The Lamu Public Health Office on Thursday reported an outbreak of amoebic dysentery, infecting more than 100 people.
It is spreads through drinking or eating uncooked food, such as fruit that may have been washed in contaminated water, or drinking contaminated water.
Officials denied rumours of a cholera outbreak in Lamu.
"It's not cholera but amoebic dysentery. Both have similar symptoms," Public Health director Athman Dumila said.
Amoebic dysentery is a parasitic infection of the colon and is most common in tropical areas with untreated water.
Symptoms include diarrhoea, cramping, bloody stools, vomiting, fever and in the worst cases liver infections.
Dumila said many cases were reported in May and June.
Speaking in his office, he said they suspect the outbreak is caused by consumption of dirty water during this rainy period.
He said they also believe the outbreak is worsened by the many flies in the region since the rains began.
Residents have been advised to practice good hygiene in their environments and to wash their hands and food in clean water.
They have been urged not to buy ready-made food on the streets as it may be infected. A lot of street food is not covered and may be infected by flies.
Anyone with major symptoms of diarrhoea and vomiting should go to a hospital.
“There is that outbreak but we can do something to stop it," Dumila said.
"Cook in your house and eat there. Use insecticide where possible. Cover flood and keep flies away and don't use dirty rainwater," he said.
Free insecticide is being distributed to all homes, markets and public places to kill flies.
Public sessions will be held on personal and environmental hygiene.
(Edited by V. Graham)
