https://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(07)61779-6.pdf

Infection with chikungunya virus in Italy: an outbreak in a temperate region

Chikungunya virus (CHIKV) is an emerging arbovirus associated with several recent large-scale epidemics. The 2005–2006 epidemic on Reunion island that resulted in approximately 266,000 human cases was associated with a strain of CHIKV with a mutation in the envelope protein gene (E1-A226V). To test the hypothesis that this mutation in the epidemic CHIKV (strain LR2006 OPY1) might influence fitness for different vector species, viral infectivity, dissemination, and transmission of CHIKV were compared in Aedes albopictus, the species implicated in the epidemic, and the recognized vector Ae. aegypti. Using viral infectious clones of the Reunion strain and a West African strain of CHIKV, into which either the E1–226 A or V mutation was engineered, we demonstrated that the E1-A226V mutation was directly responsible for a significant increase in CHIKV infectivity for Ae. albopictus, and led to more efficient viral dissemination into mosquito secondary organs and transmission to suckling mice. This mutation caused a marginal decrease in CHIKV Ae. aegypti midgut infectivity, had no effect on viral dissemination, and was associated with a slight increase in transmission by Ae. aegypti to suckling mice in competition experiments. The effect of the E1-A226V mutation on cholesterol dependence of CHIKV was also analyzed, revealing an association between cholesterol dependence and increased fitness of CHIKV in Ae. albopictus. Our observation that a single amino acid substitution can influence vector specificity provides a plausible explanation of how this mutant virus caused an epidemic in a region lacking the typical vector. This has important implications with respect to how viruses may establish a transmission cycle when introduced into a new area. Due to the widespread distribution of Ae. albopictus, this mutation increases the potential for CHIKV to permanently extend its range into Europe and the Americas.

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A single mutation in chikungunya virus affects vector specificity and epidemic potential.

Present and future arboviral threats.

Chikungunya is an arboviral disease transmitted by aedes mosquitoes. The virus was fi rst isolated in 1953 in Tanzania. Chikungunya virus is a member of the genus Alphavirus and the family Togaviridae. The disease typically consists of an acute illness characterised by fever, rash, and incapacitating arthralgia. The word chikungunya, used for both the virus and the disease, means “to walk bent over” in some east African languages, and refers to the eff ect of the joint pains that characterise this dengue-like infection. Chikungunya is a specifi cally tropical disease, but it is geographically restricted and outbreaks are relatively uncommon. It is only occasionally observed in travellers and military personnel. More than 266 000 people have been infected during the ongoing outbreak in Reunion, in which Aedes albopictus is the presumed vector. In the ongoing Indian outbreak, in which Aedes aegypti is the presumed vector, 1 400 000 cases of chikungunya were reported during 2006. The reasons for the re-emergence of chikungunya on the Indian subcontinent, and for its unprecedented incidence rate in the Indian Ocean region, are unclear. Plausible explanations include increased tourism, chikungunya virus introduction into a naive population, and viral mutation.

http://antimicrobe.org/h04c.files/history/LancetID_Pialouxetal_Chikugunya,%20an%20Epidemic%20Arbovirus_2007.pdf

Chikungunya, an epidemic arbovirosis.

Arthropod-borne viruses (arboviruses) are the causative agents of some of the most important emerging infectious diseases and are responsible for significant global public health problems (Gubler, 2001). Of these viruses, the genus Alphavirus belongs in the family Togaviridae, and the species in this genus cause diseases ranging from mild febrile illness to severe polyarthritis to encephalitis. One alphavirus, chikungunya virus (CHIKV), caused recent outbreaks associated with severe morbidity. Traditionally, CHIKV causes a febrile illness similar to that seen in dengue virus infections. The hallmark feature of CHIKV disease is a debilitating and prolonged arthralgic syndrome that primarily affects the peripheral small joints. While the acute febrile phase of the illness normally resolves within a few days, the pain associated with CHIKV infection of the joints typically persists for weeks or months causing serious economic and social impact on both the individual and the affected communities. During the 2005–2007 explosive epidemics on the Indian Ocean islands and in India, anecdotal cases of CHIKV-associated deaths, encephalitis and neonatal infections were reported. Here, we review outbreaks of CHIKV disease and present a comprehensive analysis and comparison of clinical presentation, virus– vector associations and viral genetics to assess the possibility of further expansion and re-emergence of CHIKV illness.

Changing patterns of chikungunya virus: re-emergence of a zoonotic arbovirus

A chikungunya virus outbreak of unprecedented magnitude is currently ongoing in Indian Ocean territories. In Reunion Island, this alphavirus has already infected about one-third of the human population. The main clinical symptom of the disease is a painful and invalidating poly-arthralgia. Besides the arthralgic form, 123 patients with a confirmed chikungunya infection have developed severe clinical signs, i.e., neurological signs or fulminant hepatitis.

https://hal-pasteur.archives-ouvertes.fr/pasteur-01659363/document

Genome Microevolution of Chikungunya Viruses Causing the Indian Ocean Outbreak

Leptospirosis is one of the most widespread zoonoses in the world. However, there is a lack of information on circulating Leptospira strains in remote parts of the world. We describe the serological and molecular features of leptospires isolated from 94 leptospirosis patients in Mayotte, a French department located in the Comoros archipelago, between 2007 and 2010. Multilocus sequence typing identified these isolates as Leptospira interrogans, L. kirschneri, L. borgpetersenii, and members of a previously undefined phylogenetic group. This group, consisting of 15 strains, could represent a novel species. Serological typing revealed that 70% of the isolates belonged to the serogroup complex Mini/Sejroe/Hebdomadis, followed by the serogroups Pyrogenes, Grippotyphosa, and Pomona. However, unambiguous typing at the serovar level was not possible for most of the strains because the isolate could belong to more than one serovar or because serovar and species did not match the original classification. Our results indicate that the serovar and genotype distribution in Mayotte differs from what is observed in other regions, thus suggesting a high degree of diversity of circulating isolates worldwide. These results are essential for the improvement of current diagnostic tools and provide a starting point for a better understanding of the epidemiology of leptospirosis in this area of endemicity.

Human Leptospira Isolates Circulating in Mayotte (Indian Ocean) Have Unique Serological and Molecular Features

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.

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François Pettinelli

Papers

Genome Microevolution of Chikungunya Viruses Causing the Indian Ocean Outbreak

Human Leptospira Isolates Circulating in Mayotte (Indian Ocean) Have Unique Serological and Molecular Features

Genome analysis of Rift Valley Fever virus, Mayotte

Serological and Molecular Features Mayotte (Indian Ocean) Have Unique Human Leptospira Isolates Circulating in