Twenty-six new cases of the viral Chikungunya fever have been reported in the county.
The cases were diagnosed at the Kenya Medical Research Institute (Kemri), bringing to 58 the number of recorded and confirmed cases in the coastal city.
On Tuesday Governor Hassan Joho (above) led a team of officials in a fumigation and spraying campaign of mosquito breeding areas.
The fever has spread rapidly, threatening tourism.
A report by the health services chief officer, Khadija Shikely, and issued on Thursday by the county government spokesman, Richard Chacha, said that of the 37 samples taken to Kemri this week, 26 were positive.