November 3, 2024 Situation with parvovirus B19 in France.

November 3, 2024

The epidemic of infections caused by parvovirus B19 (B19V) began in May 2023, affecting all age groups and, in particular, children. Its intensity increased in the last quarter of 2023 and reached its peak in March 2024. The causes of this epidemic are not precisely established, but like other viral or bacterial infections, it may have been related to the lifting of sanitary measures (particularly quarantine and barrier measures) that followed the Covid pandemic, during which an immunity debt may have developed.

This epidemic has affected France with different intensity depending on the region. This was also observed in other European countries. It is characterized by a high incidence of infections, recorded by various data sources. It was responsible for significant morbidity, especially among pediatric patients, with more severe pediatric cases admitted to intensive care units. A survey of hospital virology laboratories conducted in April 2024 showed an increase in maternal-fetal infections in 2023 and 2024, confirming the impact of this epidemic on the increase in maternal-fetal B19V infections and intrauterine fetal mortality. The number of deaths caused by B19V was higher than in previous years but remains relatively low.

Since April 2024, surveillance has shown a decrease in all regularly monitored epidemiological indicators: a decrease in the number of positive B19V serologies and positivity rates; reduction in emergency department visits and outpatient consultations due to B19V infection. At the end of September 2024, the monthly incidence of B19V infections was very similar to that in the pre-epidemic period (171 IgM-positive in September 2024 versus 188 in September 2019). The positivity rate of 8% in September 2024 (4% in September 2019) has fallen steadily since March 2024 (20%).

In 2024, as of September 30, the number of deaths associated with B19V infection was 10. Six deaths occurred in children, five of which occurred between January and April; These five deaths involved children under one year of age, including four newborns following congenital infection. Four adult deaths occurred between April and August. This figure of 10 deaths is higher than the average of 1.8 annually before the Covid-19 pandemic, when deaths mainly affected adults.

French public health will closely monitor the development of the disease using certain established indicators in order to detect a second wave of the epidemic if necessary. However, given the intense level of B19V circulation over the past two years, it is likely that the epidemiological situation will normalize and return to the usual trends of annual transmission with a moderate resurgence in late winter and early spring.

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