The food Mukumu girls high school students consumed was contaminated with fresh faeces, the Ministry of Health has said.
Director General for Health Patrick Amoth made the revelation in In a statement on Friday.
"The Ministry wishes to inform the general public that this disease is likely to be a mixture of E. coli and Salmonella typhi which usually occurs if water sources are contaminated with these micro-organisms," he said.
Escherichia coli (E. coli) is a bacteria commonly found in the lower intestine of warm-blooded organisms that can cause food poisoning.
Salmonella enterica typhi is a gram-negative bacterium that is responsible for typhoid fever.
Amoth added that further laboratory investigations carried out on the grains and pulses for aflatoxin turned negative for aflatoxicosis.
"Laboratory tests for Viral Hemorrhagic Fevers (VHFs) including Ebola Virus Disease (EVD), Marburg Virus Disease (MVD), Leptospirosis and Crimean- Congo Hemorrhagic Fever (CCHF), Dengue Fever, Rift Valley Fever (RVF) and West Nile Virus have all turned negative," he said.
"The Ministry is conducting further analysis on these samples to ascertain any other potential cause of this illness, and will communicate the finding of these tests."
Amoth added that the disease presents fever, abdominal pain/cramps, vomiting and diarrhoea.
He said comprehensive investigations are currently underway but data analysed so far indicated that the disease seems to have started on March 1, 2023.
The DG said that as of April 14, 627 patients had been taken ill while 19 students are currently admitted to seven health facilities across the country.
He said those admitted are in astable condition.
Amoth added that four patients have died from the illness. The four include three students and a teacher at Mukumu Girls School.
"We at the Ministry of Health send our heartfelt condolences to the families who have lost their loved ones," he said.
He said the two schools have since closed as further investigations continue.
Amoth said the Ministry dispatched an investigation team on April 1, 2023, from the National level to support the Kakamega County team.
"The team was further backed by a high-level visit of a multi-agency team led by the Cabinet Secretary for Health, and included the Principal Secretary for the State Department of Basic Education, the Governor of Kakamega County, Western Regional Commissioner and the County Health, Education and Security teams."
The ministry called on the public to maintain high standards of personal hygiene by washing hands with soap and running water, treating or boiling all water for drinking and cooking.
Kenyans have been urged to use toilets to safely dispose feces and to properly cook all food and eat it while still hot.
"We appeal to the public to be vigilant, and requests that anyone experiencing fever, abdominal pains/cramps, diarrhea and vomiting to seek immediate treatment at the nearest health facility for assessment and prompt management," he said.