Epidemiological and Evolutionary Analysis of Dengue-1 Virus Detected in Guangdong during 2014: Recycling of Old and Formation of New Lineages.

The incidence of dengue is increasing in Guangdong, China, with the largest outbreak to date in 2014. Widespread awareness of epidemiological and molecular characteristics of the dengue virus (DENV) is required. In 2014, we isolated the virus from patients and sequenced its genome. The sequences of DENV isolated from Guangdong and other countries screened since 2005 were studied to establish molecular evolutionary databases along with epidemiological data to explore its epidemiological, phylogenetic, and molecular characteristics. Causes underlying the occurrence of the dengue epidemic included importation and localization of the virus. The number of indigenous cases significantly exceeded that of imported cases. Dengue virus 1 is the most important serotype and caused the long-term epidemic locally. Based on the data available since 2005, DENV1 was divided into three genotypes (I, IV, and V). Only genotypes I and V were detected in 2014. In 2014, an epidemic involving old lineages of DENV1 genotype V occurred after 2 years of silence. The genotype was previously detected from 2009 to 2011. Genotype I, which caused recent epidemics, demonstrated a continuation of new lineages, and a predictive pattern of molecular evolution since 2005 among the four lineages was present. The DENV isolated from Guangdong was closely related to those causing large-scale epidemics in neighboring countries, suggesting the possibility of its import from these countries. The lack of sufficient epidemiological data and evidence on the local mosquito-borne DENV emphasizes the importance of studying the molecular evolutionary features and establishing a well-established phylogenetic tree for dengue prevention and control in Guangdong.

Molecular characterization and phylogenetic analysis of dengue virus type 1 in Guangdong in 2014.

BACKGROUND: Dengue is one of the most important emerging diseases of humans, with no preventive vaccines or antiviral cures available currently. In 2014, the Southeast Asian region experienced an unprecedented outbreak of dengue, especially in Guangdong, China. RESULTS: The nucleotide sequences of the E gene from 23 patients sera of dengue virus type 1 (DENV-1) from Guangzhou, China, were determined. One isolate that was recovered from a patient with serious liver damage was designated GZ02. The whole genome sequence of GZ02 was amplified, and confocal microscopy and plaque reduction neutralization test were performed to investigate the replication kinetics in liver L02 cells. In the study, assembly and genetic comparisons showed 11 of those E gene nucleotide sequences were absolutely accordant, and the nucleic acid sequence divergence among the other strains had no marked difference. CONCLUSIONS: Phylogenetic analysis based on the E gene indicated that the 23 new strains were closely related to strains from Malaysia or Singapore. Two different genotypes (genotype I and III) of DENV-1 were co-circulating in Guangdong, Malaysia, and Singapore from 2013 to 2014. However, no recombination event was found after 2005 between DENV strains from Guangdong and Malaysia or Singapore. GZ02 had a significant replicative advantage over DG14 and the DV1 standard strain. Importation of DENV-1 from Southeast Asian countries may have been an important contributing factor to the 2014 outbreak in Guangdong.

[Study on two strains of mouse developing dampness-heat models infected by Dengue virus].

OBJECTIVE: To establish two strains of mouse developing dampness-heat syndrome models infected by Dengue virus and to compare the difference in infection, so as to choose a suitable mouse strain for modeling. METHODS: According to the modeling methods of the seasonal febrile disease of the dampness-heat syndrome in Chinese medicine, BALB/C and C57BL/6 mice were respectively treated with complex factors as the high glucose and high fat forage + high-temperature chamber + Dengue virus. At the same time a normal control group, the virus infection group (modeled by Dengue virus infection), and the dampness-heat group (modeling by pure dampness heat circumstance) were set up. Changes of the body temperature, platelet counts, virus in the separate serum, pathological changes of the liver, and serological indicators were observed to compare the modeling difference. RESULTS: After modeling low-grade fever appeared in mice in the high-temperature chamber. Compared with the normal control group, the platelet count decreased in mice of the BALB/C model group. AST increased in both BALB/C and C57BL/6 mice and the virus infection group. TC and TG increased in BALB/C model group and the dampness-heat group, with statistical significance (P<0.05). Various degrees of pathological changes were shown in the liver tissue of each group, with the most severe one in the BALB/C model group. The serum virus titers were detected with Real-time PCR after modeling. The virus load was 2.9 x 10(4) - 5.5 x 10(4) copies/mL. No significant difference was found among these groups. CONCLUSIONS: The mouse model of dampness-heat syndrome infected by Dengue virus was primarily established. When compared the infection between BALB/C mice and C57BL/6 mice, BALB/C mice were more suitable for modeling.