What is a cluster?

A cluster is defined as at least three cases, occurring within a 7-day period, belonging to the same community or having participated in the same gathering of people, whether they know each other or not. It is an alert characterized by a level of criticality, meaning a level of risk of transmission and impact within a community and of spread throughout the community.

Do not confuse the location of clusters with the mode of transmission

Since May 9, 2020, 4,365 clusters have been reported, involving 50,550 cases. Since May 13, 2020, 638,820 cases have been diagnosed. Thus, the number of cases linked to clusters (excluding close family settings) represents less than 10% of diagnosed cases, due to intense viral circulation that prevents the identification of all clusters. All diagnosed cases are included in contact tracing, whether or not they are identified as part of a cluster.

As of October 12, the locations of clusters currently under investigation, in descending order, are schools and universities (376 clusters), long-term care facilities for the elderly (304), private or public companies (248), healthcare facilities (130), and public or private events bringing people together temporarily (89).

The SI-MONIC system also makes it possible to identify situations at risk of cluster outbreaks and to alert the authorities. It does not describe individual modes of transmission, which are the subject of other upcoming studies.

Preventive measures applied by everyone for the benefit of all

In the absence of a curative treatment or vaccine, and with several major cities under a health-related curfew, it is crucial that everyone adopt preventive measures. These include:

• Adherence to hygiene measures, physical distancing, contact reduction (no hugging, no handshaking, avoiding gatherings), and proper mask-wearing.

• Implementing the “Test-Trace-Protect” strategy: anyone exhibiting symptoms suggestive of COVID-19, even mild ones, must self-isolate, wear a mask, limit contact to the absolute minimum, and get tested as soon as possible.

Limiting gatherings and ventilating enclosed spaces round out these measures, which must be followed by everyone. Protecting yourself also means protecting others.