IntroductionRecent data on influenza C virus indicate a possible higher clinical impact in specified patient populations than previously thought.AimWe aimed to investigate influenza C virus circulation in Germany.MethodsA total of 1,588 samples from 0 to 4 year-old children presenting as outpatients with influenza-like illness (ILI) or acute respiratory infection were analysed retrospectively. The samples represented a subset of all samples from the German national surveillance system for influenza in this age group in 2012–14. The presence of influenza C virus was investigated by real-time PCR. For positive samples, information on symptoms as well as other respiratory virus co-infections was considered. Retrieved influenza C viral sequences were phylogenetically characterised.ResultsInfluenza C viral RNA was detected in 20 (1.3% of) samples, including 16 during the 2012/13 season. The majority (18/20) of influenza C-positive patients had ILI according to the European Union definition, one patient had pneumonia. Viruses belonged to the C/Sao Paulo and C/Kanagawa lineages. Most (11/20) samples were co-infected with other respiratory viruses.ConclusionOur data are the first on influenza C virus circulation in Germany and notably from a European national surveillance system. The low detection frequency and the identified virus variants confirm earlier observations outside a surveillance system. More virus detections during the 2012/13 season indicate a variable circulation intensity in the different years studied. Influenza C virus can be considered for ILI patients. Future studies addressing its clinical impact, especially in patients with severe disease are needed.

The emergence of Variola virus-like viruses by natural evolution of zoonotic Orthopoxviruses, like Cowpox virus (CPXV), is a global health threat. The proteasome is essential for poxvirus replication, making the viral components interacting with the ubiquitin-proteasome system attractive antiviral targets. We show that proteasome inhibition impairs CPXV replication by prevention of uncoating, suggesting that uncoating is mediated by proteasomal degradation of viral core proteins. Although Orthopoxvirus particles contain considerable amounts of ubiquitin, distinct modification sites are largely unknown. Therefore, for the first time, we analyzed globally ubiquitination sites in CPXV mature virion proteins using LC-MS/MS. Identification of 137 conserved sites in 54 viral proteins among five CPXV strains revealed extensive ubiquitination of structural core proteins. Moreover, since virions contained primarily K48-linked polyubiquitin, we hypothesized that core proteins are modified accordingly. However, quantitative analysis of ubiquitinated CPXV proteins early in infection showed no proteasomal degradation of core proteins. Instead, our data indicate that the recently suggested proteasomal regulation of the uncoating factor E5 is a prerequisite for uncoating. Expanding our understanding of poxvirus uncoating and elucidating a multitude of novel ubiquitination sites in poxvirus proteins, the present study verifies the major biological significance of ubiquitin in poxvirus infection.The ubiquitin-proteasome system (UPS) is exploited by members of most virus families 1 and is essential for the replication of different virus families, e.g. Pox-2-4 , Reo-5 and Coronaviridae 6 . As a member of the Poxviridae family the genus Orthopoxvirus (OPV) comprises complex enveloped DNA viruses, including the smallpox-causing Variola virus (VARV), Vaccinia virus (VACV), which was used for smallpox eradication 7 , and several animal-borne viruses with zoonotic potential like Cowpox virus (CPXV) [8][9][10] . Having caused the death of hundreds of millions of people, VARV is the most prominent member of OPV. Although VARV has been eradicated in 1979, it is still a global health threat because of its possible release in the context of a bioterrorist attack and the emergence of VARV-like viruses from circulating OPV by natural evolution 11 . CPXV are well suited to fill the niche that was created by VARV eradication, since it has the largest OPV genome including homologous open reading frames of all VARV genes. Currently, the number of zoonotic infections in Europe caused by CPXV is increasing, illustrating the need for a comprehensive understanding of the virus biology, especially the interaction with the host cell 12,13 .