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.

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

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.

Chikungunya virus infection is a rapid-onset, febrile disease with intense asthenia, arthralgia, myalgia, headache, and rash. This mosquito-borne alphavirus has spread throughout the Caribbean and into much of Central America. Further spread in the Americas seems likely.

https://www.nejm.org/doi/suppl/10.1056/NEJMra1406035/suppl_file/nejmra1406035_appendix.pdf

Chikungunya Virus and the Global Spread of a Mosquito-Borne Disease

Since October 2013, French Polynesia has experienced the largest documented outbreak of Zika virus (ZIKAV) infection. To prevent transmission of ZIKAV by blood transfusion, specific nucleic acid testing of blood donors was implemented. From November 2013 to February 2014: 42 (3%) of 1,505 blood donors, although asymptomatic at the time of blood donation, were found positive for ZIKAV by PCR. Our results serve to alert blood safety authorities about the risk of post-transfusion Zika fever.

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Potential for Zika virus transmission through blood transfusion demonstrated during an outbreak in French Polynesia, November 2013 to February 2014.

In January 2005, an epidemic of chikungunya fever broke out in the Comoro Islands and lasted until May 2005. In April, cases were also reported in Mayotte and Mauritius. On Reunion Island, the first cases were reported at the end of April. Surveillance of this epidemic required an adaptive system, which at first was based on active and retrospective case detection around the cases reported, then relied on a sentinel network when the incidence increased. Emerging and severe forms of infection were investigated. Death certificates were monitored. By April 2006, the surveillance estimate was 244,000 cases of chikungunya virus infection, including 123 severe cases and 41 of maternoneonatal transmission, with an overall attack rate of 35%. Chikungunya infection was mentioned on 203 death certificates and significant mortality was observed. This epidemic highlighted the need for a mutual strategy of providing information on arboviral diseases and their prevention and control between countries in the southwestern Indian Ocean.

A major epidemic of chikungunya virus infection on Reunion Island, France, 2005-2006.

In April 2005, an outbreak of Chikungunya fever occurred on the island of Reunion in the Indian Ocean During winter 2005, six patients developed meningoencephalitis and acute hepatitis due to Chikungunya virus Our objectives were to determine the incidence and mortality of atypical Chikungunya viral infections and to identify risk factors for severe disease A hospital-based surveillance system was established to collect data on atypical Chikungunya cases Case reports, medical records and laboratory results were reviewed and analysed We defined an atypical case as one in which a patient with laboratory-confirmed Chikungunya virus infection developed symptoms other than fever and arthralgia We defined a severe atypical case as one which required maintenance of at least one vital function We recorded 610 atypical cases of Chikungunya fever: 222 were severe cases, 65 affected patients died Five hundred and forty-six cases had underlying medical conditions (of which 226 suffered from cardiovascular, 147 from neurological and 150 from respiratory disorders) Clinical features that had never been associated with Chikungunya fever were recorded, such as bullous dermatosis, pneumonia, and diabetes mellitus Hypertension, and underlying respiratory or cardiological conditions were independent risk factors for disease severity The overall mortality rate was 106% and it increased with age This is the first time that severe cases and deaths due to Chikungunya fever have been documented The information presented in this article may assist clinicians in identifying the disease, selecting the treatment strategy, and anticipating the course of illness

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0950268808001167

Atypical Chikungunya virus infections: clinical manifestations, mortality and risk factors for severe disease during the 2005-2006 outbreak on Réunion.

Estimated risk of Chikungunya viremic blood donation during an epidemic on Reunion Island in the Indian Ocean, 2005 to 2007.

Chikungunya outbreak in Reunion: epidemiology and surveillance, 2005 to early January 2006.

By 9 April 2006, 241 000 cases of chikungunya had been reported on the island of Reunion, and 5339 cases on the island of Mayotte. The islands of Mauritius, Seychelles, Madagascar, and Comoros are also affected

I Quatresous

Papers

A major epidemic of chikungunya virus infection on Reunion Island, France, 2005-2006.

Atypical Chikungunya virus infections: clinical manifestations, mortality and risk factors for severe disease during the 2005-2006 outbreak on Réunion.

Estimated risk of Chikungunya viremic blood donation during an epidemic on Reunion Island in the Indian Ocean, 2005 to 2007.

Chikungunya outbreak in Reunion: epidemiology and surveillance, 2005 to early January 2006.

Imported cases of chikungunya in metropolitan France, April 2005 - February 2006.