Frequency and tendency of malaria in Colombia, 1990 to 2011: a descriptive study

BACKGROUND: Malaria is a serious health problem in Colombia. This paper intends to analyse the frequency and tendencies of the disease in Colombia over the last 22 years. The researchers used the Box-Jenkins (ARIMA) methodology for the analysis of time series. METHODS: This descriptive study was done retrospectively by using the morbidity records of the Ministry of Health and of the System for the Monitoring of Public Health (SIVIGILA). The information about the population was obtained from the National Administrative Department of Statistics (DANE). The incidence rate according to age and sex was calculated from 1990 to 2011. Also, the Annual Parasite Index (API) for Plasmodium falciparum and for Plasmodium vivax was calculated. The mortality rates per year, from 1990 to 2011, were determined. Finally, the Box-Jenkins (ARIMA) methodology was used for the analysis of time series, grouped weekly. Information for ARIMA modelling was used from the year 2001. RESULTS: The total number of reported cases from 1990 to 2011 was 2,964,818 cases with an annual average of 134,764. In the period from 2001 to 2005 and from 2006 to 2011 a significant decrease of annual cases was observed. In general, a predominance of P. vivax over P. falciparum was observed. With respect to the API, it must be noted that there were peaks in 1994 in the departments of Guainía and Guaviare, and in 1998 in Guaviare and Chocó. The department of Antioquia showed a tendency towards a decrease of the API through the years. In the time series model there were no statistically significant seasonal patterns for the total number of cases of malaria. However, for P. falciparum the number of cases was statistically significant. Lastly, between 1990 and 2009, there were 1,905 deaths caused by malaria in Colombia with a significant tendency towards a decrease in deaths over those years. Plasmodium falciparum was more lethal than P. vivax. CONCLUSIONS: In Colombia, the transmission of malaria occurs in an endemic and epidemic context, which keeps an unstable endemic transmission pattern. Several factors specific to a country such as Colombia encourage the dissemination and permanence of the illness.