Seasonality of Respiratory Syncytial Virus (RSV) Bronchiolitis in Children Aged 2 Years or Less Hospitalized in Martinique (French West Indies) a Tropical Area From 2007 to 2018

Respiratory Syncytial Virus (RSV) infections are the leading cause of hospitalization for respiratory distress in infants (50% of children under 1 year of age are infected with the virus, 100% of children under 3 years of age). They are responsible for 66,000 to 199,000 deaths in children under 5 years of age worldwide, and 15,000 to 20,000 hospitalizations in France depending on the year. It is a highly contagious virus whose transmission is both respiratory and by hand and which appreciates humidity to develop.

In temperate regions where this infection has been well studied, it occurs preferentially during the winter, probably favoured by the cold and humidity, as well as by the confinement of individuals during this season. The more the child is young, premature, has a chronic respiratory pathology or congenital heart disease, the more sever the disease. Prevention is based on the injection of a monoclonal antibody (Palivizumab) before the start of the epidemic season and on conventional hygiene measures. But today, little epidemiological data is available for tropical regions and in Martinique, which makes it impossible to understand why, how and when RSV develops on our island. Some epidemiological studies carried out in tropical regions point to the possibility that the humidity in the air would favour viral development and in fact, these epidemics are more frequently found during the rainy season. The humidity level, the number of rainy days, the rate of sunshine and cloud cover, and finally the importance of the wind, could explain a different seasonality from that known in temperate regions (seasonality being linked to the virus circulation patterns and being defined as the ability to re-emerge at the same period from one year to the next).

Research issues A first study carried out at the University hospital of Martinique over a period of 2 years (from July 1, 2007 to December 31, 2008) has made it possible to specify the epidemiology a little better but the results need to be confirmed. This work seems to show that the epidemic starts earlier than in temperate zones: (late August - early September to late November - early December) versus (November - December to March - April) respectively. The number of cases per epidemic can change significantly (factor 2.5). However, this first study was not long enough to ensure that the seasonality identified will be systematically repeated from one year to the next. Moreover, this study did not allow us to specify the number of children with clinical severity criteria on our island.

By carrying out a study over a longer period, the investigators will have a better understanding of seasonality and the rate of disease in children in Martinique, allowing us to better anticipate the extent and severity of these phenomena. This precision will allow us to determine when to start Monoclonal Antibody injections for vulnerable children (essentially infants with chronic respiratory pathologies or congenital cardiac pathologies, i.e. approximately 30 children per year in Martinique). The investigators will also be able to anticipate future needs of beds and caregivers to the epidemic to come or in progress. The investigators will therefore have better preventive care for children at risk and better preparation of the healthcare offer.

Research questions