The 30-year-old has been advised not to travel after being admitted to hospital with the disease at the weekend.
A statement on the club's official website said: "The Togo international was admitted to hospital on Saturday after reporting feeling unwell to our medical staff. A swift diagnosis meant the disease was detected at an early stage and he is responding well to treatment.
"The striker is expected to be released from hospital tomorrow and will then require a minimum of seven days before returning to training. The player has been advised not to travel on medical grounds, which means he will be forced to miss our pre-season tour of North America."