Andy Murray, of Britain, returns the ball to Fabio Fognini, of Italy, during the Italian Open tennis tournament, in Rome. Photo: Andrew Medichini/AP

World number one Andy Murray said Friday he considered himself lucky despite seeing his season torpedoed by shingles, flu, an elbow injury and now a pre-French Open fever.

Murray, the 2016 runner-up at Roland Garros to Novak Djokovic, admitted he had been sick since arriving in the French capital on Sunday.

"I felt sick in the afternoon and didn't feel great on Monday but I feel better. Now it's just a cough," said the 30-year-old British star who thinks he caught a bug training in the wet and cold of London earlier this month.

Murray's poor form this year has, not surprisingly, reflected his physical travails.

He suffered a shock fourth round defeat to Mischa Zverev at the Australian Open.

On clay, he lost in the third round in Monte Carlo, made the semis in Barcelona, was a third-round loser in Madrid before an opening defeat in Rome to Fabio Fognini.

"It's frustrating – it's the third time I have been ill this year," he admitted.

However, he said he was surprised that he hadn't been laid low by sickness on many more occasions over his career.

"To be honest, it should happen more really. We are in the locker rooms with lots of players, lots of sweat, lots of germs, you know, in airplanes all the time.

"I have been pretty lucky with that over the last couple of years. I have not had too many bad illnesses. So maybe they have just come in a small space of time."

Murray has been drawn to face 2015 champion Stan Wawrinka in the last four at this year's Roland Garros.

He starts against Russia's world number 85 Andrey Kuznetsov and could face dangerous Juan Martin del Potro in the third round.

Injury-plagued del Potro, who lost to Murray in the 2016 Olympics final, is playing Roland Garros for the first time since 2012 when he made the quarter-finals.

If the seedings work out, Murray would face Japan's Kei Nishikori in the last eight.