Gulbis, Knocked Off Course by Malaria, Fights Her Way Back on Tour After a strong start, Natalie Gulbis fell back in the second round of the United States Women's Open. SOUTHAMPTON, N.Y. - Her caddie, Greg Sheridan, was the first to grow alarmed at her growing list of symptoms. Something seemed definitely off about Natalie Gulbis's condition. They were in Sentosa, Singapore, in the first round of the HSBC Women's Champions tournament at the end of February, and after Gulbis dragged her way through 75 shots, tired and delirious, Sheridan voiced his concern. He drove Gulbis to the emergency room. "I had a fever of about 107," Gulbis said. In Singapore, doctors treated her for flulike symptoms, and she returned to the United States feeling well enough to think she might be able to play in the Kia Classic in Carlsbad, Nev. After a practice round, she returned to the hospital, unable to shake her fever. Blood tests revealed a diagnosis she never could have imagined: malaria. "It was kind of a freak thing," Gulbis said Friday at the United States Women's Open at Sebonack Golf Club, where her second-round effort was suspended after the 13th hole because of fog. Gulbis is one of the L.P.G.A. Tour's most popular players - better recognized for her off-the-course résumé - but she turned in a two-under-par 70 in the first round Thursday, four strokes off the lead. She struggled early in her second round Friday, dropping five strokes on the front nine as she struggled with her putting and her midrange game. When play resumes Saturday morning, Gulbis, at three strokes over par, will trail the leader, Inbee Park, who shot a 68 on Friday, by 12 strokes. But for Gulbis, competing at Sebonack at all is something of a blessing, with how the first months of her season unfolded in March and April. Malaria kills more than 600,000 people a year, the majority in Africa, but it is a relatively uncommon infection for Americans, and often easily cured once the symptoms are properly diagnosed and following a typical incubation period lasting 8 to 25 days. Doctors determined that Gulbis picked up the disease from a mosquito bite during the Honda L.P.G.A. Thailand tournament the previous week. A frequent traveler, Gulbis said she had never really worried much about the disease. What followed were rounds of medication, intravenous therapy and days in a hospital bed. She lost 15 pounds and went through bouts of listlessness, then days full of energy, then more dips in vigor, a relentless cycle as the medication and the infection worked their course. "Mentally, you think you can do more," Gulbis said. Then I would practice a little bit more, and that would set me back. Then I'd have to start again. She tied for 32nd in the Kraft Nabisco Championship in early April after shooting a 74 in the first round and requiring an IV to replenish her fluids. A month later, she missed the cut at the L.P.G.A. Championship, carding a 78 in the first round. But Gulbis said it was the first time she had truly begun to feel like herself again. That was two months after the initial mosquito bite. "They told me it was going to be six weeks, but I have an athlete's mentality that I thought I could come back sooner," Gulbis said. They were right. Gulbis attracted a large following Thursday and Friday, which is not unusual. She has a number of offbeat career highlights, including posing in the 2012 Sports Illustrated swimsuit issue, starring in her own reality show on the Golf Channel, dating Pittsburgh Steelers quarterback Ben Roethlisberger, and appearing on the reality show "Celebrity Apprentice," the game show "The Price Is Right" and the television drama "C.S.I." Her lone L.P.G.A. victory, at the Evian Masters tournament, came in 2007, but Gulbis played as if she might work her way into contention on Thursday in just her ninth tournament of the year. Gulbis said she had felt in peak condition for three weeks. With Sheridan, her caddy for the past nine years, she found herself on the leader board after Day 1 but slipped into a tie for 32nd before play was suspended Friday. Gulbis said her illness had not reshaped her outlook on much, and that she would not hesitate to return to Asia for another set of tournaments next season. "I've gotten sick and injured before from traveling," she said. The thing I'm always reminded of is how lucky I am to have great friends and family to care about me.