[Analysis on molecular genetic evolution of Banna virus based on the 12th segment].

Objective: To understand the evolution characteristics of Banna viruses (BAVs) isolated worldwide from 1980 to 2012. Methods: In this study, a phylogenetic analysis using Bayesian Markov Chain Monte Carlo simulations was conducted on all available 12th segment of genes of BAVs isolated worldwide from 1980 to 2012 to investigate the evolutionary and epidemiologic dynamics of BAVs. Results: The Bayesian phylogenetic analysis of BAVs revealed that the common ancestor of BAVs appeared 315 (95%HPD: 63-619) years ago. The evolutionary rate of BAV based on the 12th segment gene was estimated to be 2.33×10-3 (95%HPD: 2.84× 10-4-8.52×10-3) substitution per site per year, indicating BAV belong to an emerging arbovirus with rapid evolution. Conclusion: The evolution of emerging BAVs is rapid and the distribution of BAVs has expanded with new variant being detected, so it is necessary to enhance the surveillance to fully understand the natural distribution and pathogenicity of BAVs.

Coltiviruses and seadornaviruses in North America, Europe, and Asia.

Coltiviruses are tickborne viruses of the genus Coltivirus. The type species, Colorado tick fever virus (from North America), has been isolated from patients with flulike syndromes, meningitis, encephalitis, and other severe complications. Another coltivirus, Eyach virus, has been isolated from ticks in France and Germany and incriminated in febrile illnesses and neurologic syndromes. Seadornaviruses are endemic in Southeast Asia, particularly Indonesia and China. The prototype virus of the genus, Banna virus (BAV), has been isolated from many mosquito species, humans with encephalitis, pigs, and cattle. Two other seadornaviruses, Kadipiro and Liao Ning, were isolated only from mosquitoes. The epidemiology of seadornaviruses remains poorly documented. Evidence suggests that BAV is responsible for encephalitis in humans. Infection with BAV may be underreported because it circulates in regions with a high incidence of Japanese encephalitis and could be misdiagnosed as this disease.

[Erve and Eyach: two viruses isolated in France, neuropathogenic for man and widely distributed in Western Europe]. / Erve et Eyach: deux virus isolés en France, neuropathogènes chez l'homme et à diffusion ouest-européenne.

Two arboviruses have been isolated from Mayenne, western France, in 1981-1982, during systematic field surveys: Eyach virus, a cultivirus from Ixodes ricinus and I. ventalloi ticks, and Erve virus, a nairovirus from the tissues of white-toothed shrews, Crocidura russula. For many years, these two viruses were considered as "orphan viruses" without pathogenic power for man, since it became evident that they circulate actively in Europe among populations of wild small and large mammals. Moreover, these viruses are able to infect human beings and were responsible for severe neurological disorders. The presently known geographical distribution of these agents includes France, Germany, Netherlands and Czech Republic.

[Isolation of coltivirus from mosquitoes in Beijing and it's biological characteristics].

Two strains (Beijing 95-70 and 95-75) of coltivirus were isolated from mosquitoes collected in Beijing during summer-autumn in 1994. The viruses caused cytopathogenic effect on C6/36 cells but not on BHK-21 and Vero cells, and were not lethal for new born mice and three week old mice. The isolates were resistant to 5'-IdU and ether, but sensitive to acid pH 3.0. There were 12 segments RNA shown by polyacrylamide gel electrophoresis (PAGE) and PAGE profile of the two isolates were similar (6-6). The PAGE profile was also similar to that of the TRT2 strain isolated in 1991, but there were at least 8 segments slightly different between the new isolates and TRT2 in band migration distance. Tissue culture cross-neutralization test showed that the new isolates were antigenically related to TRT2 strain identified as coltivirus. Growth curve of the two isolates on C6/36 cells showed that virus titer began to rise at the first day after infection and continued to increase up to 7.0 Log TCID50 per 0.1 ml and maintained a high level until the 21st day after infection. It seems that the virus may cause persistent infection on C6/36 cell.