Emergence and global spread of a dengue serotype 3, subtype III virus

Over the past two decades, dengue virus serotype 3 (DENV-3) has caused unexpected epidemics of dengue hemorrhagic fever (DHF) in Sri Lanka, East Africa, and Latin America. We used a phylogenetic approach to evaluate the roles of virus evolution and transport in the emergence of these outbreaks. Isolates from these geographically distant epidemics are closely related and belong to DENV-3, subtype III, which originated in the Indian subcontinent. The emergence of DHF in Sri Lanka in 1989 correlated with the appearance there of a new DENV-3, subtype III variant. This variant likely spread from the Indian subcontinent into Africa in the 1980s and from Africa into Latin America in the mid-1990s. DENV-3, subtype III isolates from mild and severe disease outbreaks formed genetically distinct groups, which suggests a role for viral genetics in DHF.     

Re-emergence of Anopheles funestus and its possible effect on malaria transmission on Mayotte Island, Indian Ocean

Malaria constitutes a major public health problem on Mayotte Island, with the major vector being Anopheles gambiae s.s. The seeming disappearance of An. funestus, the 2nd vector on the island, was observed 15 years ago. Now, the presence of An. funestus during the biting collections performed in November and December 2004 confirms the re-emergence of this vector, which plays an important role in malaria transmission with An. gambiae.     

Socio-demographic and behavioral determinants of hepatitis B vaccination and infection in pregnant women on Mayotte Island,Indian Ocean

Background

Socio-demographic and behavioral determinants of Hepatitis B virus (HBV) vaccination and infection among pregnant women (PW) of Mayotte Island (Indian Ocean) are not well understood.

Methods

Six hundred and seventy-one pregnant women presenting to public antenatal clinics on Mayotte Island were included between September 15, 2008 and September 27, 2009. Socio-demographics, sexual risk behavior characteristics, and data for HBV biomarkers were collected. Logistic regression was undertaken to study determinants of HBV vaccination and factors associated with the risk of HBV infection were assessed using a survival method adapted to interval-censored data. Due to missing data for HBV biomarkers, data were analyzed using multiple imputation (MI).

Results

Past or recent HBV infection was observed for 35.5% (95% confidence interval (CI): 30.4–40.8) of PW and 18.6% (95% CI: 14.7–23.2) had evidence of HBV vaccination. PW with unemployed and education qualification (adjusted odds ratio (aOR) 2.65, 95% CI 1.52–4.60) and student status (aOR 4.79, 95% CI 1.63–4.07) were better vaccinated against HBV, compared to those without employment and education. Being born on Comoros was associated with a 63% reduction in HBV vaccination (aOR 0.37, 95% CI 0.21–0.65), compared to be born in Mayotte/France. Women with a history of sexually-transmitted infections in the last 5 years had an increased risk of HBV infection (adjusted hazard ratio (aHR) 3.10, 95% CI: 1.13–8.50), whereas those who sometimes used condoms had a 60% reduced risk (aHR = 0.40, 95% CI: 0.23–0.69).

Conclusions

Socio-demographic factors were identified for HBV vaccination, while behavioral factors were observed for HBV infection. These results could help to determine priorities for intervention.     

Outbreak of measles in Mayotte, Indian Ocean, 2005-2006

Objective

An outbreak of measles occurred from 2005 to 2006 in Mayotte, a French territory in the Indian Ocean. The aim of this study was to describe the outbreak, to analyze epidemiologic and sociodemographic characteristic of cases, and to suggest recommendations for measles surveillance and preventive measures in Mayotte.

Design

An outbreak investigation was conducted and an enhanced passive surveillance system of incident cases was implemented.

Results

During the outbreak, 1269 clinical cases, including 156 (12.3%) biologically confirmed cases, were reported. The attack rate was 0.71% and no death due to measles was recorded. The median age of cases was 12 years and the M/F sex-ratio 1.1. Teenagers and young adults (10–19 years) were the most frequently affected (44.4%) and infants less than one year of age accounted for 21.6% of the cases. In the 1269 clinical cases, 27.3% of patients had received at least one dose of measles vaccine before the outbreak. The immunization coverage in school children reached 59.1% at the end of the vaccination campaign.

