Chikungunya fever: a re-emerging viral infection

Chikungunya (CHIK) fever is a re-emerging viral disease characterized by abrupt onset of fever with severe arthralgia followed by constitutional symptoms and rash lasting for 1-7 days. The disease is almost self-limiting and rarely fatal. Chikungunya virus (CHIKV) is a RNA virus belonging to family Togaviridae, genus Alphavirus. Molecular characterization has demonstrated two distinct lineages of strains which cause epidemics in Africa and Asia. These geographical genotypes exhibit differences in the transmission cycles. In contrast to Africa where sylvatic cycle is maintained between monkeys and wild mosquitoes, in Asia the cycle continues between humans and the Aedes aegypti mosquito. CHIKV is known to cause epidemics after a period of quiescence. The first recorded epidemic occurred in Tanzania in 1952-1953. In Asia, CHIK activity was documented since its isolation in Bangkok, Thailand in 1958. Virus transmission continued till 1964. After hiatus, the virus activity re-appeared in the mid-1970s and declined by 1976. In India, well-documented outbreaks occurred in 1963 and 1964 in Kolkata and southern India, respectively. Thereafter, a small outbreak of CHIK was reported from Sholapur district, Maharashtra in 1973. CHIKV emerged in the islands of South West Indian Ocean viz. French island of La Reunion, Mayotee, Mauritius and Seychelles which are reporting the outbreak since February, 2005. After quiescence of about three decades, CHIKV re-emerged in India in the states of Andhra Pradesh, Karnataka, Maharashtra, Madhya Pradesh and Tamil Nadu since December, 2005. Cases have also been reported from Rajasthan, Gujarat and Kerala. The outbreak is still continuing. National Institute of Communicable Diseases has conducted epidemiological, entomological and laboratory investigations for confirmation of the outbreak. These have been discussed in detail along with the major challenges that the country faced during the current outbreak.     

Comparative full genome analysis revealed E1: A226V shift in 2007 Indian Chikungunya virus isolates

The resurgence of Chikungunya virus (CHIKV) in the form of unprecedented explosive epidemic after a gap of 32 years in India is a point of major public health concern. In 2007 again there was outbreak in Kerala, India, affecting more than 25,000 cases with many reported mortalities. To understand the molecular basis of this high virulence and its implication in large-scale epidemic, a detailed systematic serological, virological and molecular investigation was undertaken with the epidemic samples of Kerala-2007. The comparative analysis of full genome sequence of Chikungunya virus isolate of 2007 with 2006 revealed three unique substitutions in structural and non-structural genes of 2007 isolate [two in E1 region (V14A and A226V) and one in Nsp1 (M184T)]. Our finding further substantiates the association of A226V shift in E1 gene with evolutionary success possibly due to adaptation in the mosquito vector with progression of epidemic, as observed in Reunion Island. This A226V shift which was absent in all 2006 Indian isolates, is found to be present in the four 2007 isolates, analysed in this study. These unique molecular features of the 2007 isolates with the progression of the epidemic from 2005 to 2007 demonstrate their high evolutionary and epidemic potential and thereby suggesting possible implication in higher magnitude and virulence of this outbreak.     

L’épidémie de grippe à virus A(H1N1) 2009 à la Réunion: données épidémiologiques

In Reunion Island, a French subtropical island located in the southern hemisphere, the monitoring of the epidemiological dynamics of the epidemic linked to the emergence of pandemic virus A(H1N1) 2009 was achieved through the regular influenza surveillance system which has been reinforced on that occasion. It was mainly based on a network of sentinel physicians, combined with virologic monitoring, and on surveillance of severe cases and deaths. The data were analyzed and retroinformation was distributed according to a weekly frequency. The first imported case was confirmed on July 5, 2009 in a traveler arriving from Australia, whereas the first autochthonous cases were reported on July 23. The epidemic peak was reached in five weeks and the duration of the whole epidemic episode was 9 weeks. Pandemic virus has quickly supplanted seasonal viruses that had begun to circulate. The estimated attack rate for symptomatic cases of infection with virus influenza A(H1N1) 2009 was 12.85%. The hospitalization rate was 32 per 10,000 estimated cases, and 24 people had a serious form requiring care in ICU. Among death certificates received at the regional office for health and social affairs, 14 mentioned the influenza, including 7 in whom the pandemic virus has been laboratory confirmed. These deaths occurred in patients significantly younger than usually observed in Reunion Island during the seasonal influenza epidemics. Overall, the epidemic intensity and severity have been similar to those of seasonal influenza in Reunion Island.     

