Co-Circulation of Dengue Serotypes in Coastal Andhra Pradesh, India - A Descriptive Study

BACKGROUND Dengue is an acute febrile illness caused by mosquito-borne dengue viruses (DENV S) consisting of four serotypes (DENV 1 - 4) from flaviviridae family, genus flavivirus. These four are antigenically related serotypes designated as DEN V - 1, DEN V - 2, DEN V - 3 and DEN V – 4. In this context, the present study focuses on the circulating serotypes of dengue in coastal Andhra Pradesh. METHODS Study was done at Andhra Medical College, Visakhapatnam, teaching hospital in Andhra Pradesh. Acute phase dengue serum samples were collected and tested for NS1 antigen and antihuman IgM antibodies by enzyme linked –immunosorbent assay (ELISA). NS1 positive samples were further serotyped by reverse transcriptase real time polymerase chain reaction (R RT - PCR). RESULTS A total of 796 serum samples were included in the study. 300 (37.7 % ) samples were positive for NS1 and IgM antibodies. 192 NS1 antigen positive samples were further processed for serotyping by r RT PCR. Among these samples 72 were negative by r RT PCR. DENV-2 (41 %) was the predominant serotype followed by DENV-4 (37 %), DENV-3 (12 %) and DENV-1 (10 %) in the descending order. CONCLUSIONS All the four dengue serotypes are in co-circulation. Among all the four types, DENV-2 was predominant, followed by DENV-4. By knowing the predominant serotype in circulation, we can forecast dengue outbreaks and take necessary measures like control of vectors. KEY WORDS Andhra Pradesh, Dengue Virus, Dengue Virus - 2, Dengue Virus - 4, Outbreak, Serotypes