Conclusion

In the future, this vaccinal coverage should be improved to prevent other outbreaks, especially in vulnerable groups like immigrants. A surveillance system with systematical report of the biologically confirmed cases is needed in Mayotte.     

Emergence of multireassortant bluetongue virus serotype 4 in Hungary

The genome sequence and the phylogenetic relationships of a serotype 4 bluetongue virus (BTV-4) emerged during 2014 in Hungary are described in this study. Genome segment 2 encoding the major neutralization antigen, VP2, shared moderate sequence similarity (nt, ⩽94.3%) with the corresponding gene of contemporary and historic homotypic bluetongue viruses, whereas genome segments S1, S4, S5, S7–S10 were typically more closely related to the cognate genes of heterotypic isolates. Importantly, in many gene phylogenies the Hungarian BTV-4 strain showed genetic relationship to BTV strains identified in outbreaks in the western Mediterranean basin. Our results indicate the identified Hungarian bluetongue virus strain evolved through reassortment involving multiple genome segments from various heterotypic bluetongue viruses.     

Genetic diversity and evolution of dengue virus serotype 3: A comparative genomics study

Dengue virus serotype 3 (DENV-3), one of the four serotypes of Dengue viruses, is geographically diverse. There are five distinct genotypes (I–V) of DENV-3. Emerging strains and lineages of DENV-3 are increasingly being reported. Availability of genomic data for DENV-3 strains provides opportunity to study its population structure. Complete genome sequences are available for 860 strains of four genotypes (I, II, III and V) isolated worldwide and were analyzed using population genetics and evolutionary approaches to map landscape of genomic diversity. DENV-3 population is observed to be stratified into five major subpopulations. Genotype I and II formed independent subpopulations while genotype III is subdivided into three subpopulations (GIII-a, GIII-b and GIII-c) and is therefore heterogeneous. Genotypes I, II and GIII-a subpopulations comprise of Asian strains whereas GIII-c comprises of American strains. GIII-b subpopulation includes mainly of American strains along with a few strains from Sri Lanka. Genetic admixture is predominantly observed in Sri Lankan strains of genotype III and all strains of genotype V. Inter-genotype recombination was observed to occur in non-structural region of several Asian strains whereas extent of recombination was limited in American strains. Significant positive selection was found to be operational on all genes and observed to be the main driving force of genetic diversity. Positive selection was strongly operational on the branches leading to Asian genotypes and helped to delineate the genetic differences between Asian and American lineages. Thus, inter-genotype recombination, migration and adaptive evolution are the major determinants of evolution of DENV-3.     

Epidemiology of Chikungunya infection on Reunion Island, Mayotte, and neighboring countries

Since 2004, the frequency of chikungunya virus infections has been increasing in Africa, Indian Ocean islands, and Asia. The epidemic began on the Kenyan coast, and reached the Comoros at the end of 2004 before spreading to the South-western Indian Ocean islands (SWIOI) in 2005 and especially in 2006. The epidemic then spread to Asia where epidemic foci are still active today. This increase also affected temperate zone countries where imported cases were reported, and indigenous transmission was reported in Italy in 2007, and in France (Var) in 2010. This review provides an update on the knowledge gained from monitoring chikungunya infections in SWIOI. Despite significant differences in design and performance, the implementation of surveillance systems has allowed describing the evolution of epidemic waves in the affected areas. Synchronous epidemic waves were observed in SWIOI, despite the differences between the preventive measures locally implemented. Between 2005 and 2007, all SWIOI were in inter-epidemic situation, except for Madagascar where a persistent virus circulation in an endemic-epidemic pattern was observed. In 2009, and in 2010, two moderate indigenous outbreaks were identified on the Reunion Island by the inter-epidemic surveillance system. Strains analyses demonstrated a reintroduction of the virus from Madagascar. These limited outbreaks should be a reminder of the vulnerability of SWIOI to arbovirosis, since the entomological indexes for competent vectors are high and the virus keeps on circulating more or less actively in the area.     

