Evolution of dengue in Sri Lanka—changes in the virus, vector, and climate (original) (raw)
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Severe Dengue Epidemics in Sri Lanka, 2003–2006
Emerging Infectious Diseases, 2009
Recent emergence of dengue hemorrhagic fever in the Indian subcontinent has been well documented in Sri Lanka. We compare recent (2003-2006) and past (1980-1997) dengue surveillance data for Sri Lanka. The 4 dengue virus (DENV) serotypes have been cocirculating in Sri Lanka for >30 years. Over this period, a new genotype of DENV-1 has replaced an old genotype. Moreover, new clades of DENV-3 genotype III viruses have replaced older clades. Emergence of new clades of DENV-3 in 1989 and 2000 coincided with abrupt increases in the number of reported dengue cases, implicating this serotype in severe epidemics. In 1980-1997, most reported dengue cases were in children. Recent epidemics have been characterized by many cases in children and adults. Changes in local transmission dynamics and genetic changes in DENV-3 are likely increasing emergence of severe dengue epidemics in Sri Lanka.
Emergence of Epidemic Dengue-1 Virus in the Southern Province of Sri Lanka
PLoS neglected tropical diseases, 2016
Dengue is a frequent cause of acute febrile illness with an expanding global distribution. Since the 1960s, dengue in Sri Lanka has been documented primarily along the heavily urbanized western coast with periodic shifting of serotypes. Outbreaks from 2005-2008 were attributed to a new clade of DENV-3 and more recently to a newly introduced genotype of DENV-1. In 2007, we conducted etiologic surveillance of acute febrile illness in the Southern Province and confirmed dengue in only 6.3% of febrile patients, with no cases of DENV-1 identified. To re-evaluate the importance of dengue as an etiology of acute febrile illness in this region, we renewed fever surveillance in the Southern Province to newly identify and characterize dengue. A cross-sectional surveillance study was conducted at the largest tertiary care hospital in the Southern Province from 2012-2013. A total of 976 patients hospitalized with acute undifferentiated fever were enrolled, with 64.3% male and 31.4% children. Co...
2015
Dengue, caused by the dengue virus (DENV) is the most important vector borne infection in the tropics and can present as dengue fever(DF) or dengue haemorrhagic fever(DHF). 1 DENV exists as four different serotypes, all of which have been circulating in Sri Lanka for the past 30 years. 2 DENVs are transmitted by the mosquito species Aedes aegyptii and Aedes albopictus, both of which are endemic to the South Asian region of the world. In Sri Lanka, the primary vector in transmitting DENV is A. aegyptii while A. albopictus serves as the secondary vector. 3
Severe Dengue Epidemic, Sri Lanka, 2017
Emerging Infectious Diseases
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
Parasites & Vectors, 2021
Background Spatial and temporal changes in the dengue incidence are associated with multiple factors, such as climate, immunity among a population against dengue viruses (DENV), circulating DENV serotypes and vertical transmission (VT) of DENV in an area at a given time. The level of VT in a specific location has epidemiological implications in terms of viral maintenance in vectors. Identification of the circulating DENV serotypes in both patients and Aedes mosquito larvae in an area may be useful for the early detection of outbreaks. We report here the results of a prospective descriptive study that was conducted to detect the levels of VT in Aedes mosquito larvae and circulating DENV serotypes in patients and Aedes mosquito larvae from December 2015 to March 2017 in an area of Sri Lanka at high risk for dengue. Methods A total of 200 patients with clinically suspected dengue who had been admitted to a tertiary care hospital during a dengue outbreak (3 study periods: December 2015–...
PLOS Global Public Health
With the onset of the COVID-19 pandemic in early 2020 there was a drastic reduction in the number of dengue cases in Sri Lanka, with an increase towards the end of 2021. We sought to study the contribution of virological factors, human mobility, school closure and mosquito factors in affecting these changes in dengue transmission in Sri Lanka during this time. To understand the reasons for the differences in the dengue case numbers in 2020 to 2021 compared to previous years, we determined the association between the case numbers in Colombo (which has continuously reported the highest number of cases) with school closures, stringency index, changes in dengue virus (DENV) serotypes and vector densities. There was a 79.4% drop in dengue cases from 2019 to 2020 in Colombo. A significant negative correlation was seen with the number of cases and school closures (Spearman’s r = -0.4732, p <0.0001) and a negative correlation, which was not significant, between the stringency index and c...
Parasites & Vectors, 2021
Background The larval bionomics of Aedes across the Jaffna peninsula in northern Sri Lanka was investigated to obtain information needed for developing more effective larval source reduction measures to control endemic arboviral diseases. Methods The habitats of preimaginal stages of Aedes mosquitoes were surveyed, and ovitrap collections were carried out in densely populated areas of the Jaffna peninsula. Aedes larval productivities were analysed against habitat characteristics, rainfall and dengue incidence. Adults emerging from collected larvae were tested for dengue virus (DENV). Results Only Aedes aegypti, Ae. albopictus and Ae. vittatus were identified in the field habitat collections and ovitraps. Aedes aegypti was the predominant species in both the field habitat and ovitrap collections, followed by Ae. albopictus and small numbers of Ae. vittatus. Tires and open drains were the preferred field habitats for Ae. aegypti, although larval productivity was higher in discarded pl...
Synopsis of findings from recent studies on dengue in Sri Lanka
Dengue …, 2006
The pattern of dengue in Sri Lanka changed after 1989, with an exponential increase in the incidence of DHF. In 2004, a major epidemic of dengue infection occurred in Sri Lanka, which accounted for 15 457 cases and 88 deaths. The findings from recent studies on dengue are outlined here, which highlight the implications with regard to the management and control of this infection in the country.
Tropical Medicine and Health, 2011
Unprecedented incidences of dengue have been reported in Sri Lanka in recent years. The district of Batticaloa, which was devastated by the 2004 Asian tsunami, is one of the districts affected by dengue. One option to curtail this disease is to implement appropriate vector control measures. A nine-month study was carried out within the Batticaloa Municipal Council limit from April to December 2008. Larval collections were conducted fortnightly using conventional ovitraps for nine months covering the dry and wet seasons. Ovitraps (indoor and outdoor) were placed in 15 randomly selected houses. The collected larvae were brought to the laboratory and reared under laboratory conditions. The larval forms and emerged adults were identified on the basis of reported morphological descriptions. The identified adults of 2-3 d old were exposed to common insecticides following the WHO protocol. During the study period, a total of 10,685 Aedes aegypti and Ae. albopictus mosquitoes were collected, with the former constituting 57% of the total sample. Both species were collected from indoor and outdoor ovitraps, and their prevalence was recorded throughout the study period. A seasonal shift was observed in the density, with Ae. aegypti predominating during the dry season and Ae. albopictus during the wet season. Both species were highly resistant to 4% DDT and susceptible to 0.25% permethrin. The continuous presence of potential dengue vectors may have contributed to the dengue prevalence in the district. Since both species can oviposit in indoor and outdoor ovitraps, public awareness and participation should be promoted in the vector control programme of the Ministry of Health along with continuous vector surveillance.