Clinical and virological impacts of human parvovirus B19 epidemics on fulminant myocarditis in childhood.

BACKGROUND

Outbreaks of pediatric myocarditis and increased activity of human parvovirus B19 (B19V) have been reported worldwide following the coronavirus disease 2019 (COVID-19) pandemic. However, the direct association between prevalent erythema infectiosum and fulminant myocarditis (FM) remains elusive because of the lack of surveillance data. This study aimed to evaluate the incidence of pediatric FM during the prolonged period and to characterize B19V genotypes and clinical outcomes of the positive cases for improved disease control.

METHODS

Pediatric patients with FM retrospectively underwent clinical and comprehensive virological analyses at one of the largest tertiary centers in Japan from 2009 to 2024, encompassing three epidemic periods of erythema infectiosum. The incidence of FM with and without B19V infection was analyzed using a Poisson regression model. Clinical and laboratory findings were compared between B19V-positive and B19V-negative patients. Genotypic variations of the isolated B19V strains were also examined.

RESULTS

Twenty-one (median age: 5 years, range: 1 month–14 years) of 33 patients underwent viral study. Eight (38%) patients were positive for B19V DNA (1.15–6.11 log10 copies/ml). The incidence of B19V-positive FM in the three epidemic periods was significantly greater than that in the other study periods (1.33/year vs. 0.26/year, incidence rate ratio: 5.1 [1.2–21], p = 0.03). The youngest B19V-positive patient was a 4-month-old infant with a sufficient B19V-specific IgG level at presentation. B19V-specific IgM levels were positively correlated with the viral loads under the cutoff diagnostic index for erythema infectiosum (correlation coefficient: 0.970, p = 0.0005). B19V-positive patients showed higher cardiac enzyme levels, lower ejection fractions on admission, and higher mortality rates (50% vs. 15%) than B19V-negative patients. However, no cardiac outcomes differed among survivors. All six isolated B19V strains belonged to the genotype 1, representing the background virus strains isolated from five non-myocarditis controls.

CONCLUSIONS

B19V-induced FM associated with epidemic strains, causing severe myocardial destruction. Rapid circulating B19V DNA testing rather than serologic testing helps guide intensive intervention for pediatric myocarditis.