Severe Dengue Epidemic, Sri Lanka, 2017

Abstract

G lobal incidence of dengue has increased 7-fold, from 8.3 million cases in 1990 to >58.4 million in 2013 (1). Currently, ≈390 million new infections occur annually in 128 dengue-endemic countries (2). Worldwide, ≈14,000-20,000 dengue-related deaths occur each year (1,2). In dengue-endemic countries, Aedes (Stegomyia) aegypti and Ae. (Stegomyia) albopictus mosquito vectors transmit the disease. Sri Lanka, a tropical island in the Indian Ocean (population 21 million) (3), has reported dengue cases since the 1960s; seasonal epidemics predominantly affect areas that have annual rainfall >2,500 mm (4). However, until 1988, the more severe form of dengue virus (DENV) infection, dengue hemorrhagic fever, was reported only sporadically (5,6). During 1991-2008, dengue epidemics occurred once every few years on the background of endemic transmission (6). A disproportionate epidemic occurred in 2009 comprising 35,008 suspected cases (incidence 170 cases/100,000 population) and 346 deaths (case-fatality rate 1%) (7). During 2010-2016, dengue became a major public health problem; cases increased steadily (from 28,473 in 2011 to 55,150 in 2016) throughout the country but disproportionately affected the most populated Western province (7). In 2017, a total of 186,101 suspected cases and 440 dengue-related deaths were reported to the Central Epidemiology Unit of the Ministry of Health, Sri Lanka (7). This number is the highest number of suspected cases reported in a single calendar year in Sri Lanka since dengue was designated a notifiable disease in 1996. We compared the temporal, epidemiologic, virologic, entomologic, and climatic characteristics of the 2017 dengue epidemic with those of the epidemics during the preceding 5 years (2012-2016). Methods Data Sources Epidemiology We obtained epidemiologic data from the integrated national communicable disease surveillance system, which captures symptomatic dengue patients classified according to a standard case definition based on the 1997-2011 World Health Organization classification (8). Etiologic screening was conducted with NS1 antigen testing or dengue antibody assays. However, given the limited diagnostic test availability, especially in remote areas of the country, many cases were clinically diagnosed using the surveillance case

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“…From 2010 to 2016, dengue became a major public health problem, with a steady increase in cases from 28,473 to 55,150 cases in 2011 and 2016 respectively [ 10 ]. In 2017, Sri Lanka reported 186,101 dengue cases and 440 deaths (case fatality rate 0.24%), the highest number of cases reported in one year since dengue was incorporated into the integrated disease surveillance system as a notifiable disease in 1996 [ 11 ]. In 2019, a total of 104,695 cases with 157 deaths (case fatality rate 0.15%) were reported [ 12 ].…”

Changing epidemiology of dengue in Sri Lanka—Challenges for the future

“…DENV-2 and DENV-3 were not detected from the year 2009 to mid-2016, although the predominant circulating serotypes prior to the year 2009 were DENV-2 and DENV-3 [ 10 – 12 ]. The largest reported epidemic of dengue was seen in 2017, with a total number of 186,101 cases being notified with 440 deaths, which coincided with the reemergence of DENV-2 [ 13 ]. Although fewer cases were reported in 2018 (51,659 cases) compared to 2017, there was again another surge in 2019, with 105,049 cases reported [ 14 ].…”

Emergence of Genotype I of Dengue Virus Serotype 3 during a Severe Dengue Epidemic in Sri Lanka in 2017

“…In 2017, an unprecedented magnitude of severe dengue epidemic occurred in Sri Lanka and cosmopolitan genotype of DENV-2 was dominant in the most affected district (19). In our previous study on this outbreak 14, we reported the detection of cosmopolitan genotype of DENV-2 (74%) and genotype I of DENV-4 (1%).…”