Co-circulation of dengue virus type 3 genotypes in Vientiane capital, Lao PDR.

During the 2012 epidemic of dengue in Vientiane capital, Lao PDR, a major serotype switch from dengue 1 to 3 was observed. A molecular epidemiology study demonstrated that dengue 3 remained the predominant serotype in 2013, but also revealed the co-circulation of two genotypes, supporting the hypothesis of multiple geographic origins of dengue 3 strains circulating in Vientiane capital

Genetic signatures displayed by the CHIKV Lao isolates over the studied period (August 2012–December 2013).

<p>Genetic signatures displayed by the CHIKV Lao isolates over the studied period (August 2012–December 2013).</p

Chikungunya virus emergence in the Lao PDR, 2012–2013

<div><p>In May 2012, the first authenticated cases of active chikungunya virus infection were detected in Champasak Province, Southern Laos. Analysis of series of human samples and mosquito specimens collected during the outbreak and over the year that followed the emergence enabled the drawing up of a map of the progression of CHIKV and the establishment of a full genetic characterization of the virus.</p></div

Virologic markers of CHIKV infection recorded in suspected cases recorded during the initial field investigation in August 2012.

<p>Virologic markers of CHIKV infection recorded in suspected cases recorded during the initial field investigation in August 2012.</p

Distribution of Chikungunya virus vectors and mosquito species composition from adult and larval collections in villages visited during the initial field investigation in August 2012 (see Fig 1A).

<p>Distribution of Chikungunya virus vectors and mosquito species composition from adult and larval collections in villages visited during the initial field investigation in August 2012 (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0189879#pone.0189879.g001" target="_blank">Fig 1A</a>).</p

Chikungunya virus study sites in 2012–2013.

<p>1A) Entomologic surveillance sites in September 2012. Black triangles represent villages in Moonlapamok and Khong Districts. Red stars represent villages where mosquito larvae were sampled. 1B) Chikungunya virus IgM seroprevalence in villages in Moonlapamok District. 1C) Chikungunya virus IgM seroprevalence in villages in Khong District. Letters correspond to the villages’ code and numbers to the recorded seroprevalence level.</p

Main symptoms recorded declared by the volunteers during the retrospective seroprevalence study in 2013.

<p>Main symptoms recorded declared by the volunteers during the retrospective seroprevalence study in 2013.</p

Phylogenetic relationships of DENV-3 based on the complete E nucleotide sequences (1479 nt) of 41 isolates, including 16 Lao isolates.

<p>Blue triangles and blue circles represent Lao DENV-3 genotype II and III strains respectively. Sequence alignments were performed using BioNumerics version 6.6. A maximum-Likelihood tree was constructed using MEGA version 6, based on Tamura-Nei model. Bootstrap resampling values are indicated at major nodes. Scale bar indicates number of base substitutions per site.</p

List of studied Lao DENV-3 isolates.

<p>List of studied Lao DENV-3 isolates.</p

Surveillance performed by Institut Pasteur du Laos from March 2012 to December 2013.

<p>(A) Distribution of confirmed cases (i.e. RT-PCR and/or NS1 and/or culture positive) in Vientiane city (B). Dengue serotypes distribution in 2012 and 2013. Recording of dengue serotypes distribution on a four monthly basis. As the surveillance only started in late March 2012, partial data collected in April were not included in the figure.</p