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. 2025 Mar 27:153:e57.
doi: 10.1017/S0950268825000275.

Risk factors for invasive group A streptococcal infection in children aged 6 months to 5 years: a case-control study, the Netherlands, February-May 2023

Elizabeth I Hazelhorst  1   2 , Catharina E van Ewijk  1 , Cornelia C H Wielders  1 , Margreet J M Te Wierik  1 , Susan J M Hahné  1 , Hester E de Melker  1 , Mirjam J Knol  1 , Brechje de Gier  1
Affiliations

Risk factors for invasive group A streptococcal infection in children aged 6 months to 5 years: a case-control study, the Netherlands, February-May 2023

Elizabeth I Hazelhorst et al. Epidemiol Infect. .

Abstract

In 2022, an increase in invasive group A streptococcal (iGAS) infections was observed in the Netherlands. A particular increase was seen among children; therefore, we aimed to assess risk factors for iGAS infection in children aged 6 months to 5 years. A prospective case-control study was conducted between February and May 2023. We approached parents of notified iGAS cases to complete a questionnaire on exposures during 4 weeks prior to disease onset. Controls were recruited via social media and matched to cases on sex and birthyear. Conditional logistic regression was performed to estimate odds ratios (OR) of exposures. For the analysis, we included 18 cases and 103 controls. Varicella prior to onset of iGAS disease was reported in two (11%) cases and one (1%) control (OR: 12.0, 95% CI: 1.1-139.0). Exposure to group A streptococcal (GAS)-like illnesses such as impetigo, pharyngitis, and scarlet fever was reported in 8 (44%) cases and 15 (15%) controls (OR: 7.1, 95% CI: 1.8-29.0). Our findings are in line with previous studies by identifying varicella as a risk factor for iGAS among young children and highlight the association with non-invasive GAS infections in the community as a possible source of transmission.

Keywords: Case-control; children; groep A streptococcal disease; iGAS; risk factors; streptococcus pyogenes.

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Conflict of interest statement

Author S.H. is editor-in-chief of journal Epidemiology and Infection. The remaining authors declare no competing interests exist.

Figures

Figure 1.
Figure 1.
Process from recruitment (February - May 2023) of cases and controls to final dataset for analysis.
See this image and copyright information in PMC

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