Epidemic outbreak of Chikungunya in two neighboring towns in the Colombian Caribbean: a survival analysis.

BACKGROUND: The first autochthonous Chikungunya virus transmission in Colombia was reported in September 2014. Three months later, every town in the Caribbean region was affected, including the bordering towns of Ovejas and Corozal, in the department of Sucre. The objective of the study was to analyze and compare the temporal dynamics of the outbreak of Chikungunya in two towns of the department of Sucre.

METHODS: Households with suspicious cases with clinical symptomatology for Chikungunya were enrolled. In each house an epidemiological questionnaire was applied to collect economic and social information and methods for vector control.

RESULTS: The study analyzed data collected between 09/01/2014 and 01/31/2015; 458 families in Corozal and 516 families in Ovejas were identified with Chikungunya cases. Estimated attack rates were 10,621 cases and 1640 cases per 100,000 inhabitants, in Ovejas and Corozal, respectively. The 75-day survival curve was 27.2% lower (0.632, CI = 0.614-0.651) in Ovejas than in Corozal (0.904, CI = 0.891-0.917). After 120 days, both curves showed a stable horizontal slope, close to a survival probability of 0.54, indicating the end of the epidemic period. The log-rank test (X(2) = 94.6, 1fd, p-value = 0.000) showed the improved survival of Chikungunya in the town of Corozal. The relative risk between the two towns was 0.863 (CI = 0.809-0.921; p-value < 0.001).

CONCLUSIONS: The dynamics of the temporal distribution of CHIKV could be influenced by socioeconomic and preventable risk factors. Poor socioeconomic conditions such as the lack and poor efficiency of water supply and waste collection services could be determining factors in the proliferation of CHIKV. The survival analysis proved to be a suitable method for studying the presentation of CHIKV and can be applied to other prevalent vector-borne diseases such as the ZIKA and Dengue.