Common Seasonal Pathogens and Epidemiology of Henoch-Schönlein Purpura Among Children

Abstract

Importance: Henoch-Schönlein purpura (HSP) is the most common type of vasculitis in children. The factors that trigger the disease are poorly understood. Although several viruses and seasonal bacterial infections have been associated with HSP, differentiating the specific associations of these pathogens with the onset of HSP remains a challenge due to their overlapping seasonal patterns.

Objective: To analyze the role of seasonal pathogens in the epidemiology of HSP.

Design, setting, and participants: This cohort study comprised an interrupted time-series analysis of patient records from a comprehensive national hospital-based surveillance system. Children younger than 18 years hospitalized for HSP in France between January 1, 2015, and March 31, 2023, were included.

Exposure: Implementation and relaxation of nonpharmaceutical interventions (NPIs) for the COVID-19 pandemic, such as social distancing and mask wearing.

Main outcomes and measures: The main outcomes were the monthly incidence of HSP per 100 000 children, analyzed via a quasi-Poisson regression model, and the estimated percentage of HSP incidence potentially associated with 14 selected common seasonal pathogens over the same period.

Results: The study included 9790 children with HSP (median age, 5 years [IQR, 4-8 years]; 5538 boys [56.4%]) and 757 110 children with the infectious diseases included in the study (median age, 0.7 years [IQR, 0.2-2 years]; 393 697 boys [52.0%]). The incidence of HSP decreased significantly after implementation of NPIs in March 2020 (-53.6%; 95% CI, -66.6% to -40.6%; P < .001) and increased significantly after the relaxation of NPIs in April 2021 (37.2%; 95% CI, 28.0%-46.3%; P < .001). The percentage of HSP incidence potentially associated with Streptococcus pneumoniae was 37.3% (95% CI, 22.3%-52.3%; P < .001), the percentage of cases associated with Streptococcus pyogenes was 25.6% (95% CI, 16.7%-34.4%; P < .001), and the percentage of cases associated with human rhino enterovirus was 17.1% (95% CI, 3.8%-30.4%; P = .01). Three sensitivity analyses found similar results.

Conclusions and relevance: This study found that significant changes in the incidence of HSP simultaneously with major shifts in circulating pathogens after NPIs for the COVID-19 pandemic indicated that approximately 60% of HSP incidence was potentially associated with pneumococcus and group A streptococcus. This finding suggests that preventive measures against these pathogens could reduce the incidence of pediatric HSP.

Figure 1.. Association of Nonpharmaceutical Intervention (NPI) Implementation and Lifting With the Monthly Incidence of Henoch-Schönlein Purpura and Acute Pyelonephritis per 100 000 Children Younger Than 18 Years in France, January 2015 to March 2023

A, Monthly incidence of Henoch-Schönlein purpura per 100 000 children younger than 18 years (n = 9790). B, Monthly incidence of acute pyelonephritis per 100 000 children younger than 18 years (n = 177 791). The dark blue line shows the observed data. The light blue line shows the model estimates based on observed data using the quasi-Poisson regression model. The orange line shows the expected values without NPI implementation using the same quasi-Poisson model. The light blue and orange shaded areas indicate the 95% CIs. The dotted vertical lines indicate the implementation of the NPIs in March 2020 and the lifting of NPIs in April 2021.

Figure 2.. Seasonal Pattern of the Incidences of Henoch-Schönlein Purpura (HSP) and Streptococcus pneumoniae and of HSP and Streptococcus pyogenes Infections per 100 000 Children Younger Than 18 Years in France

A, Incidences of HSP and S pneumoniae infections (n = 9037) per 100 000 children younger than 18 years. B, Incidences of HSP and S pyogenes infections (n = 8576) per 100 000 children younger than 18 years. The dark blue line shows the monthly incidence of HSP per 100 000 children.