Abstract
INTRODUCTION: Dengue virus (DENV) causes a wide range of diseases in humans, from acute febrile
illness Dengue fever (DF) to life-threatening Dengue hemorrhagic fever (DHF) or Dengue
shock syndrome (DSS). Factors believed to be responsible for spread of Dengue virus
infection include explosive population growth, unplanned urban overpopulation with
inadequate public health systems, poor standing water and vector control, climate
changes and increased international recreational, business, military travel to endemic
areas. All of these factors must be addressed to control the spread of Dengue and
other mosquito-borne infections. The detection of Dengue virus RNA by reverse transcriptase
PCR (RT-PCR) in human serum or plasma samples is highly indicative of acute Dengue
fever. Moreover, the method is able to identify the Dengue virus serotype by demonstrating
defined sequence homologies in the viral genomic RNA.
METHODS AND RESULTS: During the nine year period of this study analysis, 6767 strongly suspected cases
were tested by RT-PCR. 1685 (24.9%) were Dengue PCR positive and confirmed as Dengue
cases. Observations on the seasonality were based on the nine year's data as the intensity
of sampling was at its maximum during monsoon season. Dengue typing was done on 100
positive samples after storage of Dengue RNA at – 80°C. Dengue serotypes were detected
in 69 samples of which Dengue 2 was most predominant. 576 samples were processed for
NS1 antigen and PCR simultaneously. 19/576 were positive (3.3 %) for NS1 as well as
by PCR. 23/576 samples were negative for NS1 antigen, but were positive by RT-PCR.
The remaining 534 samples which were negative for NS1 antigen were also negative by
Dengue RT-PCR.
CONCLUSION: In this study we sought to standardize rapid, sensitive, and specific fluorogenic
probe-based RT-PCR assay to screen and serotype a representative range of Dengue viruses
that are found in and around Mumbai. Qualitative Dengue virus TaqMan assays could
have tremendous utility for the epidemiological investigation of Dengue illness and
especially for the study of the viremic response with candidate live-attenuated dengue
virus vaccines.
Key words
Dengue - Mumbai - polymerase chain reaction