Emerging and re-emerging viruses: A global challenge illustrated by Chikungunya virus outbreaks

In recent decades, the issue of emerging and re-emerging infectious diseases, especially those related to viruses, has become an increasingly important area of concern in public health. It is of significance to anticipate future epidemics by accumulating knowledge through appropriate research and by monitoring their emergence using indicators from different sources. The objective is to alert and respond effectively in order to reduce the adverse impact on the general populations. Most of the emerging pathogens in humans originate from known zoonosis. These pathogens have been engaged in long-standing and highly successful interactions with their hosts since their origins are exquisitely adapted to host parasitism. They developed strategies aimed at: (1) maximizing invasion rate; (2) selecting host traits that can reduce their impact on host life span and fertility; (3) ensuring timely replication and survival both within host and between hosts; and (4) facilitating reliable transmission to progeny. In this context, Arboviruses (or ARthropod-BOrne viruses), will represent with certainty a threat for the coming century. The unprecedented epidemic of Chikungunya virus which occurred between 2005 and 2006 in the French Reunion Island in the Indian Ocean, followed by several outbreaks in other parts of the world, such as India and Southern Europe, has attracted the attention of medical and state authorities about the risks linked to this re-emerging mosquito-borne virus. This is an excellent model to illustrate the issues we are facing today and to improve how to respond tomorrow.     

No evidence of chikungunya virus and antibodies shortly before the outbreak on Sri Lanka

A massive outbreak of chikungunya disease occurred on Sri Lanka in 2006. Reasons for the explosive nature of the epidemic are being intensively discussed. According to recognised and anecdotal concepts, absence of human population immunity against chikungunya virus (CHIKV) might have supported virus amplification. However, formal proof of concept is lacking. This study determined the prevalence of anti-CHIKV IgG antibodies as well as CHIKV RNA shortly before the outbreak. Two hundred and six human sera were collected from patients with acute febrile illness in 2004/2005. Validated indirect immunofluorescence and real-time RT-PCR assays for dengue as well as CHIKV were employed. Laboratory evidence of dengue virus infection was seen in 67% of patients, indicating virus activity and exposure to Aedes spp. vectors. These vectors are the same as for chikungunya. However, no evidence of acute or previous chikungunya infection could be demonstrated in the same cohort. This study gives formal evidence that the absence of human population immunity correlated with a large chikungunya epidemic. M. Panning and D. Wichmann contributed equally to this work.     

Application of real-time RT-PCR in vector surveillance and assessment of replication kinetics of an emerging novel ECSA genotype of Chikungunya virus in Aedes aegypti

Chikungunya has emerged as one of the most important arboviral infection of global significance. Expansion of Chikungunya virus endemic areas can be ascribed to naive population, increasing vector population and adaptability of virus to new vector. In this study, a SYBR Green I based quantitative RT-PCR assay was developed. The assay was found to be 10-fold more sensitive than conventional RT-PCR and no cross reactivity was observed with related alphaviruses and flaviviruses. The detection efficiency of the assay was impervious to mosquitoes of different pool sizes. Vector surveillance has resulted in detection of CHIKV RNA in Aedes aegypti, confirming its vectorial potential for CHIKV in northern India. The assessment of the assay was further carried out by studying the competence of Indian Ae. aegypti for CHIKV, which revealed 100% infection rate and dissemination rate with 60% transmission rate. The replication kinetics of CHIKV in different anatomical sites of Ae. aegypti revealed highest titre at day 6 post infection in midgut and at day 10 post infection in saliva, legs and wings. The implementation of the assay in detecting lower viral load makes it a remarkable tool for surveillance of virus activity in mosquitoes.     

Prevalence of hepatitis A, B, C virus markers in Réunion (south hospital and Saint Pierre prison)

