Dengue Virus and Japanese Encephalitis Virus Epidemiological Shifts in Nepal: A Case of Opposing Trends

Abstract

Abstract. We report on the changing epidemiology of two important flaviviruses in Nepal: Japanese encephalitis (JE) and dengue viruses. Morbidity and mortality in Nepal is in the thousands since JE was introduced in 1978. Nepal launched an extensive laboratory-based JE surveillance in 2004. Nepal experienced a remarkable reduction in disease burden after mass immunizations from 2005 to 2010, when 2,040 JE infections and 205 JE-related deaths were confirmed. With its emergence in 2006, dengue has become a significant challenge in the country, highlighted by a sudden outbreak in 2010 that resulted in 359 confirmed dengue infections. Currently, both viruses cocirculate in Nepal. Here, we document the remarkable expansion of dengue in Nepal, which urgently requires national surveillance to refine the burden and make recommendations regarding control and prevention programs. We believe that the use of existing JE surveillance network for integrated dengue surveillance may represent the most appropriate alternative.Japanese encephalitis (JE) and dengue viruses are two important flaviviruses causing significant morbidity and mortality globally. Vaccine availability and widespread use coupled with vector control measures have significantly reduced JE burden in developed countries, 1 although persisting problems exist in developing countries with limited or no vaccine coverage. Unlike JE, dengue lacks licensed vaccines, making it a major public health problem; at least 2.5 billion people are at risk, and there are 100 million infections each year and considerable economic, political, and social costs worldwide. 2-4

Risk Factors for the Presence of Chikungunya and Dengue Vectors (Aedes aegypti and Aedes albopictus), Their Altitudinal Distribution and Climatic Determinants of Their Abundance in Central Nepal

“…Moreover, a simultaneous circulation of DENV and CHIKV has been reported in many recent studies [6,17]. These findings along with reports of DF cases from different districts of the Middle Mountain region, with the majority of cases from central Nepal [9,14], suggest that CHIKV and DENV have already expanded their distribution into higher altitudes of Nepal. Despite frequent outbreaks of DF, no previous record of CHIK cases can be attributed to a lack of differential diagnosis in Nepal [16].…”

Phylogenetic study reveals co-circulation of Asian II and Cosmopolitan genotypes of Dengue virus serotype 2 in Nepal during 2013

“…It was followed by a native report in 2006 with detection of four dengue serotypes (Malla et al, 2008). A few intermittent cases were reported nationwide from 2007 to 2009 with 2, 8 and 16 cases per year, respectively (Dumre et al, 2013;Griffiths et al, 2013). An outbreak occurred in 2010 with 350 (30%) confirmed cases out of 1215 clinically reported cases.…”

“…It is an endemic nation for many vector borne diseases, like malaria, kala-azar, Japanese encephalitis and lymphatic filariasis (Dumre et al, 2013). The first report of dengue fever came in 2004 from a Japanese traveler in Nepal and it was reported to be of serotype 2 (Takasaki et al, 2008) with >99% similarity with viral strains from India.…”

“…A large number of secondary infections are usually reported from the country and may be attributable to the circulation of multiple serotypes in the region (Malla et al, 2008;Dumre et al, 2013). There is lack of reliable dengue surveillance data from the country and inadequate response in accordance with international guidelines (Griffiths et al, 2013) that may hamper dengue control measures in the region.…”

Japanese encephalitis vaccines: Immunogenicity, protective efficacy, effectiveness, and impact on the burden of disease

“…More than several million cases of JE were reported from East Asia before the widespread use of vaccines; as much as 2% of the Chinese population has been reported to be affected between 1966 and 1971. 193 Vaccination for JE has been shown to decrease (a) the incidence of both JE and acute encephalitis syndrome (AES) in several countries or regions, including China,, 194,195 India,196 Japan, 197,198 Malaysia, 199 Nepal, 200,201 South Korea, 75 Sri Lanka, 202 Taiwan, 203204 and Thailand. 45 The introduction of JE vaccine reduced morbidity in China by 97% from 1971 to 2005.…”