Background: In 1981, Cuba reported a DHF epidemic by Den 2. The epidemic was preceded by a Den 1 DF outbreak. Later on, several epidemics (1997, Den 2, 2001 Den 3, 2006 Den 4/Den 3) and one small outbreak (2008, Den 2) with DHF cases were observed, all of them totally eliminated. Trying to understand dengue pathogenesis and taking into account the epidemiological situation, several sero-epidemiological surveys were performed. Objectives: To estimate the rates of symptomatic (DF/DHF) and asymptomatic infections taking into account the epidemiological situation of the country. Material and method: To estimate the rates of symptomatic (DF/DHF) and asymptomatic infections taking into account the epidemiological situation of the country. Three sero-epidemiological surveys were developed after the epidemics of 1981, 1997 and 2001 in three densely populated municipalities (Cerro, Santiago de Cuba and Playa). Samples were tested by PRNT to dengue viruses. Clinical, sero-epidemiological, genetic & immunity studies were developed to determined risk factors for DHF/DSS and for clinical over. Here some epidemiological data are reported. Conclusion: Secondary infection including the 2d infecting virus and the sequence of infection are risk factors for DHF but also influence in dengue disease outcome of infection. Most Den 2 primary infections were silent while secondary Den1/Den 2 followed by Den 1/Den 3 were associated to a higher severity and clinical over. Most tertiary infections were silent or mild. Other studies reported in Cuba and not included here (host genetic & immunity & the viral characteristics support the multifactorial hyphotesis of DHF/DSS