Severe myocarditis increase in children associated with parvovirus B19 infection : MYKKE registry and German surveillance data

Abstract

Background Following a surge in myocarditis in Germany since August 2023, many with parvovirus B19 (B19V) detection, concerns arose about causes and countermeasures. Objectives The authors aimed to verify the association among B19V, myocarditis increase, and severity. Methods Data from the pediatric multicenter registry (MYKKE) from 27 centers were analyzed. B19V myocarditis cases were defined by polymerase chain reaction (PCR) positivity in blood or myocardium with clinical or histopathologic myocarditis evidence. Comprehensive clinical, histopathologic, and epidemiologic analyses were conducted. Past patients were hospitalized from 2013 to July 2023, current from August 2023 to November 2024. Registry data were compared with surveillance and consultant laboratory data. Specimens of current cases underwent metagenomic analysis and B19V sequencing. Results Since 2013, 922 myocarditis patients including 126 (13.6%) with B19V myocarditis were enrolled. With 57 of 126 (45.2%) current cases, B19V myocarditis increased, compared with other myocarditis causes. Most current cases were patients who were <2 years of age (64.9%), 56.1% were female. The ratio of B19V myocarditis to incidence did not increase compared with the earlier period. Current cases presented with more reduced ejection fraction (29.0% vs 34.5%; P = 0.007), linked to severe cardiac T-cell infiltration and high numbers of B19V copies. Increased severity was associated with younger age. Phylogenetic analysis identified B19V genotype 1A, without sequence variants indicating increased virulence. Conclusions The increase in pediatric myocarditis since August 2023 was associated with B19V, more likely explained by disproportionately young current cases and young children’s vulnerability than a virulent strain. Raising clinicians’ awareness and proactive, interdisciplinary approaches are essential for improving prevention of B19V infection, management of myocarditis, and treatment strategies in this vulnerable cohort.