Comparison of the Clinical and Laboratory Features of COVID and Influenza in Children.

Background and Objectives: Coronavirus disease 2019 (COVID-19) is caused by SARS-CoV-2 and has a clinical presentation ranging from an asymptomatic course to flu-like syndrome up to respiratory failure. Seasonal Influenza, due to the influenza viruses and very common in children, can cause symptoms similar to COVID-19. In order to identify clinical and laboratory characteristics that allow healthcare workers to differentiate COVID-19 from Influenza, we performed a systematic review of the existing literature on the pediatric age. Methods. The research was done via PubMed for articles published from March 2020 to October 2021, combining the MeSH words "COVID-19" and "Influenza" and "Children" and considering the suggestions of the PRISMA Group. Results: The most frequently described symptoms were fever and cough in both groups. In most studies, high fever, cough, nasal congestion or rhinorrhea, vomiting, and muscle pain were detected more frequently in the Influenza group. Regarding the value of laboratory tests, the results were mixed. Almost all studies reported significantly lower levels of C-reactive protein and procalcitonin in the COVID-19 group than in the Influenza group. In most manuscripts, COVID-19 had a milder course than Influenza. Conclusions: No symptoms are characteristic of a single infectious agent, with flu-like disorders being the most common. In addition, laboratory tests do not help in the differential diagnosis; however, they show a limited inflammatory response in COVID-19, which could explain the fewer complications compared to adulthood, with a less severe clinical course.