williams was beaten in the third round of the singles at Wimbledon by France's Alize Cornet, before retiring from the doubles a few days later.
|Serena in Slams|
|Serena Williams won her first Grand Slam in 1999 when she beat Martina Hingis in the US Open final.||She has won 32 Grand Slam titles in total, with 15 coming in doubles.|
|She has won 17 Grand Slam singles titles - sixth on the women's all-time list.||She has lost just four of her 21 Grand Slam singles finals - most recently to Samantha Stosur at the 2011 US Open.|
She struggled in the warm-up and needed treatment from the doctor before serving four straight double faults in the third game.
"They just said I was really ill, and really under the weather and I just wasn't doing very well," Williams said.
"I was really scared after because I didn't realize how I felt until later and it's just, you know, 'Serena, keep your time, you will have the rest of your life to keep playing tennis hopefully.'
"I didn't leave my house or my bed for a few days."
Williams, who has won at least two majors in four of the past five years, has not won one this season.
She made a fourth-round exit at the Australian Open, was beaten in the second round of the French Open and lost to Cornet in the third round at Wimbledon.
She has won the US Open on five occasions, including the last two.