Molecular Epidemiology of Varicella‐Zoster Virus Among Patients From Two French Tertiary Care Hospitals: Differential Distribution of Clades According to Demographic Criteria

Varicella-zoster virus (VZV) nomenclature currently recognizes seven established clades (designated 1-6 and 9). A geographical segregation of VZV clades has been shown, with Clades 1, 3, and 6 predominating in Europe, Americas, and Australia, Clade 2 in Japan and East-Asia, and Clades 4 and 5 in Asia and Africa. This distribution of VZV clades is dependent on the importation of viral strains, because of immigration and travels, and the implementation of varicella vaccine. The surveillance of VZV epidemiology is therefore necessary. VZV genotyping strategies rely on evaluating a panel of single nucleotide polymorphisms (SNPs) across the different open reading frames (ORFs) of the viral genome. We described retrospectively the VZV clade distribution among 339 patients in Pitié-Salpêtrière (Paris) and Bordeaux University hospitals from 2018 to 2023. Clade 1 was detected in 27.1%, Clade 3 in 37.2%, Clade 5 in 31.9%, and other clades in 3.8% of the patients. The distribution of clades did not differ according to sex, immune status of the patients, and clinical presentation of VZV infection. However, patients infected with Clade 5 were statistically younger than those infected with other clades, especially European-born patients. This epidemiological characteristic of VZV Clade 5 may have multifactorial etiology, including the combination of viral, host, and environmental factors.