The pandemic coincides with the long rainy season in Kenya. Rain increases mosquito breeding sites, vector density and thus transmission of mosquito-borne diseases.
Prolonged rains increase the amount of stagnant water in the environment in which mosquitoes breed. This increases the risk of mosquito-borne diseases.
There's a big market for new treatments for TB, malaria and other ailments. But most of these diseases afflict low-income people unable to pay for medicine.
The more water, the more mosquito eggs are laid, and the more mosquitoes end up buzzing about. But to spread disease to people, they first need to bite infected wildlife.