Circulation of Chikungunya virus in Gabon, 2006-2007

This study reports the first isolation and partial genetic characterization of Chikungunya virus (CHIKV) from patients during a 2006-2007 dengue-like syndrome outbreak in Gabon. The isolated viruses were phylogenetically close to strains isolated in the Democratic Republic of the Congo 7 years ago and to strains isolated more recently in Cameroon. These results indicate a continuing circulation of a genetically stable CHIKV population during 7 years in Central Africa.     

Dengue virus and other arboviruses: a global view of risks

Arboviruses (arthropod-borne viruses) are an ecological group of viruses from different families (e.g. Bunyaviridae, Flaviviridae and Togaviridae) that use arthropods such as mosquitoes, flies and ticks as vectors for transmission between different hosts. The superb plasticity of these viruses allows propagation to different host systems including both invertebrates and vertebrates. More than 500 species of arbo-virus have been described and are listed in the International Catalogue of arbo-virus ( http://www.cdc.gov/nczved/divisions/dvbid/arbovirus.html ), many of which are of medical importance. Globally, arboviral infections have become increasingly common and human diseases caused by these infections have expanded their frontiers in the last few decades emerging in places with no previous history of epidemic activity or localised transmission of a specific arbovirus. One example is the recent arrival of West Nile virus (WNV) in the Western Hemisphere and its subsequent propagation in the Americas. Arboviral diseases are also re-emerging in places where the disease had previously been well-controlled or eradicated, resulting in an increasing number of cases and more severe forms of disease in endemic regions. Human infections with arboviruses are mostly asymptomatic, but symptomatic infections can range from malaise, mild febrile illness (with flu-like symptoms) to severe disease that may progress to long-term physical or cognitive impairment and/or mortality. Arboviral infections have an incubation period during which viral replication with a viremic phase takes place in the absence of symptoms. Viremic blood has the potential to transmit infection to blood recipients and therefore arboviruses can pose a threat to the safety of the blood supply. For instance, during an epidemic, asymptomatic individuals may donate blood and transmit the infection to blood component recipients. Among the arboviral infections that have been on the radar for increased activity in the last decade are: WNV, Dengue viruses (DENV) and Chikungunya virus (CHIKV). In addition, other arboviral infections such as Yellow Fever, Saint Louis encephalitis, Tick-borne encephalitis, Rift Valley fever, Japanese encephalitis, Powassan encephalitis, Murray Valley encephalitis and Zika fever have been reported as emerging or re-emerging in various areas around the globe. Alertness and surveillance are required to allow implementation of measures to mitigate risk of transmission to blood recipients including blood screening tests when available and appropriate. In addition, the evidence of increased arbovirus activity worldwide points to the critical need for the development of affordable diagnostic and screening assays with high sensitivity and specificity as well as new vaccines and therapies, since most populations at risk reside in less privileged parts of the world. The need for these tools is pressed by the imminent possibility of outbreaks in any part of the world due to the combination of expanding distribution of vectors and increased mobility of infected hosts by travel and trade.     

3种重要虫媒病毒的RT-PCR检测

目的：建立快速、敏感、特异的虫媒病毒RT-PCR检测方法。方法：采用改进的核酸制备方法，分别从感染的乳鼠脑和细胞培养上清液中提取病毒RNA，再用RT-PCR和套式PCR方法进行检测。结果：通过对肌PCR反应条件的优化，用3种虫媒病毒的特异引物均可从不同稀释度的感染小鼠脑和细胞上清中提取的病毒RNA扩增出特异的目的基因片段。甲病毒属的东部马脑炎病毒和西部马脑炎病毒之间，及与黄病毒属的黄热病毒均无交叉反应，表明建立的RT-PCR检测方法特异性强。套式PCR与肝PCR比较可提高检测敏感性10～10000倍。结论：建立的肝PCR和套式：PCR法可用于3种虫媒病毒的快速检测。     

Sloths host Anhanga virus‐related phleboviruses across large distances in time and space

Sloths are genetically and physiologically divergent mammals. Phleboviruses are major arthropod‐borne viruses (arboviruses) causing disease in humans and other animals globally. Sloths host arboviruses, but virus detections are scarce. A phlebovirus termed Anhanga virus (ANHV) was isolated from a Brazilian Linnaeus's two‐toed sloth (Choloepus didactylus) in 1962. Here, we investigated the presence of phleboviruses in sera sampled in 2014 from 74 Hoffmann's two‐toed (Choloepus hoffmanni, n = 65) and three‐toed (Bradypus variegatus, n = 9) sloths in Costa Rica by broadly reactive RT‐PCR. A clinically healthy adult Hoffmann's two‐toed sloth was infected with a phlebovirus. Viral load in this animal was high at 8.5 × 10⁷ RNA copies/ml. The full coding sequence of the virus was determined by deep sequencing. Phylogenetic analyses and sequence distance comparisons revealed that the new sloth virus, likely representing a new phlebovirus species, provisionally named Penshurt virus (PEHV), was most closely related to ANHV, with amino acid identities of 93.1%, 84.6%, 94.7% and 89.0% in the translated L, M, N and NSs genes, respectively. Significantly more non‐synonymous mutations relative to ANHV occurred in the M gene encoding the viral glycoproteins and in the NSs gene encoding a putative interferon antagonist compared to L and N genes. This was compatible with viral adaptation to different sloth species and with micro‐evolutionary processes associated with immune evasion during the genealogy of sloth‐associated phleboviruses. However, gene‐wide mean dN/dS ratios were low at 0.02–0.15 and no sites showed significant evidence for positive selection, pointing to comparable selection pressures within sloth‐associated viruses and genetically related phleboviruses infecting hosts other than sloths. The detection of a new phlebovirus closely‐related to ANHV, in sloths from Costa Rica fifty years after and more than 3,000 km away from the isolation of ANHV confirmed the host associations of ANHV‐related phleboviruses with the two extant species of two‐toed sloths.     

Concurrent Chikungunya and Dengue Virus Infections during Simultaneous Outbreaks, Gabon, 2007

An outbreak of febrile illness occurred in Gabon in 2007, with 20,000 suspected cases. Chikungunya or dengue-2 virus infections were identified in 321 patients; 8 patients had documented co-infections. Aedes albopictus was identified as the principal vector for the transmission of both viruses.     

Ross River virus disease reemergence, Fiji, 2003-2004

We report 2 clinically characteristic and serologically positive cases of Ross River virus infection in Canadian tourists who visited Fiji in late 2003 and early 2004. This report suggests that Ross River virus is once again circulating in Fiji, where it apparently disappeared after causing an epidemic in 1979 to 1980.