Changing Epidemiology of Dengue Fever: Newer Insights and Current Concepts

Background: Dengue fever (DF) is the most common of the arboviral infections in humans and more than two-fifths of the world's population lives in areas potentially at risk for dengue. Effective vector control, prompt case detection and appropriate clinical management can reduce the mortality from severe dengue. The objective of this paper is to present current epidemiology of dengue in this part of the country and, additionally, reflect on some important clinical issues involved in the management of these cases. The global incidence of DF and dengue hemorrhagic fever (DHF) has increased dramatically in recent decades. Endothelium is the target of the immune-pathological mechanism in DF and DHF, its hallmark being vascular permeability and coagulation disorders. Plasma leakage or capillary leak syndrome (CLS) is the most specific and life-threatening feature of DHF and is considered to be the primary lesion that underlies DHF.

Materials and Methods: The present study is a four year (January 2013- December 2016), retrospective observational study. The study population consists of 264 male or female indoor patients with confirmed diagnosis of dengue fever. Inclusion criteria were discharge diagnosis with International Classification of Disease (ICD) code A90 - A91 and availability of minimal dataset (name, registration number, age, sex, diagnosis, symptoms, laboratory investigations, transfusions if any, co-infection, other co-morbidities, date of admission, date of discharge, and discharge status). Indoor files of all these 264 cases were collected from medical records department and data tabulated. The study focuses on incidence and outcomes of CLS in dengue infection along with other various issues among these patients.

Results: In all 264 patients were included in the study with a male female ratio of 1.6:1. The youngest and the eldest patient were of 13 year and 95 year age respectively. Primary dengue fever (pDF) was seen in 219 (83%) and secondary dengue fever (sDF) in 45 (17%) cases respectively. Besides fever, chills, vomiting, abdominal pain, body-ache, bleeding manifestations, and hepato-splenomegaly, features of CLS were present in 164 (62.1%) cases. None of the cases had only left side pleural or pericardial effusion. In all 258 (97.7%) cases had thrombocytopenia, 39 (14.8%) cases had bleeding manidestations, 11 (4%) cases had severe organ involvement, 19 (7.2%) cases had co-infections, 43 (16.3%) cases required medical intensive care unit (MICU) admissions, and there were only 4 (1.5%) mortalities. The pathophysiology and management challenges of CLS along with other parameters are discussed.

Conclusion: Currently, no specific antiviral therapy exists for dengue virus. With prompt case detection and appropriate clinical management, the case fatality rate (CFR) is declining and the overall CFR in the southeast Asia region is now less than 1%. In our case series it was 1.5%. We conclude that patients of DF with thrombocytopenia and transaminitis should be evaluated early by ultrasonography for CLS. Hemoconcentration and hypoproteinemia are not sensitive tools to pick up capillary leakage in clinical practice. Isolated left side pleural effusion and pericardial effusion are not seen in DF and if present one should look for another cause. The case series raises question on the accepted theory of relation between capillary leakage and severe dengue infection. Further, since capillary leakage was seen in 78.8% of primary dengue infection cases, it also questions the validity of the immune enhancement theory of DHF/severe dengue. Viral burden may be a key factor in determination of disease severity rather than sequential infections or secondary infection. Early detection and appropriate case management practices are critical factors for survival.