Viruses that cause recurring outbreaks

Influenza viruses and other respiratory viruses such as RSV follow a seasonal pattern, with influenza and bronchiolitis outbreaks generally occurring each year between October and March. SARS-CoV-2, the virus causing COVID-19, does not currently appear to follow a distinct seasonal pattern, with waves observed throughout the year; however, the winter season may facilitate its spread. The simultaneous circulation of these different viruses can pose a significant challenge for the healthcare system.

A surveillance system established by Santé publique France

As part of its surveillance missions, Santé publique France has established a system that includes monitoring of viral acute respiratory infections (ARIs) responsible for epidemics. The goal of this system is to provide a coherent overview that allows for the assessment of the impact of ARIs on healthcare provision, their burden on public health, and the portion that is preventable through measures such as vaccination.

This surveillance involves continuous monitoring of the epidemiology of ARIs in the French population, and more specifically of the main respiratory diseases, whether in primary care, in long-term care facilities, in hospitals, and in terms of mortality. Influenza, COVID-19, bronchiolitis, and other RSV infections are the conditions specifically monitored under this surveillance program, both clinically and syndromically as well as virologically.

During periods of higher circulation (October through March), weekly surveillance data are summarized in the ARI bulletin.

• Access the ARI epidemiological bulletins

At-risk populations

The characteristics of populations vulnerable to these infections depend on the virus. For SARS-CoV-2 (COVID-19), as well as for influenza viruses and RSV, people over 65 years of age, immunocompromised individuals, pregnant women, and people with comorbidities are more susceptible to complications following infection.

Children under 1 year of age are also particularly at risk for RSV infections (bronchiolitis).

Possible Prevention

To prevent these outbreaks, adopting preventive measures is recommended, particularly wearing a mask as soon as symptoms appear in crowded places and in the presence of vulnerable individuals, handwashing, and regularly ventilating enclosed spaces. These measures are an effective way to protect against respiratory infections and their complications by limiting the risk of transmitting these viruses to others, especially those at risk.

In addition, COVID-19, influenza, and RSV infections are vaccine-preventable diseases. Vaccination is the best means of protection against severe forms of COVID-19 and influenza. Monoclonal antibodies are also available for the prevention of RSV infections in infants.