Parvoviruses at the Heart: Endothelial Injury and Myocyte Lysis in Human B19V and Canine CPV-2 Infections

Background: Parvovirus B19 (B19V; Erythroparvovirus primate 1) is now the most commonly detected virus in human endomyocardial biopsies from patients with myocarditis or dilated cardiomyopathy; however, its true causal role remains uncertain. By contrast, Protoparvovirus carnivoran 1, also known as canine parvovirus type 2 (CPV-2), is an apparent cause of myocarditis in neonatal puppies, where it replicates in cardiomyocytes, induces extensive cell death, and often leaves fibrotic scars in survivors. Conclusions: This review compares B19V and CPV-2 from basic biology to clinical expression. Divergent tropism and replication kinetics produce distinct injury patterns: predominantly endothelial and microvascular dysfunction with immune-mediated damage in adult human B19V infection versus direct, age-restricted cardiomyocyte lysis in neonatal CPV-2 infection, often followed by fibrosis. Because parvoviral DNA can persist in cardiac tissue, detection alone does not prove causality. We advocate an “evidence bundle” integrating viral load by quantitative polymerase chain reaction (qPCR), detection of viral transcripts and/or proteins when feasible, spatial co-localization with histological injury, and concordant clinical markers (cardiac troponins and advanced imaging, including cardiac magnetic resonance imaging CMR) to support etiologic attribution and guide management in human and veterinary cardiology.