Characterization of the 2013 dengue epidemic in Myanmar with dengue virus 1 as the dominant serotype

In 2013 in Myanmar, dengue epidemic occurred with 20,255 cases including 84 deaths. This study aimed to determine the serological and molecular characteristics of dengue virus (DENV) infection among children with clinical diagnosis of dengue hemorrhagic fever (DHF) or dengue shock syndrome (DSS) during this period. Single acute serum samples were collected from 300 children in Mandalay Children Hospital, Mandalay, Myanmar. Out of the 300 children, 175 (58.3%) and 183 (61%) were positive for anti-dengue IgM and anti-dengue IgG, respectively. Among the IgM positives, 41 (23.4%) had primary DENV infection. Thirty-nine DENV strains (23 DENV-1, 10 DENV-2 and 6 DENV-4) were successfully isolated after inoculation of the patient serum samples onto C6/36 cells. DENV 1 was the dominant serotype in the 2013 epidemic. There was no correlation between the infecting serotypes and clinical severities. The DENV-1 strains belonged to three lineages of the genotype 1; the DENV-2 strains were of the Asian I genotype and were separated into two lineages; and DENV-4 strains belonged to the same lineage of genotype I. It is of interest to note the diversity of DENV-1 and -2 circulating in the same location during June–August 2013. These DENV isolates were genetically close (98%–100%) to the other previously reported isolates from Myanmar and its neighboring countries, namely China, Thailand, Sri Lanka, Cambodia and Vietnam. Primary DENV infection was still high among the severe dengue cases. Different serotypes of DENV were co-circulating in 2013, however, genotype shift was not observed. Additionally, amino acid mutations were detected in the study strains not seen in the previously reported strains from other countries and Myanmar. This paper provided information on the circulating serotypes for the last 15 years and the recent dengue situation in Mandalay, Myanmar after 2006.     

Emergence of serotype G12 rotaviruses, Hungary

We describe the emergence of serotype G12 rotaviruses (67 [6.9%] of 971 specimens tested) among children hospitalized with rotavirus gastroenteritis in Hungary during 2005. These findings are consistent with recent reports of the possible global spread and increasing epidemiologic importance of these strains, which may have implications for current rotavirus vaccination strategies.     

广州市2010-2019年4型登革热病例流行特征及其病毒E基因

目的  了解2010-2019年广州市4型登革热病例的流行病学特征和4型登革病毒的分子生物学特征。方法  2010-2019年,收集广州市登革热病例相关资料及血清标本,使用RT-PCR法检测血清标本并分型,对4型登革热病例标本进行登革病毒包膜(envelope, E)蛋白基因序列测定,并进行进化树构建及基因重组分析。结果  2010-2019年,广州市共报告43 174例登革热病例,其中23例为4型登革热病例。4型登革热病例仅分布在5个区,曾在2010年出现本地流行。广州市的4型登革热输入病例主要来自东南亚国家,病毒E基因序列与东南亚国家的序列有较高相似性,病毒基因型归属于印度尼西亚基因型和东南亚基因型,未检测到基因重组。结论  应加强对广州市4型登革热病例流行状况和输入病例的监测和关注,并进一步加强对东南亚回国人员登革热常识和个人防护的健康宣传。某些区需要预防出现4型登革病毒的扩散和蔓延。登革病毒基因型转换并未引起登革热在广州市流行强度的变化,有待进一步的观察和研究其是否会发生重组。     

Genome analysis of Rift Valley fever virus, Mayotte

As further confirmation of a first human case of Rift Valley fever in 2007 in Comoros, we isolated Rift Valley fever virus in suspected human cases. These viruses are genetically closely linked to the 2006-2007 isolates from Kenya.     

