Possible Drivers of the 2019 Dengue Outbreak in Bangladesh: The Need for a Robust Community-Level Surveillance System

Abstract

Bangladesh experienced its largest dengue virus (DENV) outbreak in 2019, with 101,354 patients admitted to hospital with either laboratory-confirmed or clinical diagnosis. By contrast, the cumulative number of dengue patients admitted to hospitals in the previous 19 yr (2000–2018) was 50,674 (Institute of Epidemiology Disease Control and Research 2019). Herein, we discuss the potential drivers contributing to the unprecedented 2019 DENV outbreak in Bangladesh.

Dengue fever is caused by four serotypically distinct dengue viruses (DENV-1 to DENV-4) that are transmitted by Aedes spp mosquitoes. Infection with one serotype does not protect against another, except for the first few months after infection (Sabin 1952). Since 2000, Bangladesh has reported DENV cases every year before the 2019 surge (Fig. 1). However, under-reporting was highly likely because previous reports only included data from a select number of government hospitals and private clinics (Directorate General of Health Services [DGHS] 2019, Mamun et al. 2019). The number of dengue patients reported by the Institutes of Epidemiology Disease Control and Research (IEDCR), a research wing of the Ministry of Health and Family Welfare, includes patients from in-patient departments of 12 government or autonomous hospitals and 29 of 609 private hospitals (Bangladesh Private Clinic Diagnostics Owners Association: http://www.bpcdoa.com/about_us.html). Dengue cases were identified based on clinical symptoms (including fever and rash) and/or laboratory tests for IgM or IgG antibodies to DENV, and nonstructural 1 protein (NS-1) of DENV (Diseases Control Division (DGHS) 2013). Nevertheless, data on asymptomatic infections or patients that developed mild symptoms and did not seek medical attention were unknown and were not included in these data.