Dengue seroprevalence in Golfito and the central district of Puntarenas, Costa Rica 2005-2006

Abstract

Justification and objectives: Dengue infection could be asymptomatic or it can produce a mild acute febrile illness, dengue fever, or a severe illness, such as hemorrhagic dengue or shock syndrome (DHF/SSD). Illness severity depends upon various risk factors like viral characteristics, infestation of the vector as well as host factors; presence of more than 1 dengue virus serotype and secondary infections. Since 1993 when the first cases of dengue were reported in Costa Rica Puntarenas's First District population has been 1 of the most affected areas, although there has been a decline in the incidence over the last years. The Brunca Region was the second with high incidence of dengue in 1998 and since then cases have been reported permanently. The national incidence is based on the clinical cases weekly report by the Ministry of Health, but there are no seroepidemyological studies to determine the seroprevalence of the disease. Determining IgG antibodies prevalence against dengue at the First Puntarenas's District and at Golfito district will allow us to better understand the incidence and calculate the percentage of the population at risk of developing DHF/SSD associated with the epidemiological data.
Methods: For the seroprevalence study we collected 210 sera samples from each region and used an IgG capture ELISA developed and standardized in our laboratory using as reference the Dulbecco Plaque Method. Samples were obtained utilizing the EPI method (Expanded Program on Immunization) described by the World health Organization (WHO).
Results: The study showed 43.8% (92) and 90% (189) prevalence in the districts of Golfito and Puntarenas respectively, no significant differences in gender, age and geographical location were found. We determined an 83% in Golfito and a 95% in Puntarenas correlation between serology and symptomatic cases and 42% from total seropositive people in each region denied having clinical symptoms. Since this is a representative sample study we can affirm that a similar percentage of asymptomatic cases occur in the general population.
Conclusions: Seropositivity against dengue virus in the First Puntarenas's District population is very high (90%) and although the Golfito District has been reported with a low prevalence since 1998, this study shows that near 50% of the population is seropositive with the consequent risk for DHF/SSD. It is very important to continue this type of seroepidemiological studies in other regions of the country to verify the real threat of this disease in order to take the necessary preventive measures.