I understand your point, but still, in a country of 50+ million people in Kenya, there's 1.6 or so living with HIV. Would these cases not just be in the more rural and semi-rural areas rather than cities like Mombasa and Nairobi?
I don't know the specifics of Kenya, but typically you would expect more STDs in inner cities where you have a lot of people on minimal wages living in close proximity, with higher incidences of prostitution, drug taking, homosexuality and promiscuity. All are less likely in village areas.
In Africa as a whole, HIV is generally assumed to follow the trucking routes between cities. For instance the Mombasa-Kampala highway has a reputation as an HIV route
I know its wiki, but its worth reading
External Link/Members Onlytwo points stand out:
Sex workers are the most affected group within the country. Research has shown that around 30% of sex workers are HIV positive.
A study of Nairobi sex workers in 2015 reported about two thirds always use condoms with clients. This compares with 40% amongst members of the general public who have two or more partners