We studied the prevalence of Hepatitis A, B, C in different groups in the population of the South of Reunion Island. The aims of this study were the following: to estimate the prevalence of Hepatitis C virus (HCV) (anti-HCV antibodies) and Hepatitis B virus (HBV) (anti-HBc, HBs Ag and anti-HBs) in a population of 1455 women, who delivered in the Centre hospitalier Sud Reunion (CHSR), to estimate the prevalence of these two viruses in a population selected for risk factors (100 prisoners), to estimate the prevalence of Hepatitis A in a group of 400 persons (aged 0 to 19) hospitalised in CHSR since 1st January 1998 (100 for each 5-year age bracket), to research risks factors in these populations and immunity. The overall prevalence of anti-HCV was 0.14% in pregnant women and risk factor associated was found in 28.9% of this population (2.9% history of transfusion, 0.21% drug users). In the group of prisoners seroprevalence was 2%, far below that of prisoners in France. Anti-HCV seroprevalence is weak in Reunion Island and very inferior to seroprevalence in the French population as in other Indian Ocean islands. This is due to the low risk of parenteral transmission. Anti-HBc was found in 90 serum samples from women (overall prevalence 6.35%) and of these 90 positive samples, 9 were positive for HBs Ag (overall prevalence 0.63%), 68 were positive for anti-HBs (4.81%) and 22 (1.54%) were anti-HBc isolated (without HBs Ag and anti-HBs). The overall prevalence of anti-HBs was 62.8%. In the population of 100 prisoners, 2 were HBs Ag positive, 10 anti-HBc positive (2 anti-HBc isolated, 2 associated with HBs Ag, 6 with anti-HBs). The prevalence of anti-HBs was 22%. The major risk factor observed in this population of prisoners was tattooing and/or piercing (46%). These results show that: Reunion island is an area of low endemicity for HBV virus. The measure of protective inoculation is well followed. i.v. drug abuse and previous transfusion are weak routes of transmission. In the group aged 0 to 19, overall prevalence of anti-HAV was 11.9% with the highest rate found among 15 to 19 year-olds (25%). Seroprevalence falls with socio-economic progress. At the present time, the endemic is intermediate in Reunion Island. Given immunity levels within the young population, there is a risk of outbreak. This risk is due to the conditions in Reunion Island, but also to people who travel to other Indian Ocean countries where endemicity is high. It is thus very important that a vaccination strategy be determined.     

A review of the dynamics and severity of the pandemic A(H1N1) influenza virus on Réunion Island, 2009

On Reunion Island, in response to the threat of emergence of the pandemic influenza A(H1N1)2009 virus, we implemented enhanced influenza surveillance from May 2009 onwards in order to detect the introduction of pandemic H1N1 influenza and to monitor its spread and impact on public health. The first 2009 pandemic influenza A(H1N1) virus was identified in Réunion on July 5, 2009, in a traveller returning from Australia; seasonal influenza B virus activity had already been detected. By the end of July, a sustained community pandemic virus transmission had been established. Pandemic H1N1 influenza activity peaked during week 35 (24–30 August 2009), 4 weeks after the beginning of the epidemic. The epidemic ended on week 38 and had lasted 9 weeks. During these 9 weeks, an estimated 66 915 persons who consulted a physician could have been infected by the influenza A(H1N1)2009 virus, giving a cumulative attack rate for consultants of 8.26%. Taking into account the people who did not consult, the total number of infected persons reached 104 067, giving a cumulative attack rate for symptomatics of 12.85%. The crude fatality rate (CFR) for influenza A(H1N1)2009 and the CFR for acute respiratory infection was 0.7/10 000 cases. Our data show that influenza pandemic did not have a health impact on overall mortality on Réunion Island. These findings demonstrate the value of an integrated epidemiological, virological and hospital surveillance programme to monitor the scope of an epidemic, identify circulating strains and provide some guidance to public health control measures.     

Factors associated with persistence of arthralgia among chikungunya virus-infected travellers: Report of 42 French cases

BackgroundIn 2005–2006, a major epidemic of CHIKV infection occurred in the Islands of the south-western Indian Ocean, and longstanding manifestations seemed to be more frequent than described before.ObjectivesTo describe the frequency and related factors of late clinical manifestations of CHIKV infection among imported cases living in Aquitaine area, France.Study designAll patients recruited through the travel clinic and tropical medicine unit of the University Hospital Centre of Bordeaux with possible CHIKV infection were prospectively recorded, and confirmed cases of CHIKV infection were interviewed 2 years after infection. Factors associated with the persistence of symptoms were determined by multivariate logistic regression.ResultsAmong the 29 cases followed, 17 still suffered from arthralgia 2 years after infection, and most of them had never recovered from the initial phase of the condition. The risk of persistent arthralgia tended to be higher among subjects with low educational level, subjects infected in the Reunion Island, and when initial phase lasted 30 days or more and was characterised by a severe pain.ConclusionsConsistent with previous studies, our findings showed worsened late manifestations among patients returning from Indian Ocean area. Persistence of symptoms tended to be linked with clinical burden during the acute phase, which can be informative for early recognition and management of patients at risk for developing persistent rheumatic symptoms. Cryoglobulins failed to be identified in seronegative patients with invalidating dengue-like syndrome.     

