Background Dengue infection, which causes dengue fever, dengue haemorrhagic fever and dengue shock syndrome are currently endemic or intermittently epidemic in many tropical and sub-tropical regions of the world. According to the WHO, dengue has recently become a major public health concern globally. It is generally found in tropical and sub-tropical regions, and more specifically in urban and semi-urban areas.

Objective To study the relationship of dengue fever and climate factors.

Methods The confirmed dengue infections in hospital cases were detected through the hospital information system. Monthly data for total rainfall, temperature and relative humidity for the year 2010 were obtained from Meteorological Department of Karachi.

Results Overall, 576 cases were positive for dengue and hospitalised during 2010. The mean age was 30±17.66 years and 391 (67.9%) were males. Out of 576 cases, 476 (82.6%) were adults. Dengue infection cases were reported during warmest weather with maximum number of cases 226 (39.2%) reported in the month of October 2010 followed by 135 (23.4%) in the month of September 2010. The difference between number of positive cases during different months was significant (p=0.03).

Conclusion These results suggest that climate factors such as temperature and rainfall may be responsible for an outbreak of dengue infection. Dengue viruses have a known transmission cycle, but changes in temperature or rainfall may have varied local effects.