In 1995 a prospective clinical, epidemiological and virological study was launched on severe viral respiratory infections in children admitted to the Paediatrics Department of Hospital Severo Ochoa, in close collaboration with the Influenza and Respiratory Virus Laboratory of the Centro Nacional de Microbiología, Instituto de Salud Carlos III de Majadahonda (ISCIII). Throughout these years, prospective collection of clinical data has been established for all paediatric patients admitted with a respiratory infection, as well as a system for collecting and transporting respiratory samples from all patients for virological study by immunofluorescence and RT-PCR at the Influenza and Respiratory Virus Laboratory of the Centro Nacional de Microbiología, ISCIII.
This line of research and group, now fully established, has progressively expanded its scope. Following the discovery of new respiratory viruses from 2001 onwards, our study also included the clinical and epidemiological characteristics of infections caused by these emerging viruses: human metapneumovirus, bocavirus, coronavirus and new rhinovirus groups.

Subsequently, this line of research also aimed to assess the possible impact of severe bronchiolitis, caused by different respiratory viruses, on the subsequent development of recurrent respiratory disease, mainly recurrent wheezing and asthma in childhood, with long-term follow-up of patients admitted in the first months of life.

Lastly, in the last four years our group has launched a prospective study of the role of viral respiratory infections in premature newborns admitted to the Neonatal Intensive Care Unit, and of the immune response and microbiota in the onset of respiratory symptoms during admission and in the development of recurrent respiratory disease in the medium term.

Keeping the original group, made up as already mentioned of the Paediatrics Department of the Hospital Universitario Severo Ochoa and the Influenza and Respiratory Virus Laboratory of the Centro Nacional de Microbiología (ISCIII), new researchers have gradually joined, allowing a deeper understanding of other factors, such as the immune response to viral infections or the host's respiratory and digestive microbiota. Thus, since 2015 researchers from the Immunology Department of the Instituto de Investigación Sanitaria de la Fundación Jiménez Díaz (IIS-FJD) have been part of our group, and since 2019, researchers from the Lactic Bacteria and Probiotics Group of the Instituto de Agroquímica y Tecnología de los Alimentos of the Centro Superior de Investigaciones Científicas (IATA-CSIC).

This line of research has been funded by successive Fondo de Investigaciones Sanitarias (FIS) projects and has resulted in several doctoral theses, final degree projects and numerous national and international publications, which have established our group as a national reference in clinical research on viral respiratory infections in children.

Currently, 6 members of our group are part of the CIBER Infectious Diseases and CIBER Respiratory Diseases groups.

Following the addition of immunologists from the IIS-FJD to our group, we expanded the study of the immune response not only to severe respiratory infections and asthma, but also to another disease whose pathogenic mechanisms are not well understood, but which is increasingly diagnosed in childhood: eosinophilic oesophagitis. Thus, the paediatric gastroenterologists in our department, in collaboration with the immunologists from the IIS-FJD, have implemented an already established line of research focused on studying this disease: its incidence and epidemiological factors; the influence of the patient's microbiota on clinical presentation and treatment response, as well as the molecular and pharmacological mechanisms of action of proton pump inhibitors in eosinophilic oesophagitis.