Excess Mortality Related to Chikungunya Epidemics in the Context of Co-circulation of Other Arboviruses in Brazil

Introduction Chikungunya is an emerging arbovirus that reached the Western Hemisphere at the end of 2013. Studies in the Indian Ocean and India suggest that passive surveillance systems cannot recognize many of deaths associated with chikungunya, which can be inferred by an increase in the overall mortality observed during chikungunya epidemics. Objective We assess the mortality associated with chikungunya epidemics in the most affected states in Brazil, from 2015 and 2016. Methods We studied the monthly mortality by age group, comparing a period without epidemics to a chikungunya epidemic period, which we defined arbitrarily as consecutive months with incidences of more than 50 cases/100,000 persons. Results We obtained official data from the National System of Reported Diseases (SINAN) and the Mortality Information System (SIM), both maintained by the Ministry of Health. We identified a significant increase in the all-cause mortality rate during chikungunya epidemics, while there was no similar mortality in the previous years, even during dengue epidemics. We estimated an excess of 4,505 deaths in Pernambuco during the chikungunya epidemics (47.9 per 100,000 persons).The most affected age groups were the elderly and those under 1 year of age, and the same pattern occurred in all the states. Discussion Further studies at other sites are needed to confirm the association between increased mortality and chikungunya epidemics indifferent age groups. If these findings are confirmed, it will be necessary to revise the guidelines to recognize the actual mortality associated with chikungunya and to improve therapeutic approaches and protective measures in the most vulnerable groups.