Differential clinic in children infected by SARS-CoV-2, traceability of contacts and cost-effectiveness of diagnostic tests: Cross-sectional observational study Antia Fiel-Ozores; María Luisa González-Durán; Reyes Novoa-Carballal; María del Mar Portugués-de la Red; Isabel Fernández-Pinilla; Jorge Julio Cabrera-Alvargonzález; Cristina Martínez-Reglero; Sonia Rey-Cao; Ana Concheiro-Guisán;