Gestion des alertes arbovirales : retour d’expérience du groupe de travail Secproch du Haut Conseil de la santé publique (2019–2021)

The Secproch working group (for “sécurité des produits issus du corps humain”) was created in 2019 within the « Haut Conseil de la santé publique » (HCSP) for addressing all the questions related to labile blood products, organs, tissues, cells (OTC) and gametes issued from human body. It is notably in charge of the management of alerts regarding arbovirus infections. These infections due to arthropod-transmitted viruses are responsible for emergence and reemergence, notably in the context of global warming. This review relates the alerts taken into consideration by the Secproch group between 2019 and 2021 following three pathologies due to Flaviviridae : dengue, West Nile virus (WNV) infection and tick-borne encephalitis (TBE). The dengue alerts have occurred in French Indies where the virus is endemic/epidemic, Reunion Island where the population was naïve until 2018 towards the virus, and the metropole where foci of autochthonous cases are observed sporadically. The WNV infection was responsible of both human and equine cases in 2019 in the South of France but with intensity much less than in 2018. At last, the TBE virus was at the origin of a cluster of about 40 cases in the Ain department following a contamination by crude non-pasteurized goat cheese. This review offers the opportunity to reevaluate the risks linked to these three viruses through blood products and organs/tissues/cells and to precise the means recommended by HCSP to secure these products.     

Evaluation of the first commercial chikungunya virus indirect immunofluorescence test

The chikungunya virus (CHIKV), an arbovirus of the genus Alphavirus, family Togaviridae, is mainly transmitted by Aedes mosquitoes. It causes an acute infection, characterized by high fever, polyarthralgia and rash and was responsible for a major outbreak which started in 2005 and spread over many islands of the south western Indian Ocean before it hit the Indian subcontinent. As nucleic acid amplification can be used only during the viremic period, serological tests are most widely used for the diagnosis of CHIKV infections. CHIKV IgM and IgG antibodies can be detected as soon as 3-6 days after clinical onset, respectively. Presently only in-house ELISA and immunofluorescence tests exist for analysing the CHIKV specific immune response. The first commercial indirect immunofluorescence test (IIFT) (EUROIMMUN AG, Lüebeck, Germany) was evaluated using two sera panels of patients from La Reunion and travellers returning with CHIKV infections from the Indian Ocean region. The IgM IIFT shows a specificity of 98.3% and a sensitivity of 96.9%. The specificity and sensitivity for the IgG IIFT are 100.0% and 95.4%, respectively. This commercial IIFT is a valuable tool for the diagnosis of CHIKV infections and antibody seroprevalence studies.     

Genetic diversity of Chikungunya virus, India 2006-2010: evolutionary dynamics and serotype analyses

The genetic diversity of Chikungunya virus (CHIKV) causing recurring outbreaks in India since 2006 was studied. The 2006 epidemic was caused by a virus strain of the East, Central and South African (ECSA) genotype with 226A in the E1 glycoprotein. The variant strain with E1-A226V mutation caused outbreaks since 2007 in the state of Kerala where Aedes albopictus is the abundant mosquito vector. Molecular epidemiology data since 2007 is scarce from other regions of the country. RT-PCR, sequencing and phylogenetic analyses of CHIKV isolates from the 2009 to 2010 epidemics in the States of Tamil Nadu and Andhra Pradesh placed them in a separate clade within the ECSA lineage. The isolates of the study had 226A in the E1 glycoprotein. The isolates had a novel E1-K211E mutation that was under significant positive selection. E1-211E is highly conserved in the Asian genotype of the virus circulated by Aedes aegypti. Unique mutations in E2 glycoprotein were identified. The two sub-lineages of ECSA genotype circulating in India parallel the abundance of Ae. albopictus and Ae. aegypti. Novel mutations in the envelope glycoproteins suggest adaptive evolution of the virus to local vector abundance. Cross neutralization of the virus isolates from recurring Indian epidemics indicated that no distinct serotypes had evolved. The study has provided insights into the origin, distribution and evolutionary adaptation of the virus to local vector abundance in the region that has reportedly, the highest incidence of CHIKV infection in the world.     

The biology of chikungunya: a brief review of what we still do not know

Responsible for a massive outbreak in the Indian Ocean in 2005-2006, the chikungunya virus is also reemerging in India where it has already infected over a million persons. Imported cases of the disease are reported in Asia, USA, and Europe, where a small epidemic occurred, due to transmission by local mosquitoes. Chikungunya virus is an alphavirus (Togaviridae family) that usually induces an acute illness characterized by fever, rash, and painful, incapacitating arthralgia a few days after being bitten by an infected mosquito, but recurrent joint pains are frequent. Unusual severe forms of the disease are also being reported that emphasize the importance of close monitoring of arboviruses in more fragile populations, such as the elderly and the newborns. Alphaviruses have generally been studied out of their epidemic context, leading to a large knowledge of their molecular features, and a much narrower understanding of their epidemiology and induced pathogenesis. Deciphering chikungunya virus specific molecular features as well as how the virus interacts with its vector and with its host are key to foresee, prevent and manage future epidemics, as well as prevent, treat or cure chikungunya disease.     

