Emerging infections in children

Introduction:Infectious diseases are a significant cause of morbidity and mortality in children.Methods: Recent studies were reviewed, and new epidemiological and clinical facts of the following emerging infectious diseases are discussed: vaccine-preventable diseases (VPDs), post-COVID syndrome, respiratory syncytial virus (RSV) infections, dengue, and Crimean-Congo hemorrhagic fever (CCHF).Results: Vaccine-preventable diseases: A modelling study which quantified the impact of 50 years of the Expanded Programme on Immunization showed that vaccinations accounted for 40% of the reduction of infant mortality during 1974-2024.Measles vaccines accounted for most of the averted infant morbidity and mortality the past 50 years.Nevertheless, from 2018 onwards, vaccination rates in children have been decreasing in several countries globally, which resulted in local re-emergence of several VPDs and the onset of disruptive outbreaks.Regarding the second topic, post-COVID syndrome, a recent meta-analysis found a prevalence rate of 23.36% in children.Major symptoms in affected children are dyspnea, headache, fatigue, shortness of breath, abdominal pain, concentration difficulties, and sleep disorders.Post-COVID syndrome has a multifactorial pathogenesis, involves most systems, and has a negative impact on child's well-being, school attendance and educational activities.Regarding the third topic, RSV, a comparison of 1451 pediatric cases that occurred 2018-2019 with 1102 cases that occurred in 2023 in China, found that the post-COVID-pandemic group was significantly older, more frequently had fever and complications (acute otitis media, seizures), and more frequently had raised inflammation markers.Overall, the post-COVID RSV cases more frequently developed severe lower respiratory tract infection, were admitted to an intensive care unit, and received invasive mechanical intubation.Similarly, infants with RSV hospitalized in France during the COVID-19 pandemic more frequently received oxygen and remained in-hospital for longer periods compared to infants with RSV hospitalized in the pre-COVID era.A prospective cohort study showed that RSV remains a cause of substantial morbidity, leading to the hospitalization of one in every 56 healthy full-term infants in high-income countries.Regarding dengue, a large school-based cross-sectional serosurvey in Kerala, India among 5236 children 9-12 years old found an overall seroprevalence rate of 30.9%, with wide variation across districts.Advanced age and male sex were significantly associated with higher seroprevalence rates.Of note, 40% of children had IgG antibodies against multiple dengue virus serotypes.Lastly, although CCHF is considered a mild disease in children, a recent study from Turkey found that 12 children with CCHF hospitalized during 2020-2021 developed severe illness (all had hepatosplenomegaly) and highly impaired laboratory findings (inflammation and hemorrhagic markers).