( CNN ) A mysterious affliction has killed as many as 18 people in southwestern Nigeria , leaving health officials scrambling to determine its cause . The cases have all occurred in Nigeria 's Ondo state since April 13 , health officials said Sunday . Dr. Dayo Adeyanju , Ondo 's state commissioner for health , said 18 people have died and five people are being treated . Those affected are between the ages of 25 and 60 . The disease does not appear to be contagious , he said . Symptoms include headaches , blurred vision , loss of sight and unconsciousness , Adeyanju said . Some suspect it may be the result of locally brewed alcohol . The World Health Organization , earlier Sunday , reported at least 13 people were killed and that there were 18 total cases . Those numbers were reported by Adeyanju released somewhat different totals . Investigators sent samples of blood , urine and spinal fluid to a university in the city of Lagos for tests , which ruled out infections from viruses or bacteria , the WHO said . Doctors plan to carry out toxicological tests on one of the victims who died in a hospital , WHO spokesman Tarik Jasarevic said .
18 dead and 5 being treated , Nigeria says . Locally brewed alcohol is suspected . Some patients have died within hours .