The relationship between vector-borne diseases and climate conditions has been analyzed in many reports and is based on the underlying life conditions of the vectors in different climates. As the seasons for reproduction of vectors (for instance mosquitoes) lengthen the risk of diseases like malaria and dengue fever may increase in the local populations. The risks can be quantified from estimates of the annual length of breeding season, or the seasonal variation of rainfall, which creates breeding sites for the vectors. Other risk related variables is, of course, the local access to bed-nets or other vector protection methods. Another factor of importance is the daily activities of the local populations. If their agricultural work involves wading around in water diseases such as schistosomiasis can be a climate related risk, as it is in parts of China. If agricultural work is difficult to carry out in the middle of the day, due to local heat conditions, and more work is carried out during dawn and dusk, when mosquitoes are the most active, it may increase risk of malaria.
Some vector-borne diseases, such as malaria, are also a recurrent problem, which can affect the same victim numerous times in a similar manner to chronic conditions.