Co-circulation of the dengue with chikungunya virus during the 2013 outbreak in the southern part of Lao PDR

Abstract

BackgroundDuring the 2013 outbreak, 4638 infection cases and 32 deaths have been recorded in the southern part of Laos. In recent years, the chikungunya virus (CHIKV) emerged in the part of the country bordering Cambodia. Dengue virus (DENV) and CHIKV are transmitted by common mosquito vectors. Both diseases have similar clinical presentations; therefore, CHIKV infections might go undiagnosed in DENV-endemic areas. Thus, rapid detection and accurate diagnosis are crucial for differentiating between the two viruses (DENV and CHIKV). In this study, we demonstrated that CHIKV and two serotypes of DENV are circulating in Laos. In addition, we encountered patients that had been concurrently infected with multiple DENV serotypes or DENV and CHIKV.MethodsPlasma samples were collected from 40 patients with suspected DENV infections during an outbreak between July and August 2013. The reverse transcription polymerase chain reaction was performed to detect the four DENV serotypes and CHIKV using specific primers. Specifically, the complete envelope gene sequences of the viruses were sequenced and subjected to phylogenetic analysis.ResultsForty acute-phase plasma samples from patients with suspected dengue infections were tested for the presence of DENV viral RNA using molecular methods. Among the 40 samples, 14 samples were positive for DENV, 2 samples were positive for both viruses (DENV-2 and DENV-3), whereas DENV-1 and DENV-4 were not detected during the study period. We also encountered 10 samples that were positive for CHIKV. Of the 10 CHIKV-positive samples, 3 samples were co-infected by DENV-2, and 2 samples were co-infected by DENV-3. Phylogenetic analysis revealed that the 2013 dengue outbreak in Laos involved DENV-2 genotype Asian I and DENV-3 genotype II. Moreover, the Laotian CHIKV strains grouped together with those isolated during outbreaks on the Indian Ocean Islands within the East Central South African genotype.ConclusionsThese findings revealed that two serotypes (DENV-2 and DENV-3) and CHIKV were detected. Furthermore, infection of multiple DENV serotypes and CHIKV was also observed in the 2013 dengue outbreak. This is the first documented evidence of co-infection with CHIKV and one of two DENV serotypes.

Assessment of diagnostic and analytic performance of the SD Bioline Dengue Duo test for dengue virus (DENV) infections in an endemic area (Savannakhet province, Lao People's Democratic Republic)

“…On-site routine diagnostic testing was performed for all febrile patients enrolled in the study in 2013 using the FTD tropical fever core multiplex real-time PCR kit simultaneously testing for dengue virus, chikungunya virus, west nile virus, Plasmodium spp., Rickettsia spp., Leptospira spp., and Salmonella spp.. Although co-circulation/co-infection of dengue and chikungunya virus was detected in samples originating from Champasak province during the 2013 DF outbreak in southern Lao PDR [9], no co-infections with CHIKV were observed in the DF patients enrolled in our study. During the 2013 study period, only one out of 172 febrile patients admitted to Savannakhet Provincial Hospital was found to be CHIKV PCR-positive.…”

“…An infection with DENV1 was found only in two out of 99 patients with an assignable DENV serotype and no DENV4 cases were seen in 2013. Similarly, only DENV2 and DENV3 serotypes were detected during the 2013 DF outbreak in Champasak province (southern Laos) [9]. In the later phase of the study Table 2 IgG antibodies recognizing DENV antigens were detectable by the in-house DENV IgG IIFT in 74% (68/92) of acute phase serum samples (Fig 2) indicating a high percentage of secondary DENV infections in the Lao PDR study collective [6].…”

“…Major limitations of the presented study are the relatively low case number and the strong bias to the two major DENV serotypes (DENV2, DENV3) found in the southern part of Lao PDR during the 2013 epidemics [9].…”

“…In resource-poor settings, lateral flow based point-of-care tests (as the SD Bioline Dengue Duo test) may be the only option to investigate those parameters because they do not require expensive technical equipment and are not affected by adverse storage temperature conditions [7]. Here, we assess the analytical and diagnostic sensitivity of this rapid test using sera from patients with a PCR-confirmed DENV infection from an endemic region in Southeast Asia (Savannakhet province, Lao PDR) [8,9].…”

Serological and spatial analysis of alphavirus and flavivirus prevalence and risk factors in a rural community in western Kenya

“…Given the extremely low number of participants seropositive for previous flavivirus exposure, we believe the overlapping seropositives for both alphaviruses and flaviviruses could provide evidence of saturation of alphavirus exposure in this area. Co-infection of specifically CHIKV and DENV have been reported in mosquitoes and humans during a number of overlapping outbreaks[ 23 , 52 – 54 ], and in mosquitoes via artificial oral exposure in a laboratory setting[ 55 ]. Yet, others suggest that competitive suppression occurs when cultured mosquito cells are co-infected with CHIKV and DENV[ 56 ], which may explain the regional variability of alphavirus and flavivirus prevalence that has been continually reported throughout Kenya[ 2 , 20 – 22 ].…”