The number of Nairobi Hospital staff infected with cholera has risen to 52.
Mr Tom Simba, the hospital's communication officer, said on Thursday that every staff member on duty when the disease was reported has been tested.
The outbreak hit the hospital on Tuesday, leaving one staff member dead and several others admitted.
The male worker died after what his colleagues said was "a short illness."
Sources at the hospital on Tuesday told the Nation that at least 23 cases of the water-borne disease, eight involving staff, had been treated at the facility in April alone.
The hospital's cafeteria was closed indefinitely.
On March 22, Nairobi County health officials requested all referral hospitals within the city to reactivate their cholera treatment units following confirmation of the oubtreak in the city.
In a letter dated March 21, and addressed to all county medical superintendents, Nairobi County Director of Health Lucina Koyio said that all sub counties in Nairobi are on high alert.
"The county is experiencing a wave of cholera outbreak which was confirmed yesterday [Wednesday] March 20. In this regard, I am requesting all referral hospitals to reactivate their cholera treatment units to prevent the spread of the disease," said Dr Koyio.
"All sub-counties should be on high alert and treat all suspected cases of cholera as cholera cases. Please also reactivate your sub county response teams," said Dr Koyio.