The other counties with a high prevalence rate are Siaya (21 percent), Homabay (20.7 percent), Kisumu (16.3 percent), Migori (13.3 percent) and Busia (7.7 percent).
Nairobi County is among the top ten counties in the country that has a high HIV prevalence.
In new findings released this week by the National Aids Control Council (NACC), Nairobi County had a prevalence of 6.1 percent which is higher than the National Prevalence which is 4.9 percent.
NACC, however, said that the number of people living with the virus in the country had dropped in the past eight years.
It also said that cases had also dropped across all ages with prevalence among adults aged between 15-49 dropping from 0.35 in 2010 to 0.19 last year.
Nationally, the number of those affected dropped from 77,200 to 52,800 in the last eight years.
The top 10 counties with the highest prevalence rate, according to NACC, are Siaya (21 percent), Homabay (20.7 percent), Kisumu (16.3 percent), Migori (13.3 percent) and Busia (7.7 percent).
Others were Nairobi (6.1 percent), Kisii (4.4 percent), Trans Nzoia (4.3 percent) with Murang'a and Nyamira tied at 4.2 percent.