# Pertussis–SARS-CoV-2 Co-infection in Infants at Mohammed VI University Hospital, Marrakech, Morocco

## TL;DR

This study reports rare but clinically significant cases of infants in Morocco co-infected with pertussis and SARS-CoV-2, highlighting the importance of rapid diagnostic testing.

## Contribution

The study provides the first clinical description of pertussis-SARS-CoV-2 co-infection in infants using a multiplex PCR approach.

## Key findings

- Nine infants under 24 months were diagnosed with pertussis-SARS-CoV-2 co-infection.
- Common symptoms included respiratory distress, oxygen desaturation, and elevated CRP levels.
- Syndromic PCR testing enabled early diagnosis and treatment, reducing transmission risks.

## Abstract

Background: Viral-bacterial co-infections may worsen the clinical course of COVID-19; however, the clinical characteristics of pertussis co-infection with SARS-CoV-2 in infants remain poorly described.

Methods: We conducted a retrospective study (from January 2024 to September 2025) at Mohammed VI University Hospital in Marrakech. Infants younger than 24 months with clinical suspicion of pertussis underwent multiplex respiratory polymerase chain reaction (PCR) testing using the FilmArray Respiratory Panel 2.1 plus panel (BioMérieux, Marcy-l'Étoile, France). Co-infection was defined as the simultaneous detection of Bordetella pertussis and SARS-CoV-2 from the same nasopharyngeal specimen. Demographic, clinical, laboratory, and radiological data, as well as treatment and outcomes, were collected. Comparisons between groups were performed using Fisher’s exact test for categorical variables.

Results: Among 628 tested patients (including 419 children), 69 were diagnosed with pertussis. Nine infants (mean age: 0.08 years) had pertussis-SARS-CoV-2 co-infection. Typical pertussis features were present in all patients. Common findings included respiratory distress (6/9), oxygen desaturation requiring supplemental oxygen (4/9), wheezing (4/9), elevated C-reactive protein (CRP) (5/9), leukocytosis (9/9), lymphocytosis (7/9), including one case of marked lymphocytosis, and thrombocytosis (8/9), with platelet counts ≥ 600 G/L in three cases. Chest imaging revealed interstitial patterns (1/9), focal infiltrate (1/9), or hyperinflation (2/9). The median length of hospital stay was four days.

Conclusion: Pertussis-SARS-CoV-2 co-infection in early infancy is uncommon but clinically relevant. Syndromic PCR enabled prompt diagnosis, early initiation of macrolide therapy, and rapid implementation of isolation to limit transmission. Larger studies are needed to better define severity determinants and identify gaps in vaccine-preventable disease coverage.