Eight people have died from cholera in Garissa and neighbouring Madogo division of Tana River county.
Health Chief Officer Mohamed Farah said on Wednesday that 290 people had been diagnosed and treated in two weeks.
“Over 90 per cent of all the cases at the Garissa County Referral Hospital isolation unit are from Tana River. We suspect residents are using contaminated water."
Farah added the disease may have been spread by casual workers from Madogo who go to the town on a daily basis to eke out a living.
The official said the department had taken measures including treating water sources in affected areas.
Health workers were sent to Tana Bridge to disinfect residents crossing over and commercial vehicles from Madogo area to prevent the spread of the disease.
Owners of open-air eateries and butcheries were ordered to close them.
Farah advised residents to maintain high standards of hygiene even after the cases are dealt with.
He asked them to immediately take anyone with symptoms such as diarrhoea, headaches and weak joints to isolation centres in Sankuri, Fafi and Mbalambala, as well as Madogo health center and the referral hospital.
Farah ruled out the possibility that last year’s cholera outbreak could have originated from the vast Dadaab refugee camp.