Genetic diversity and population structure of Aedes aegypti after massive vector control for dengue fever prevention in Yunnan border areas.

Dengue fever is a mosquito-borne disease caused by the dengue virus. Aedes aegypti (Ae. Aegypti) is considered the primary vector of Dengue virus transmission in Yunnan Province, China. With increased urbanization, Ae. aegypti populations have significantly increased over the last 20 years. Despite all the efforts that were made for controlling the virus transmission, especially on border areas between Yunnan and Laos, Vietnam, and Myanmar (dengue-endemic areas), the epidemic has not yet been eradicated. Thus, further understanding of the genetic diversity, population structure, and invasive strategies of Ae. aegypti populations in the border areas was vital to uncover the vector invasion and distribution dynamic, and essential for controlling the infection. In this study, we analyzed genetic diversity and population structure of eight adult Ae. Aegypti populations collected along the border areas of Yunnan Province in 2017 and 2018. Nine nuclear microsatellite loci and mitochondrial DNA (mtDNA) sequences were used to achieve a better understanding of the genetic diversity and population structure. One hundred and fourteen alleles were found in total. The polymorphic information content value, together with the expected heterozygosity (He) and observed heterozygosity (Ho) values showed high genetic diversity in all mosquito populations. The clustering analysis based on Bayesian algorithm, the UPGMA and DAPC analysis revealed that all the eight Ae. aegypti populations can be divided into three genetic groups. Based on the mtDNA results, all Ae. aegypti individuals were divided into 11 haplotypes. The Ae. aegypti populations in the border areas of Yunnan Province presented with high genetic diversity, which might be ascribed to the continuous incursion of Ae. aegypti.

A COVID-19 case report from asymptomatic contact: implication for contact isolation and incubation management.

BACKGROUND: As of 2 March, 2020, at least 80 151 coronavirus disease 2019 (COVID-19) cases were reported in China. Most of the patients had a history of visiting Hubei Province or contacting with people who had ever stayed in or passed by Hubei Province or were exposed to symptoms. Some patients got infected through only asymptomatic contact. This study aimed to report the epidemic features and lab identification of a patient confirmed with COVID-19 infection through only asymptomatic contact. CASE PRESENTATION: A 44-year-old man, who lived in Nanchang, Jiangxi Province, China until 6 March 2020, suffered from cough on 27 January 2020. Fever symptoms appeared on 28 January, with a maximum temperature of 38.8 °C, accompanied by cough, sore throat, headache, fatigue, muscle ache, joint ache, and other symptoms. The symptoms continued until he was hospitalized on 30 January. Coronavirus conventional polymerase chain reaction assay was positive for the throat swab sample. The patient, along with his wife and son, drove from Nanchang to back to Honghu City, Hubei Province, on 23 January 2020. After staying with his parents and brother's family for 3 days, the patient drove back to Nanchang and arrived on 25 January. On the way back home, they stopped by Tongshan service area, Hubei Province, without any close contact with other people. After arriving home in Nanchang City, Jiangxi Province, none of them left their residence. In addition, his parents stayed at home for 20 days with his younger brother's family before they got back. His younger brother and one of his brother's children visited Wuhan on 5 January and came home on 6 January 2020. CONCLUSIONS: This report suggested that, in the early phase of COVID-19 pneumonia, routine screening could miss patients who were virus carriers. Highlighting travel history is of paramount importance for the early detection and isolation of severe acute respiratory syndrome coronavirus 2 cases.

Correction to: The polymorphism and geographical distribution of knockdown resistance of adult Anopheles sinensis populations in eastern China.

Please be advised that since publication of the original article [1] the authors have flagged that they omitted to provide the up-to-date version of Fig. 1 and, as such, the wrong version of Fig. 1 is present in the article.

The polymorphism and geographical distribution of knockdown resistance of adult Anopheles sinensis populations in eastern China.

BACKGROUND: Anopheles sinensis is one of the major malaria vectors in China and other southeast Asian countries, including Vietnam, Cambodia, Thailand. Vector control is considered to be the critical measure for malaria control, while the increasing prevalence of insecticide resistance caused by long-term use of insecticides, especially pyrethroids, is threatening the successful control of An. sinensis. In order to understand the underlying resistance mechanisms involved and molecular basis, the principal malaria vector, An. sinensis from Jiangsu and Anhui provinces, Southeast China, was investigated. METHODS: The adult Anopheles mosquitoes were sampled from multiple sites across Jiangsu and Anhui provinces, and sufficient mosquitoes collected from eleven sites for insecticide susceptibility bioassays. The DIIS4-DIIS6 region of the para-type sodium channel gene was amplified and sequenced, then multiple PCR and Taqman assays were used to assess the frequencies of kdr mutations at the target gene. RESULTS: In the present study, most of the adult An. sinensis populations were pyrethroids resistant, which indicated the presence of kdr resistance mutations in the para-type sodium channel gene. Sequence analyses demonstrated the kdr mutation existed at codon 1014 in Jiangsu and Anhui provinces. In adult An. sinensis, three mutant types (TTT L1014F, TTC L1014F, and TGT L1014C) of kdr alleles were detected, while no wild type (TTG L1014) was observed. The TTC L1014F mutation was first reported in Anhui province. CONCLUSIONS: The highly polymorphic kdr alleles were observed in all the adult An. sinensis populations, which suggested that in-depth studies are required for carrying on insecticide resistance monitoring and specific resistance mechanisms studying into establish effective long-term malaria vector control program in eastern China.