Le concept de maladies virales émergentes : quel risque de zoonose pour La Réunion ?

In Reunion Island, the risk of emerging infectious diseases lies mainly in several viral zoonoses: West Nile fever, Sindbis virus, Nipah virus, Wesselsbron virus, Rift Valley fever and Japanese encephalitis. There morbidity and consequences are more or less important but they all have a non-negligible epidemic potential, so they have to be monitored. Indeed, the struggle against these emerging infectious diseases requires an early detection of the cases, thus a surveillance system capable of detecting them as early as possible, thanks to a real international network of information, warning and prevention.     

Global protein profiling studies of chikungunya virus infection identify different proteins but common biological processes

Chikungunya fever (CHIKF) caused by the mosquito‐transmitted chikungunya virus (CHIKV) swept into international prominence from late 2005 as an epidemic of CHIKF spread around countries surrounding the Indian Ocean. Although significant advances have been made in understanding the pathobiology of CHIKF, numerous questions still remain. In the absence of commercially available specific drugs to treat the disease, or a vaccine to prevent the diseases, the questions have particular significance. A number of studies have used global proteome analysis to increase our understanding of the process of CHIKV infection using a number of different experimental techniques and experimental systems. In all, over 700 proteins have been identified in nine different analyses by five different groups as being differentially regulated. Remarkably, only a single protein, eukaryotic elongation factor 2, has been identified by more than two different groups as being differentially regulated during CHIKV infection. This review provides a critical overview of the studies that have used global protein profiling to understand CHIKV infection and shows that while a broad consensus is emerging on which biological processes are altered during CHIKV infection, this consensus is poorly supported in terms of consistent identification of any key proteins mediating those biological processes. Copyright © 2014 John Wiley & Sons, Ltd.     

Human Venezuelan equine encephalitis virus infection and diabetes in Zulia State, Venezuela

Venezuelan equine encephalitis (VEE) virus has been implicated as producing alterations in glucose metabolism in animals. We performed oral glucose tolerance tests and measured serum immunoreactive insulin responses in 13 patients who were infected by VEE virus during an epidemic in 1969, in Zulia State, Venezuela. No significant alterations in the glucose tolerance test were found. Sera of 86 diabetic outpatients and 98 control individuals with normal glycemia at a local hospital were tested for antibodies to VEE virus by hemagglutination inhibition. No statistically significant difference was found between the two groups; 10.4% of the diabetic patients had detectable antibodies against VEE virus, compared to 7.1% of controls. Seventy-three percent of the diabetics with antibodies were individuals over 40 yr old, whose diabetes could be catalogued as insulin independent. The results of these studies indicate no relationship of VEE virus infection to subsequent diabetes.     

Persistent of respiratory syncytial virus in human dendritic cells and influence of nitric oxide

The annual epidemics of respiratory syncytial virus (RSV) infection are probably explained by poor herd immunity and the existence of a dormant reservoir of virus that is activated by an unknown trigger. The virus causes particular problems in infants, the elderly and patients with chronic obstructive airways disease (COPD). During two consecutive winters, human monocyte-derived dendritic cells (DCs) were exposed on a single occasion to one of two forms of RSV labelled with a fluorescent expresser genes (rgRSV or rrRSV) during the epidemic season. The cultures were maintained for many months, with fresh DCs being added at monthly intervals. The cultures were variously exposed to 600 parts per billion (ppb) nitric oxide for 15 min, nitric oxide (NO) donors and NO inhibitors outside the RSV epidemic season. The pattern of productive infection of DCs in vitro appeared to parallel the natural epidemics, in that DCs exhibited evidence of viral replication and productive infection only as manifested by intracellular fluorescence and infection of HeLa cells during the RSV epidemic season. When the long-term cultures were exposed to the above agents outside the RSV epidemic season there was again evidence of vigorous replication and productive infection, as shown by the reappearance of fluorescence and productive infection of HeLa cells. The results indicate that RSV may remain dormant in dendritic cells for prolonged periods and that replication appears to be activated by suppression of endogenous NO production. These observations may be key to our understanding of the mechanisms contributing to the annual epidemics of RSV infection.