Monitoring prevalence of varicella-zoster virus clades in Germany

The global surveillance of varicella-zoster virus (VZV) clades is an important tool for investigation into viral evolution, host-virus interactions, role of immigration and travel for importation of viral strains as well as possible recombination events between wild- and vaccine-type VZV strains. In this prospective study, comprehensive data on the current distribution of VZV clades in Germany were collected. VZV strains from 213 patients with varicella and 109 with zoster were genotyped using the scattered single-nucleotide polymorphism method on the basis of sequencing open reading frames 1, 21, 22, 37, 50, 54 and 60. In varicella, clade 3 was detected in 45.5%, clade 1 in 30.0%, clade 5 in 21.1% and clade 2 in 0.9% of the cases. The analysis of zoster strains revealed clade 3 in 50.5%, clade 1 in 46.8%, clade 2 and clade 4 in 0.9% of the cases each. Five strains from varicella and one strain from zoster could not be attributed to any of the major and provisional VZV clades. Statistical analysis verified significantly lower frequency of clade 1 and significantly higher frequency of clade 5 in patients with varicella compared to zoster. In addition, varicella patients with clade 5 strains were significantly younger than the patients with clade 3. In conclusion, almost one half of VZV infections in Germany were caused currently by VZV clade 3. In primary VZV infection, nearly 20% of clade 1 has been replaced by clade 5 that might spread more effectively in the population than the European VZV clades.