[Viral respiratory tract infections in the first six months of life]

Respiratory syncytial virus and Influenza virus infections are known causes of hospital admission in infants. It is less well known the pattern of virus infections in infants under 6 months of age in the outpatient setting.

To describe the clinical and epidemiological pattern of community-acquired viral respiratory infections in infants under 6 months.

A cohort of infants from the 8 and 9 Madrid Health Districts was followed by telephone calls every two weeks since birth during the epidemic winter season. Clinical and epidemiological data were collected in pre-designed questionnaires. Nasopharyngeal aspirate was obtained in every patient with symptoms compatible with respiratory infection. Diagnosis of the more common virus was made with direct immunofluorescence and nucleic acid amplification test (PCR).

Were recruited 316 newborns. The 1,865 phone calls made (median 4 for every child), produced 106 visits, and the illness confirmed in 89 illness. Rhinitis (91%) and cough (69%) were the most common symptoms. Upper respiratory infection was the principal clinical diagnosis (84.5%), and 17 of the 72 samples (23.2%) were positive. Most common viruses were RSV (41.1%) and rhinovirus (35.2%). Of the children visited, 17 out of 106 (16%) (5.3% of the cohort) were admitted to hospital. Diagnoses were febrile syndrome and bronchiolitis. We did not find any epidemiological factor associated with viral respiratory infection in positive cases.

In our population most of the respiratory infections in infants are minor and do not need hospital assistance. Rhinovirus and RSV are the major pathogens. We did not find any epidemiological factor associated with viral respiratory infection.