# Impact of COVID-19 on the epidemiology of severe sinogenic and otogenic infections and their intracranial complications

## TL;DR

This study shows that after the COVID-19 pandemic, there was a significant rise in hospital cases of mastoiditis and orbital cellulitis in children, possibly due to immunity debt and changes in respiratory bacteria.

## Contribution

The study reveals a significant post-pandemic increase in pediatric mastoiditis and orbital cellulitis cases, likely linked to immunity debt and microbiota changes.

## Key findings

- Post-pandemic in-hospital incidence of mastoiditis and orbital cellulitis in children increased significantly compared to pre-pandemic.
- Rates of intracranial complications from orbital cellulitis were lower post-pandemic compared to pre-pandemic.
- Streptococcus and Staphylococcus species were the most common pathogens across all periods.

## Abstract

This study aims to evaluate the impact of COVID-19 pandemic on the incidence, microbiological characteristics, management, and outcomes of mastoiditis and orbital cellulitis and their intracranial complications in pediatric patients. A retrospective observational study was conducted at the major pediatric hospital of Athens from 1/2018 to 12/2023. Pediatric patients (0–16 years) diagnosed with mastoiditis, orbital cellulitis, and related complications were included. Data were collected across three periods: pre-pandemic (1/2018–3/2020), during the pandemic (4/2020–6/2021), and post-pandemic (7/2021–12/2023). Statistical analyses compared demographic, clinical, and microbiological characteristics between the periods. A total of 176 cases were included (76 mastoiditis and 100 orbital cellulitis cases). The in-hospital incidence of both infections increased significantly post-pandemic compared to the period before the pandemic (mastoiditis: 5.5 vs.13.6 per 1000 admissions; orbital cellulitis: 4.8 vs. 21.8 per 1000 admissions, P < 0.001). Streptococcus and Staphylococcus species predominated across the three periods. Median (IQR) age was not significantly different between the two periods among patients with mastoiditis (pre-pandemic: 5.6 (3.5) years vs. post-pandemic: 3.3 (3.4) years, P = 0.12) and among patients with orbital cellulitis (pre-pandemic: 9.2 (6.6) years vs. post-pandemic: 8 (9.2) years, P = 0.50). Regarding the complications, the rate of intracranial empyema/abscess development among patients with orbital cellulitis, but not mastoiditis, was lower post-pandemic compared to pre-pandemic (30% vs. 10.1%, P = 0.03).

Conclusion: The study findings demonstrate a significant rise in the post-COVID-19 in-hospital incidence of mastoiditis and orbital cellulitis in children. Future epidemiological surveillance of these complications and pathogen-specific dynamics, are important to develop prevention strategies for these severe pediatric infections.
What is Known:• The COVID-19 pandemic shifted the epidemiology of severe upper respiratory tract infections.• Data on the epidemiology of severe sinogenic and otogenic infections and their intracranial complications during and after the acute phase of the COVID-19 pandemic are limited in Europe.What is New:• This study highlights a notable increase in the in-hospital incidence of mastoiditis and orbital cellulitis during the post-COVID-19 pandemic era, likely associated with immunity debt and alterations in respiratory microbiota.• Despite the increase in pediatric mastoiditis and orbital cellulitis cases, the rates of complications and surgical management remained stable throughout the study period.

The online version contains supplementary material available at 10.1007/s00431-025-06188-4.