A Report of Zika Virus Seroprevalence in Republic of the Congo.

Zika virus (ZIKV) is an arthropod-borne RNA virus (arbovirus), belonging to the Spondweni serogroup. ZIKV was first described in Africa in 1947 and remained sporadic until Micronesia outbreak in 2007, which was followed by outbreaks in the Pacific Islands, Latin America, and the Caribbean. Subsequent to the epidemics, ZIKV revealed its severity as virus was sexually transmissible, and it was associated with serious fetal and neurological complications. ZIKV originated from Africa; however, little is known about the epidemiology of the virus in African populations. Following a recent study in Cameroon that evidenced low ZIKV epidemiology associated with a presumptive (peri-)sylvatic transmission, we performed a seroepidemiological study in Republic of the Congo, neighbor of Cameroon. To accomplish this, 386 serum specimens from volunteer blood donors collected in 2011 from rural and urban areas of Republic of the Congo were tested with ZIKV-specific methodology; primary screening with anti-NS1 ZIKV IgG ELISA followed by confirmation with cytopathic effect (CPE)-based virus neutralization test (VNT). ZIKV seropositivity was determined as low as 1.8%, varying slightly between urban and rural areas (1.7% and 3.6%). These results demonstrate that the majority of the population of Republic of the Congo is immunologically naïve against ZIKV with a presumptive (peri-)sylvatic transmission cycle, which emphasizes the importance of surveillance studies in Africa.

Risk Factors Associated with Ebola and Marburg Viruses Seroprevalence in Blood Donors in the Republic of Congo.

BACKGROUND: Ebola and Marburg viruses (family Filoviridae, genera Ebolavirus and Marburgvirus) cause haemorrhagic fevers in humans, often associated with high mortality rates. The presence of antibodies to Ebola virus (EBOV) and Marburg virus (MARV) has been reported in some African countries in individuals without a history of haemorrhagic fever. In this study, we present a MARV and EBOV seroprevalence study conducted amongst blood donors in the Republic of Congo and the analysis of risk factors for contact with EBOV. METHODOLOGY AND FINDINGS: In 2011, we conducted a MARV and EBOV seroprevalence study amongst 809 blood donors recruited in rural (75; 9.3%) and urban (734; 90.7%) areas of the Republic of Congo. Serum titres of IgG antibodies to MARV and EBOV were assessed by indirect double-immunofluorescence microscopy. MARV seroprevalence was 0.5% (4 in 809) without any identified risk factors. Prevalence of IgG to EBOV was 2.5%, peaking at 4% in rural areas and in Pointe Noire. Independent risk factors identified by multivariate analysis were contact with bats and exposure to birds. CONCLUSIONS/SIGNIFICANCE: This MARV and EBOV serological survey performed in the Republic of Congo identifies a probable role for environmental determinants of exposure to EBOV. It highlights the requirement for extending our understanding of the ecological and epidemiological risk of bats (previously identified as a potential ecological reservoir) and birds as vectors of EBOV to humans, and characterising the protection potentially afforded by EBOV-specific antibodies as detected in blood donors.

First reported chikungunya fever outbreak in the republic of Congo, 2011.

BACKGROUND: Chikungunya is an Aedes -borne disease characterised by febrile arthralgia and responsible for massive outbreaks. We present a prospective clinical cohort study and a retrospective serological study relating to a CHIK outbreak, in the Republic of Congo in 2011. METHODOLOGY AND FINDINGS: We analysed 317 suspected cases, of which 308 (97.2%) lived in the city of Brazzaville (66.6% in the South area). Amongst them, 37 (11.7%) were CHIKV+ve patients (i.e., biologically confirmed by a real-time RT-PCR assay), of whom 36 (97.3%) had fever, 22 (66.7%) myalgia and 32 (86.5%) arthralgia. All tested negative for dengue. The distribution of incident cases within Brazzaville districts was compared with CHIKV seroprevalence before the outbreak (34.4% in 517 blood donors), providing evidence for previous circulation of CHIKV. We applied a CHIK clinical score to 126 patients recruited within the two first day of illness (including 28 CHIKV+ves (22.2%)) with sensitivity (78.6%) and specificity (72.4%) values comparing with those of the referent study in Reunion Island. The negative predictive value was high (92%), but the positive predictive value (45%) indicate poor potential contribution to medical practice to identify CHIKV+ve patients in low prevalence outbreaks. However, the score allowed a slightly more accurate follow-up of the evolution of the outbreak than the criterion "fever+arthralgia". The complete sequencing of a Congolase isolate (Brazza_MRS1) demonstrated belonging to the East/Central/South African lineage and was further used for producing a robust genome-scale CHIKV phylogenetic analysis. CONCLUSIONS/SIGNIFICANCE: We describe the first Chikungunya outbreak declared in the Republic of Congo. The seroprevalence study conducted amongst blood donors before outbreak provided evidence for previous CHIKV circulation. We suggest that a more systematic survey of the entomological situation and of arbovirus circulation is necessary in Central Africa for better understanding the environmental, microbiological and sociological determinants of emergence.

Chikungunya fever: epidemiology, clinical syndrome, pathogenesis and therapy.

Chikungunya virus (CHIKV) is the aetiological agent of the mosquito-borne disease chikungunya fever, a debilitating arthritic disease that, during the past 7years, has caused immeasurable morbidity and some mortality in humans, including newborn babies, following its emergence and dispersal out of Africa to the Indian Ocean islands and Asia. Since the first reports of its existence in Africa in the 1950s, more than 1500 scientific publications on the different aspects of the disease and its causative agent have been produced. Analysis of these publications shows that, following a number of studies in the 1960s and 1970s, and in the absence of autochthonous cases in developed countries, the interest of the scientific community remained low. However, in 2005 chikungunya fever unexpectedly re-emerged in the form of devastating epidemics in and around the Indian Ocean. These outbreaks were associated with mutations in the viral genome that facilitated the replication of the virus in Aedes albopictus mosquitoes. Since then, nearly 1000 publications on chikungunya fever have been referenced in the PubMed database. This article provides a comprehensive review of chikungunya fever and CHIKV, including clinical data, epidemiological reports, therapeutic aspects and data relating to animal models for in vivo laboratory studies. It includes Supplementary Tables of all WHO outbreak bulletins, ProMED Mail alerts, viral sequences available on GenBank, and PubMed reports of clinical cases and seroprevalence studies.

Factors associated with post-seasonal serological titer and risk factors for infection with the pandemic A/H1N1 virus in the French general population.

The CoPanFlu-France cohort of households was set up in 2009 to study the risk factors for infection by the pandemic influenza virus (H1N1pdm) in the French general population. The authors developed an integrative data-driven approach to identify individual, collective and environmental factors associated with the post-seasonal serological H1N1pdm geometric mean titer, and derived a nested case-control analysis to identify risk factors for infection during the first season. This analysis included 1377 subjects (601 households). The GMT for the general population was 47.1 (95% confidence interval (CI): 45.1, 49.2). According to a multivariable analysis, pandemic vaccination, seasonal vaccination in 2009, recent history of influenza-like illness, asthma, chronic obstructive pulmonary disease, social contacts at school and use of public transports by the local population were associated with a higher GMT, whereas history of smoking was associated with a lower GMT. Additionally, young age at inclusion and risk perception of exposure to the virus at work were identified as possible risk factors, whereas presence of an air humidifier in the living room was a possible protective factor. These findings will be interpreted in light of the longitudinal analyses of this ongoing cohort.