[Estimation of underreporting of Chikungunya virus infection cases in Girardot, Colombia, from November, 2014, to May, 2015].

INTRODUCTION: Chikungunya virus infection in Colombia became epidemic in 2015. It is estimated that there is underreporting of cases to the public health surveillance system which can induce bias in epidemiological projections for decision making, a serious problem, as it veils the real magnitude and actual epidemiological importance of this disease.

OBJECTIVE: To estimate the underreporting of cases of chikungunya infection in the municipality of Girardot, Cundinamarca, from November, 2014, to May, 2015.

MATERIALS AND METHODS: We conducted a descriptive and retrospective study using surveys in 132 blocks selected by simple random sampling for community active search and the revision of 100% of the individual records of health services and those from the public health surveillance system for institutional active search. The data were analyzed using EpiInfo, version 7.

RESULTS: The attack rate was 64.7%. The estimated underreporting was 36.1% for not attending medical consultation while 24.9% of cases were not reported to the public health surveillance system. The principal cause for not seeking medical consultation among those surveyed (n=392; 43%) was self-medication, followed by the collapse of health services (n=207; 23%).

RESULTS: The attack rate was 64.7%. The estimated underreporting was 36.1% for not attending medical consultation while 24.9% of cases were not reported to the public health surveillance system. The principal cause for not seeking medical consultation among those surveyed (n=392; 43%) was self-medication, followed by the collapse of health services (n=207; 23%).

CONCLUSION: The overall underreporting since the beginning of the epidemic in Girardot was 87.05%.This research explains 60.9% of this underreporting.