Seroprevalence of Dengue in American Samoa, 2010

Abstract

Since the 1970s, regular dengue epidemics have caused considerable morbidity in the Pacific region. In 2009, an epidemic year, dengue incidence in American Samoa reached 644 cases per 100,000 population and decreased to 77/100,000 in 2010. However, human surveillance is limited and the true impact of dengue is unknown. A cross-sectional seroprevalence study was conducted from May to July 2010 with the primary aims of identifying risk factors for human leptospirosis, and providing an evidence base and tools to direct public health interventions in American Samoa. During the study, investigators encountered community concern about dengue and were asked by health authorities to utilize the collected serum for a dengue seroprevalence study. In October 2011, dengue serology was performed on blood samples from 794 participants aged 18-87 years at the Australian Army Malaria Institute (Brisbane, Australia). Samples were screened for the presence of dengue virus antibodies using PanBio Dengue IgG indirect enzyme-linked immunosorbent assay (ELISA) kits (Inverness Medical Innovations, Brisbane, Australia) following manufacturer recommendations and protocols. Overall 760 of 794 (95.6%) study participants tested positive for dengue IgG antibodies, demonstrating almost universal exposure of adults in American Samoa to dengue. This is the first population-based dengue seroprevalence study undertaken in American Samoa and the third highest dengue seropositivity rate reported in the world, behind Jamaica (100%) and the Dominican Republic (97.9%). Timely public health action is required to control dengue transmission, reduce dengue morbidity and minimize the risk of dengue haemorrhagic fever (DHF) and dengue shock syndrome (DSS) in American Samoa. Of foremost importance are the development of an active surveillance system, establishment of laboratory facilities for dengue serological testing, and implementation of a comprehensive prevention and control program.