Parvovirus B19 in Children: Clinical Spectrum, Viral Load Patterns, and Atypical Cutaneous Presentations in the Post-Pandemic Outbreak

<b>Background:</b> Human parvovirus B19 causes a broad spectrum of clinical manifestations, ranging from the classic "fifth disease" to severe presentations. Clinical presentation varies considerably across age groups. In 2023-2024, a notable increase in parvovirus B19 cases was reported across Europe. <b>Methods:</b> We retrospectively analyzed pediatric patients with serum serology and/or plasma PCR-confirmed parvovirus B19 infection treated at the tertiary infectious diseases center (University Hospital for Infectious Diseases, Zagreb) in 2023 (January-August). Demographic, laboratory, viral load, and clinical characteristics were assessed, with emphasis on cutaneous manifestations. <b>Results:</b> A total of 102 patients were included (median age 10 years; 54.9% male), of whom 7.8% required hospitalization. Rash was present in 94 (92.2%) of the patients of whom 75 had erythema infectiosum and petechiae, while the rest had a combination of both. Patients with petechial rash were significantly older (<i>p</i> = 0.013) and exhibited lower platelet counts (<i>p</i> < 0.001) compared with those with erythema. A higher proportion of anti-B19V IgM (<i>p</i> = 0.027) and IgG (<i>p</i> < 0.001) antibodies was detected in patients with erythema. Petechial rash was associated with higher viral loads (<i>p</i> < 0.001). In univariate analysis, the presence of anti-B19V IgG antibodies was correlated with the absence of petechial rash (OR = 0.09; <i>p</i> < 0.001), whereas higher viral load was associated with its presence (OR = 1.7; <i>p</i> < 0.001). In multivariate analysis, viral load emerged as the only predictor of petechial rash (aOR = 1.4, <i>p</i> = 0.042). <b>Conclusions:</b> Parvovirus B19 remains a self-limiting illness in healthy children, despite frequent atypical presentations. Higher viremia is associated with atypical rash morphology and suggests age-related differences in immune clearance.