Key Points

Following a gradual increase in COVID-19 cases in early February, the Île-de-France region experienced rapid community spread in March, with the epidemic peaking in week 13, from March 23 to 29. The impact of the epidemic was significant in the Île-de-France region. Residents of the region accounted for approximately 40% of Covid-19 deaths recorded in France since March 1, whether in hospitals or nursing homes.

The lockdown was followed by a sharp decline in the need for COVID-19 care. First observed in outpatient settings during week 14, from March 30 to April 5, and then in hospitals starting April 7, this trend continued through week 24, from June 8 to 14, five weeks after the lockdown was lifted. This downward trend reversed in week 26. Between weeks 27 and 32, most regional epidemiological indicators showed an increase in viral circulation in Île-de-France, particularly in Paris.

In week 35 (August 24–30), the incidence rate continued its exponential growth, reaching 93.3 new cases per 100,000 residents in Île-de-France compared to 65.1 the previous week, and 130 in Paris compared to 90.3 the previous week. The alert threshold (50) has now been exceeded throughout the entire region. The departments of Val-de-Marne and Hauts-de-Seine have also surpassed an incidence rate of 100 cases per 100,000 inhabitants.

The trend in the number of cases and contacts investigated by contact-tracing teams reflects this acceleration in the epidemic’s dynamics in Île-de-France, with a 53% increase in the number of investigations initiated, rising from 5,492 to 8,376 between weeks S34 and S35.

The ratio of contacts investigated per case has been steadily declining since mid-July, falling from an average of 4.8 contacts per investigated case in week 29 to 1.7 in week 35 in Île-de-France.

The 20–30 age group remains the age group most severely affected by the spread of the virus, and the one showing the greatest increase compared to the previous week’s data; however, a significant rise in incidence is also observed in neighboring age groups. Among the oldest age groups (70 and older), the increase remains limited; this situation can be explained by reduced social contacts and better adherence to preventive measures among these individuals. However, the rapid spread of the virus in the rest of the population increases the risk of transmission to older adults and those at risk of severe complications.

The number of new clusters has been increasing since Week 31, with 45 clusters under investigation as of September 2, 22.3% of which are classified as high-risk. Nearly two-thirds of clusters are now emerging in workplaces, social housing and integration facilities, and healthcare settings.

Indicators from community healthcare surveillance networks appear to show an early increase in Covid-19-related activity, while hospital-based indicators do not yet show a comparable rise. However, the fact that clinical indicators lag behind test-based indicators by several weeks requires particular vigilance in the coming days. The impact of the epidemic on community healthcare and hospitals must be monitored as schools and workplaces reopen, leading to increased mixing of people despite the protective measures in place.