Dengue in Santander State, Colombia: fluctuations in the prevalence of virus serotypes are linked to dengue incidence and genetic diversity of the circulating viruses.

OBJECTIVE: To investigate the link between fluctuations in the prevalence of dengue virus (DENV) serotypes and the number of dengue cases in the metropolitan area of Bucaramanga, Santander State, Colombia, in the 2007-2010 and 2014-2017 periods. METHOD: Viruses were isolated from febrile patient samples by direct application to C6/36-HT cells and typed using monoclonal antibodies. We performed autocorrelation and cross-correlation analyses to determine whether fluctuations in the prevalence of DENV serotypes and dengue cases were correlated. Full envelope (E) gene sequences were employed to examine the genetic diversity of serotypes circulating by using a phylogenetic approach. RESULTS: All four dengue virus serotypes were detected. DENV-1 was the dominant serotype in both periods followed by DENV-3 or DENV-2 depending on the period; DENV-4 was the least prevalent virus in both periods. Cross-correlation analyses suggest a temporal relation between the fluctuations in the prevalence of DENV serotypes, which were almost simultaneous (lag = 0) or related to recent past fluctuations (lag > 1.0) in the number of dengue cases. Data suggest that a sustained predominance of DENV-1, an increase of the DENV-4 prevalence, and a switch from DENV-3 to DENV-2 could be linked to an outbreak. Circulating viruses were grouped into Genotype V, Asia/American III and II for DENV-1, -2, -3 and -4, respectively; intragenotypic diversity was detected. CONCLUSIONS: The present work highlights the need of comprehensive studies on dynamics of DENV in Colombia to understand transmission of dengue and evaluate the effectiveness of a vaccination programme.

OBJECTIF: Etudier le lien entre les fluctuations de la prévalence des sérotypes du virus de la dengue (DENV) et le nombre de cas de dengue dans la région métropolitaine de Bucaramanga, dans l'Etat de Santander, en Colombie, au cours des périodes 2007-2010 et 2014-2017. MÉTHODE: Les virus ont été isolés à partir d'échantillons de patients fébriles par application directe sur des cellules C6/36-HT et typés à l'aide d'anticorps monoclonaux. Nous avons effectué des analyses d'autocorrélation et de corrélation croisée afin de déterminer si les fluctuations de la prévalence des sérotypes du DENV et des cas de dengue étaient corrélées. Des séquences de gènes d'enveloppe complète (E) ont été utilisées pour examiner la diversité génétique des sérotypes en circulation en utilisant une approche phylogénétique. RÉSULTATS: Tous les quatre sérotypes du virus de la dengue ont été détectés. DENV-1 était le sérotype dominant dans les deux périodes, suivi de DENV-3 ou DENV-2, selon la période; le virus DENV-4 était le moins prévalent au cours des deux périodes. Les analyses de corrélation croisée suggèrent une relation temporelle entre les fluctuations de la prévalence des sérotypes de DENV, qui étaient presque simultanées (lag = 0) ou liées aux fluctuations passées récentes (lag > 1,0) du nombre de cas de dengue. Les données suggèrent qu'une prédominance durable de DENV-1, qu'une augmentation de la prévalence de DENV-4 et qu'un passage de DENV-3 à DENV-2 pourraient être liés à une éclosion. Les virus en circulation ont été regroupés dans les génotypes V, Asie/Amérique III et II pour DENV-1, -2, -3 et -4, respectivement; une diversité intra-génotypique a été détectée. CONCLUSIONS: Le présent travail souligne la nécessité d'études approfondies sur la dynamique du DENV en Colombie afin de comprendre la transmission de la dengue et évaluer l'efficacité d'un programme de vaccination.

Selective interhemispheric circuits account for a cardinal bias in spontaneous activity within early visual areas.

Ongoing brain activity exhibits patterns resembling neural ensembles co-activated by stimulation or task performance. Such patterns have been attributed to the brain's functional architecture, e.g. selective long-range connections. Here, we directly investigate the contribution of selective connections between hemispheres to spontaneous and evoked maps in cat area 18 close to the 17/18 border. We recorded voltage-sensitive dye imaging maps and spiking activity while manipulating interhemispheric input by reversibly deactivating corresponding contralateral areas. During deactivation, spontaneous maps continued to be generated with similar frequency and quality as in the intact network but a baseline cardinal bias disappeared. Consistently, neurons preferring either horizontal (HN) or vertical (VN), as opposed to oblique contours, decreased their resting state activity. HN decreased their rates also when stimulated visually. We conclude that structured spontaneous maps are primarily generated by thalamo- and/or intracortical connectivity. However, selective long-range connections through the corpus callosum - in perpetuation of the long-range intracortical network - contribute to a cardinal bias, possibly, because they are stronger or more frequent between neurons preferring horizontal and/or cardinal contours. As those contours are easier perceived and appear more frequently in natural environment, long-range connections might provide visual cortex with a grid for probabilistic grouping operations in a larger visual scene.