All four dengue serotypes cause infection, with one of them predominantly reported from a particular geographical region. Coinfection by more than one serotype is reported from hyperendemic regions. These coinfections are clinically more severe than infection with a single serotype. This study was carried out to detect the predominant dengue serotype and presence of coinfections.

Prevalence of dengue co-infections is increasing. Moreover, it is important to screen for dengue virus in those samples also which do not show NS1Ag on rapid tests and have either one or both the antibodies. Real-time multiplex RT-PCR is found to be more sensitive in detecting coinfection than conventional multiplex RT-PCR.

Acute-phase serum samples of patients suffering from dengue infection were collected. They were screened for the presence of IgM, IgG and NS1Ag by a rapid test. Conventional multiplex reverse transcriptase polymerase chain reaction (RT-PCR) and multiplex real-time RT-PCR assays were carried out for detection and serotyping of the dengue virus.

A total of 196 samples were positive by the rapid card test. Of these, 139 were NS1Ag positive, 40 were positive only for IgM, 5 were positive only for IgG and 12 samples were positive for different combinations of antigen and antibodies. All four serotypes were detected in these samples by PCR. DENV-3 was found to be most common circulating serotype. A total of 22 cases were found to have coinfection with more than one dengue serotypes. Samples having only antibodies and no antigen on rapid card test were also positive for virus by PCR.