广州市2001-2015年登革病毒2型E基因进化分析

目的 了解2001-2015年广州市登革病毒2型（DENV2）的流行情况;通过对分离DENV2 E基因的进化树和分子钟分析,掌握毒株的进化情况和趋势。方法 将登革热确诊病例的血清用荧光PCR进行检测,DENV阳性血清用C6/36细胞进行病毒分离,测定分离毒株的E基因序列,利用Mega 4.0软件构建进化树,采用BEASTv1.8.2绘制分子进化钟。结果 2001-2015年共分离到26株DENV2,从基因型上分类属于全球型和亚洲1型,并与东南亚地区分离到的毒株相似率较高;BEASTv1.8.2计算出广州市DENV2全球型在46年前和35年前进一步出现亚型的分化,广州市DENV2的平均变异率为每年每位点7.1×10^-4。结论 广州市DENV2与东南亚地区的毒株有较高同源性和进化上的联系,广州市DENV的输入压力较大,存在重症登革热暴发的潜在风险。流行于广州市的全球型DENV2可能存在2个不同输入来源,广州市DENV2的变异率与周边地区基本持平。     

Dengue virus 3 genotype 1 associated with dengue fever and dengue hemorrhagic fever, Brazil

Dengue serotype 3 viruses were isolated from patients in Brazil from 2002 through 2004. On the basis of phylogenetic analyses, these isolates were assigned genotype 1. This genotype had never been reported in South America before. Its appearance indicates a major risk factor for dengue epidemics and severe disease.     

The invaders: Phylogeography of dengue and chikungunya viruses Aedes vectors, on the South West islands of the Indian Ocean

Aedes albopictus and Aedes aegypti are the two main worldwide arbovirus vectors that have experienced invasion phases. Aedes aegypti is a pantropical species that spread centuries ago whereas Ae. albopictus started the main wave of invasion in the 1980s. Both species have been at various times on the different islands in Southwestern Indian Ocean (SWIO). This area provides an opportunity to examine the extent to which mosquitoes colonization patterns are influenced by different introductory events likely linked with human settlement and migration between the islands. To explore this hypothesis, we propose a CO1-based phylogeny using a large sampling of fresh Ae. albopictus, Ae. aegypti, and Ae. mascarensis, and 50-year-old dry specimens originating from different Indian Ocean islands.Our data allow us to hypothesize the existence of at least two waves of invasion for Ae. albopictus in the islands of SWIO. The first one most likely occurred several centuries ago with establishments in Madagascar, Mauritius and Reunion Island. The other one that appears to currently still on-going, reached almost all the islands of SWIO during the 1990s or later. The low genetic diversity found between the ancient invasive strain and the contemporary one, indicates with great certainty that Ae. albopictus is not indigenous to the islands of SWIO. Recently, in Madagascar, an invasive lineage of Ae. albopictus has expanded all over the island while Ae. aegypti populations have declined in urban areas. Three clusters of Aedes aegypti have been observed, two fitting with the wild form Ae. aegypti formosus and the other one fitting with the more domestic form Ae. ae. aegypti. Sequence of Ae. mascarensis, endemic to Mauritius suggest that this species might belong to Ae. aegypti species and on this basis we propose to classify it as a sub species or form of Ae. aegypti species.Given the increase of human population flux on these islands, the occurrence of these vectors and their ability to spread quickly are of high importance of arbovirus transmission and the epidemicity of the associated diseases in these islands.     

Novel chikungunya virus variant in travelers returning from Indian Ocean islands

Chikungunya virus (CHIKV) emerged in Indian Ocean islands in 2005 and is causing an ongoing outbreak that involves >260,000 patients, including travelers returning home from these islands. We investigated cases in 4 patients returning from Mayotte and Reunion Islands with CHIKV infection and a nurse infected in metropolitan France after direct contact with the blood of a traveler. Four patients had tenosynovitis and pain at wrist pressure, and 1 had life-threatening manifestations. Four CHIKV strains were isolated, including 1 from the patient with the autochthonous case. The complete genomic sequence identified a new CHIKV variant emerging from the East/ central African evolutionary lineage. Aedes albopictus, the implicated vector of CHIKV in Indian Ocean islands, has dispersed worldwide in recent decades. High viral loads in patients returning from Indian Ocean islands to countries where Ae. albopictus is prevalent may be a source of epidemics.