Doctors do not know the cause of the illness but say the disease progresses rapidly to the renal system and causes neurological damage.
The dead were all over 60 years of age and most were already suffering from high blood pressure, diabetes and kidney problems.
Three suffering from the unidentified illness died late yesterday in Panama City and another 12 deaths over the past month have been confirmed to have been caused by the same disease, the ministry said.
The ministry has declared a national epidemic alert.
The illness did not seem to be contagious and dengue fever, influenza, West Nile virus had been ruled out.