A new epidemic wave of Bordetella pertussis in paediatric population: impact and role of co-infections in pertussis disease

BackgroundIn recent months, Bordetella pertussis has reappeared after maintaining a low rate for many years. Although pertussis is usually characterized by a favorable course, several factors can contribute to the severity of the disease, such as mixed respiratory infections. In this study, we evaluate B.pertussis cases observed in the pediatric population followed at the Bambino Ges \& ugrave; Children's Hospital and analyzed the potential impact of co-infections in relation to disease severity.MethodsFrom January to May 2024, a total of 1,151 children and adolescents (both inpatients and outpatients) were screened for the presence of respiratory pathogens, including B.pertussis, with clinically relevant respiratory symptoms. Results: Among the 1,151 patients screened, 66 tested positive for B.pertussis. Fourteen patients had respiratory failure, and six of them required intensive care unit (ICU) admission, while 52 had mild infection. 23.3\% of patients had B.pertussis alone, while 76.7\% had co-infections (including 5 patients admitted to the ICU). A higher co-infection rate was observed in patients with respiratory failure than in those without failure (92.9\% vs. 69.0\%, p-value:0.041). Rhinovirus, Metapneumovirus and Parainfluenza-virus were the most prevalent in our pediatric population. Co-infections of human bocavirus with B.pertussis were observed exclusively in patients with respiratory failure. Conclusions: Our results highlighted an increase in B.pertussis cases from January to May 2024, reaching a peak of cases in the month of May. This study shows a high rate of B.pertussis co-infection, and a trend toward association between B.pertussis and specific viruses, that might play a role in increasing disease severity.