A Study on Incidence and Serotyping of Dengue in a Tertiary Care Hospital.

INTRODUCTION : We stand on the brink of an era in which millions of people are likely to be safer from some of the most terrifying and maiming diseases. But, some new and previously unknown diseases continue to emerge, which are often labelled as ‘re-emerging diseases’. These, amount to a crisis that is a challenge for the public health system in many parts of the world. Viral haemorrhagic fevers are becoming increasingly common in the tropics and subtropics. Dengue fever is currently the most important arthropod borne viral disease because of its widespread distribution in more than 100 countries and its potential for extensive outbreaks of life-threatening disease. Two-fifths of world’s population or 2500 million people are now at risk for dengue and every year approximately 50 million new cases occur worldwide. Dengue virus was first isolated in India in the year 1945 and is endemic in both urban and semi-urban areas. Dengue fever has struck again in India and cases of dengue fever (DF)/dengue haemorrhagic fever (DHF) have been reported from various parts of the country During the last 4 decades. During the epidemics of dengue, attack rates among susceptibles are 40-90% and an estimated 5,00,000 cases of DHF require hospitalization each year, of whom a very large Proportion are children. Dengue virus, belonging to the genus Flavivirus and Family Flaviviridae, are mosquito borne viruses and the principal vector, Aedes aegypti is a day-biting mosquito of public importance that breeds in natural or artificial waters. Since the occurrence of dengue infections and complications like DHF and DSS are Increasing, this study was conducted to study the incidence of Dengue infections, to evaluate the seropositivity and to determine the serotype of dengue Virus in a tertiary care setup, thereby to create awareness about the preventive measures to be taken by the general public and the health care system, and to improve our infrastructure for diagnosing and treating dengue infections. AIMS OF THE STUDY : To study the incidence of dengue cases among patients with fever in a tertiary care hospital. To determine the seropositivity of Dengue cases. To categorise dengue cases as dengue fever, dengue haemorrhagic fever and dengue shock syndrome, according to WHO guidelines. To evaluate the proportion of primary and secondary dengue infections. To determine the serotype of dengue virus in dengue positive cases in the early febrile period. MATERIALS AND METHODS : Blood samples from 250 patients with clinical features suggestive of dengue, were included in this study. The samples were collected aseptically and serum was separated by centrifugation technique and stored at -70˚C. Inclusion Criteria : The clinical basis for diagnosing the patients as having dengue fever was based on standard criteria like presentation of febrile illness of 2-7 days duration, with features like headache, myalgia, arthralgia, rash, haemorrhagic manifestations and leucopenia. Exclusion Criteria: Patients with clinical evidence of urinary tract infection, pneumonia, abscess or any other apparent cause of fever were excluded. The proportional data of this cross-sectional study was tested using Pearson’s Chi-Square ( X2 )analysis test, Two sample binomial proportion test, Statistical analyses were carried out using Statistical Package for Social Sciences( SPSS) and Epi-Info softwares. The samples were subjected to PANBIO Rapid Duo Cassette method, IgMELISA & IgG ELISA at Institute of Microbiology, Madras Medical College & General Hospital, Chennai. Single-step nested RT- PCR was done for 28 samples at Christian Medical College, Vellore. CONCLUSION : • The incidence of dengue was 0.88% among patients attending the fever clinic and patients admitted with fever in Government General Hospital, Chennai. The seropositivity of dengue cases was 36%. • The dengue cases were classified according to WHO guidelines and were found to be 50% of Dengue fever cases, 42.22% of Dengue haemorrhagic fever cases and 7.7% of Dengue shock syndrome cases. The proportion of primary dengue infections (28.88%) to secondary infections (71.11%) was 1:2.5. The serotype of dengue virus isolated in the present study belonged to Dengue virus serotype-1. Serum samples should be collected at a very early period (1-3 days) within onset of fever to determine the dengue serotype by Single-Step Nested RT- PCR. Serological diagnosis should be done in all clinically suspected dengue cases for early initiation of treatment and thereby to minimize the mortality