Chikungunya Fever: A Killer Epidemic in Ahmedabad City, India

Background The Chikungunya virus is an alphavirus native to tropical Africa and Asia and is transmitted to humans by the bite of infected Aedes mosquitoes. The symptoms of Chikungunya include sudden onset of fever, severe arthralgia, and maculopapular rash. Thirty percent of the population on the French Réunion Island was afflicted with Chikungunya in the past year. They reported 237 deaths. India on the other hand reported 1.39 million cases of Chikungunya but no deaths. Methods Mortality data from 2002-2006 was obtained from the Ahmedabad Municipal Corporation (AMC). Actual mortality rate of 2006 was compared to the mortality rate of 2002-05 and its statistical significance tests were carried out. Findings Mortality data obtained from the Ahmedabad Municipal Corporation (AMC) suggests that 3112 excess deaths occurred in August-November (epidemic period) compared to the average deaths in the same months during the previous four years. These differences in deaths were found to be highly statistically significant. A peak in excess mortality is seen in the month of September when 1489 additional deaths were recorded. Case fatality rates for Ahmedabad also turn out to be much higher than that of the Reunion Island. Interpretation The Chikungunya epidemic was raging when the excess deaths occurred. There were no other adverse events or other epidemics that took place could explain this excess mortality. Government authorities, WHO and other international public health agencies should take these findings of excess mortality seriously and investigate into this occurrence of excess deaths to understand this reemerging disease and prevent future epidemics and mortality.