David Ferrer of Spain, ranked fifth in the world, retired from his first-round match Tuesday in Beijing at the China Open, stopping his match against Lu Yen-Hsun of Taiwan at 5-4 in the first set. The reason for Ferrer’s midmatch retirement, his first such forfeit since 2009, was listed as a stomach virus.

The New York Times reports Ferrer’s retirement came one day after 24th-ranked Anastasia Pavlyuchenkova of Russia retired in the third set of her first-round match against Polona Hercog of Slovenia, a qualifier, citing a G.I. illness.

Though only the second Chinese tournament of the year, the China Open is not the first to be troubled by such problems, perhaps not surprising given China’s heavily scrutinized record on food safety.

Two weeks earlier at a W.T.A. tournament in Guangzhou, there were three exits attributed to gastrointestinal illness. Top-seeded Marion Bartoli of France retired in the first set of her first-round match, then Olga Govortsova of Belarus retired after losing the first set of her second-round match against Alize Cornet of France. Later that day, it was Cornet who withdrew from her doubles match because of gastrointestinal issues. Alexandra Panova of Russia and Yung-Jan Chan of Taiwan also withdrew midway through matches in Guangzhou, citing the possibly stomach-exacerbated issues of “heat illness” and “dizziness.”

Though the aforementioned are confirmed examples of stomach issues forcing players out of competition, it is difficult to determine. Since there is little risk of long-term damage from playing through digestive discomfort compared to a joint or muscle injury, the incidence of players who decide to soldier on is likely a much higher percentage than for other afflictions.