Shifting of circulating serotypes in dengue outbreaks during 2009/2010 in Sri lanka

Abstract

OBJECTIVES: Sri Lanka has experienced explosive outbreaks of dengue infection in 2009 and 2010. It has been identified that DEN- 3 and DEN- 2 were the predominant serotypes with DEN-1 and DEN- 4 circulating at a lower level in previous dengue outbreaks during 2003-2006, Objective of this study was to identify the circulating serotype/s during 2009 - 2010 outbreaks. METHODOLOGY: A prospective study was carried out at North Colombo Teaching Hospital, Sri Lanka during December 2009-August 2010. Clinically suspected dengue patients, with fever less than 5 days were recruited. An interviewer administered questionnaire was filled for each patient, by a Medical Officer. Venous blood samples confirmed for the presence of dengue virus by RT-PCR were typed by Semi-Nested PCR. RESULTS: Out of the 209 patients recruited in the study 80 (38%) were positive for dengue virus by RT-PCR. Of the positives, 43 (54%) were typed and circulation of all 4 serotypes was observed- Of the 43 positives, presence of DEN-1, DEN-2, DEN-3 and DEN-4 serotypes was 34 (79%), 3 (7%), 2 (5%) and 3 (7%) respectively DEN-1 was the predominant serotype in the recent epidemics which was circulating at a low level in previous epidemics. In DEN-1 infected patients, the mean platelet value was 58,588/ rnm3 and the mean PCV value was 41.4%. Associated symptoms such as headache, retro-orbital pain, neck pain and limb pain were present in 94% (32/34), 59% (20/34), 24% (8/34J and 91% (31/34) patients respectively. Bleeding manifestation developed in 47 % (16/34) patients. The mortality rate ranged from 0.7%- 1.0% during the recent outbreaks. Acknowledgement: Financial and technical assistance from the International Centre for Genetic Engineering and Biotechnology (ICGEB CRP/ SRI08-02) and the International Atomic Energy Agency (IAEA SRI 5/042) is gratefully acknowledged.