Tehran University of Medical Sciences Iranian Journal of Microbiology 2008-3289 13 1 2021 02 10 23 30 Juana del Valle-Mendoza Molecular and Cell Biology Laboratory, Research and Innovation Centre of the Faculty of Health Sciences, Universidad Peruana de Ciencias Aplicadas, Lima, Peru; Department of Medicine, Faculty of Health Sciences, Universidad Peruana de Ciencias Aplicadas, Lima, Peru; Molecular Biology Laboratory, Instituto de Investigación Nutricional, Lima, Peru Cristina del Valle-Vargas Department of Medicine, School of Medicine, Univesidad de Barcelona, Barcelona, Spain Ronald Aquino-Ortega Molecular and Cell Biology Laboratory, Research and Innovation Centre of the Faculty of Health Sciences, Universidad Peruana de Ciencias Aplicadas, Lima, Peru; Molecular Biology Laboratory, Instituto de Investigación Nutricional, Lima, Peru Luis del Valle Barcelona Research Center for Multiscale Science and Engineering, Departament d’Enginyeria Quıímica, EEBE, Universidad Politècnica de Catalunya (UPC), Barcelona, Spain Erico Cieza-Mora Peditric Unit, Hospital Regional Docente de Cajamarca, Cajamarca, Peru Wilmer Silva-Caso Molecular and Cell Biology Laboratory, Research and Innovation Centre of the Faculty of Health Sciences, Universidad Peruana de Ciencias Aplicadas, Lima, Peru; Department of Medicine, Faculty of Health Sciences, Universidad Peruana de Ciencias Aplicadas, Lima, Peru; Molecular Biology Laboratory, Instituto de Investigación Nutricional, Lima, Peru; Comité del Médico Joven-Consejo Nacional, Colegio Médico del Perú, Lima, Peru Jorge Bazán-Mayra Molecular Biology Laboratory, Laboratorio Regional de Cajamarca, Dirección Regional de Salud de Cajamarca (DIRESA), Cajamarca, Peru Victor Zavaleta-Gavidia Molecular Biology Laboratory, Laboratorio Regional de Cajamarca, Dirección Regional de Salud de Cajamarca (DIRESA), Cajamarca, Peru Miguel Angel Aguilar-Luis Molecular and Cell Biology Laboratory, Research and Innovation Centre of the Faculty of Health Sciences, Universidad Peruana de Ciencias Aplicadas, Lima, Peru; Department of Medicine, Faculty of Health Sciences, Universidad Peruana de Ciencias Aplicadas, Lima, Peru; Molecular Biology Laboratory, Instituto de Investigación Nutricional, Lima, Peru Hernán Cornejo-Pacherres Molecular Biology Laboratory, Laboratorio Regional de Cajamarca, Dirección Regional de Salud de Cajamarca (DIRESA), Cajamarca, Peru Johanna Martins-Luna Molecular and Cell Biology Laboratory, Research and Innovation Centre of the Faculty of Health Sciences, Universidad Peruana de Ciencias Aplicadas, Lima, Peru; Molecular Biology Laboratory, Instituto de Investigación Nutricional, Lima, Peru Angela Cornejo-Tapia Molecular and Cell Biology Laboratory, Research and Innovation Centre of the Faculty of Health Sciences, Universidad Peruana de Ciencias Aplicadas, Lima, Peru; Department of Medicine, Faculty of Health Sciences, Universidad Peruana de Ciencias Aplicadas, Lima, Peru 2020 04 14 2021 01 06 Background and Objectives: Pertussis is an infectious disease caused by the Gram-negative bacterium Bordetella pertussis. In Peru, actual public health programs indicate that vaccination against B. pertussis must be mandatory and generalized, besides all detected cases must be reported. The objective of this study was to determine the prevalence of B. pertussis among children under five years of age with a presumptive diagnosis of whopping cough in Cajamarca, a region located in northern Peru. Materials and Methods: The population of this cross-sectional study were children under 5 years old hospitalized as presumptive cases of pertussis during December 2017 to December 2018. The nasopharyngeal samples were analyzed by real-time PCR for the detection of B. pertussis. Results: B. pertussis was identified as PCR + in 42.3% of our sample (33/78). The clinical presentation that was observed most frequently includes paroxysmal coughing (97%), difficulty breathing (69.7%), cyanosis (72.7%) and post-tussive emesis (60.6%). Additionally, pneumonia was the most observed complication (33.3%). Four of the patients with PCR+ for B. pertussis presented only lymphocytosis, five only leukocytosis, two patients with decreased leukocytosis and lymphocytes and only one patient with leukopenia and relative lymphocytosis. There was a percentage of 84.8% of unvaccinated children in the PCR+ group. Finally, the mother was the most frequent symptom carrier (18.2%). Conclusion: In conclusion, in the studied population there is a high rate of PCR+ cases for B. pertussis. Laboratory values may show leukopenia or lymphopenia in patients with pertussis. It is necessary to use appropriate laboratory diagnostic tests in all infants with respiratory symptoms for B. pertussis. Since, the clinical diagnosis overestimates the diagnosis of pertussis. https://ijm.tums.ac.ir/index.php/ijm/article/view/2581 https://ijm.tums.ac.ir/index.php/ijm/article/download/2581/1312