RESUMO
Respiratory Syncytial Virus (RSV) is the main cause of acute lower respiratory tract infections in children under 2 years, its distribution is worldwide and even in very different climatic conditions, it appears to have similar features, certainly knowing it will produce a significant amount of infections each year. We present the results of a retrospective review of positive cases for RSV detected in the Microbiology Laboratory of the Hospital Clinico Universitario of Valladolid in the period between 1990 and 2000, dealing with its presentation at the given time with the weather variables of temperature and humidity. Every year, we have observed as the clustering of cases was associated with two outbreaks, one at the beginning and the other at the end of the year, coinciding with the coldest and wettest months. This pattern has been repeated every revised year, according to an annual rate, with the onset of the first insulation between the months of October and February, and of the last ending between March and June, showing the highest peaks of isolation during the month of February. Therefore, every year we observe a break or seasonal slip matching the months with higher temperatures and lower humidity.