Genotyping of Varicella Zoster Virus Clinical Isolates from the Czech Republic.

Varicella zoster virus (VZV) is a highly contagious human pathogen. Virus causes varicella (chickenpox) as a primary infection during which a lifelong latent infection is established. It is easily passed through airborne particles, droplets in exhaled air and fluids from blisters or sores. Virus can be also transmitted indirectly by a contact with articles of clothing and other items exposed to virus (1). Around 45,000 cases of varicella are reported each year in the Czech Republic, which makes it the most frequent type of virus infection. The group infected most frequently in our temperate climate are children under 10 years of age (2). In adults, complications are more frequent in pregnant women, with negative consequences for the foetus and the newborns, and in immunocompromised people with an increased risk of mortality. Immunocompromised patients may develop severe skin eruptions with or without hemorrhage. Healing of the cutaneous lesions takes longer than in the general population. Patients often develop high fever. Virus spreads to visceral organs causing hepatitis, pneumonitis, pancreatitis, and encephalitis. Bacterial superinfections (Streptococcus pneumoniae, Haemophilus influenzae, Staphylococcus aureus) including bacteremia can develop (3). A lifelong latent infection can reactivate, typically after the age of fifty, to cause herpes zoster (shingles). Herpes zoster occurs frequently in adults, but is not uncommon in immunocompromised and even normal children. In addition herpes zoster could be responsible for a wide spectrum of serious health complications. Immunocompromised patients can experience more severe forms of the disease. Lesions form for up to 2 weeks after infection and scabbing occurs until 3 to 4 weeks into the course of the disease. Patients with lymphoproliferative malignancies are at risk of cutaneous dissemination and visceral involvement, including pneumonitis, hepatitis, and meningoencephalitis. Around ten percent of patients with HIV can be infected with zoster. These patients can develop chronic herpes zoster, with formation of new lesions without healing of the already existing ones (4). From 2009 to 2016, we examined 1,074 outand inpatients with varicella (623 patients, 2.9% of immunocompromised) or herpes zoster (451 patients, 7.9% of immunocompromised) treated in the Faculty Hospital Hradec Králové. Characterization of individual short VZV DNA sequences was performed utilizing PCR and sequencing. Single nucleotide polymorphisms (SNP) in open reading frames (ORF) 21, 22 and 50 were used to identify individual VZV strains (Table 1). All clinical isolates were VZV positive wild-type strains. The phylogenetic analysis showed that 33.7% of the clinical isolates were European clade 1 (C/E1strain) and 65.7% were European clade 3 (B/E2 strain). In this large cohort we have found six patients (0.6%) infected with clade 5(A/M1strain). This clade is found mostly throughout Africa and India. Five of these clinical isolates were adults with manifestations of herpes zoster. The sixth case was 8 years old immunocompromised girl with varicella. Child was vaccinated by only one dose (instead of two) of Varilrix at the age of two. Varicella vaccination is not included in the Czech National Immunization Programme for children. The vaccination rate in Czech children is very low, around 1‒2%. This clinical sample was genotyped by sequencing as clade 5 containing unique SNP at position 95 333 nt (ORF 54) – T>C (5‒8). In the Czech Republic, the most common clades of VZV are European clades 1 and 3. Similar data have been repeatedly reported in Germany. They have shown 85% prevalence of clade 1 and 3 and nearly 20% of clade 1 replaced by clade 5 in primary VZV infection. Our findings of clade 5 in the Czech population support their hypothesis that the spread of clade 5 has been continuing throughout the European continent (9, 10).