The aim: To determine the frequency of HSV1, HSV2, VZV, CMV, EBV, HHV6 and influenza virus detection in patients with ischemic stroke in different seasons. Materials and methods: 144 patients with ischemic stroke were examined: 78 (54.2%) women and 66 (45.8%) men, mean age of 63.1 ± 0.8 years. Detection of the herpesvirus DNA and the influenza virus RNA was performed using PCR monthly in 12 patients. Results: A manifestation of a viral infection was detected in 32 (22.2%) and virus genomes were

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... observed in 29 (90.6%) patients. Viral infection frequency is significantly lower in summer, compared to winter-autumn; p=0.033. HSV1 and HHV6 were the most common (19 (52.8%) and 16 (44.4%)); VZV was the least common (5 (13.9%)). Influenza virus RNA was detected in 10 (27.8%) patients. In winter-autumn the frequency of HSV1, HSV2, HHV6 viruses detection is significantly higher, compared to the spring-summer (p<0.05), and the difference is almost significant for the influenza virus (p=0.060) and the EBV (p=0.060). Association of stroke occurrence with the presence of two or more types of viruses is more common in winter, compared to the summer season: 11 (30.6%) vs. 3 (8.3%), p=0.017. Conclusions: Prevention and treatment of herpesvirus infections exacerbations, in particular HSV1 and HSV2, which significantly increase in winter, compared to summer, is an important direction of stroke prevention measures in risk groups.