Background and aim:  Malaria as a mosquito-borne disease is largely dependent on climatic conditions. Temperature, rainfall and relative humidity are considered as climatic factors affecting the geographical distribution of this disease. These climatic factors have definite roles not only in the growth and proliferation of the mosquito Anopheles but also in the parasite Plasmodium activity. The purpose of this study was to find in which regions of Iran climatic conditions favour spread of malaria.

Material and Methods: Data on 3 climatic factors, including the mean monthly temperature, rainfall and mixed ratio of humidity, obtained from 31 synoptic meteorological stations during the 30-year period 1975-2005 were used. By running the informative filters through map algebra tools in the Geographical Information System (GIS), the synoptic meteorological stations were classified into 4 groups in terms of climatic conditions favouring activity and proliferation of the mosquito Anopheles and the parasite Plasmodium. Then the regions were interpolated in terms of climate risk of malaria incidence using the tension Spiline interpolation method.

Results: The maps of climatic potential malaria risk indicated that the southern provinces including Hormozgan, Bushehr and Khuzestan, southern parts of Sistan-Balouchistan province, such as Chabahar and Nikshahr, as well as Northern provinces of the country, including Mazandaran and Gilan, have the highest climatic potential for risk of malaria spread. On the other hand, provinces in the North Western region, including West and East Azarbaijan, Ardebil, Kurdistan and Zanjan, have the lowest climatic potential risk of malaria spread. Further analysis of the data showed that a large segment of the population is living in regions with medium- to high-risk zones.

Conclusion: The findings of this study can be used when designing malaria control programs to identify different regions in terms of climate-based malaria risk. The presented risk map of malaria in this study is completely based on climatic factors. The disconformity between these presented climate-based maps and the observed high-risk map is due to such factors as socioeconomic and lifestyle changes, as well as border problems (foreign subjects entering the country).