Nigerian government officials and the World Health Organization (WHO) reported that the cause of the suspicious deaths in a small town in Ondo State of Nigeria was due to herbicide poisoning.  

The "current hypothesis is cause of the event is herbicides," WHO spokesman Gregory Hartl wrote in a tweet. 

"Tests done so far are negative for viral and bacterial infection." 

The outbreak started on April 13 affecting individuals between the ages of 25 and 60 affecting 13 individuals. Officials say the disease does not appear to be contagious at this time, thus keeping the mortality total to 18. Five others are receiving treatment at the University of College Hospital, Ibadan. The affected individuals reported having symptoms including headache, blurred vision, blindness, and unconsciousness. 

There is suspicion that the illnesses may be the result of contamination of locally brewed alcohol. According to the WHO, doctors plan to conduct tests at the Lagos University Teaching Hospital on one victim who died in a hospital. 

Officials from the world health body have visited Irele town, the state Health Commissioner, Dayo Adeyanju, said. Adeyanju reports that some people accidentally consumed an alcoholic drink mixed with local herbs not knowing that the drink was poisonous and contained methanol. He says the government is creating awareness on why people should stop taking gin mixed with local herbs, and advises residents to stop drinking the local gin, Ogogoro.

References:

Nigeria mystery deaths: Pesticides suspected, says WHO - BBC News. (n.d.). Retrieved April 22, 2015, from http://www.bbc.com/news/world-africa-32372502

'Mystery' disease confuses health officials in Nigeria - AOL.com. (n.d.). Retrieved April 22, 2015, from http://www.aol.com/article/2015/04/20/mystery-disease-confuses-health-officials-in-nigeria/21174096/