SHANGHAI – Juan Martin del Potro said he is suffering from a virus and reviewing his health "hour by hour", after labouring into the Shanghai Masters last 16 on Wednesday. The Argentine world No 4 lost Sunday's final of the China Open in Beijing to unseeded Nikoloz Basilashvili and afterwards revealed that he had been unwell. Three days on and he continues to be under the weather, but just about did enough to see off France's Richard Gasquet in Shanghai, 7-5, 7-6 (9/7). Alexander Zverev has also a sore throat and blocked nose. Del Potro said: "It wasn't easy to play for me today, I did what I can. I didn't run too much. "But of course I would love to feel better, first of all to myself, and then to play tennis, but it's going to be difficult because I'm not taking time to recover 100 percent."