National Surveillance: Key Findings for 2020 in Metropolitan France

In primary care

• An estimated 25,000 to 68,530 cases of Lyme disease diagnosed annually between 2009 and 2020.

• An upward trend in the estimated annual number of cases since 2009.

• The annual incidence rate of Lyme disease was estimated at 91 cases per 100,000 inhabitants (60,033 estimated cases) in 2020, compared to 76 cases per 100,000 inhabitants (50,133 estimated cases) in 2019. Since 2009, it has fluctuated between a low of 41 in 2011 and a high of 104 in 2018.

In the hospital

• In 2020, 710 cases of Lyme borreliosis were hospitalized in France. Since 2005, the annual number of hospitalized cases diagnosed with Lyme borreliosis has fluctuated between 649 in 2005 and 990 in 2017, with an average of 842 hospitalized cases per year.

• The incidence rate of these hospitalizations fluctuated between 1.1 (2005 and 2020) and 1.5 per 100,000 inhabitants (2011 and 2017), with a statistically significant upward trend during the 2005–2019 period. In 2020, it was 1.1 per 100,000 inhabitants. This decrease in incidence in 2020 should be interpreted with caution due to the possible impact of the COVID-19 pandemic on hospital utilization.

• Hospitalizations for Lyme disease are more common between June and October.

• The age groups most affected are children aged 5 to 9 and adults aged 70 to 79.

• About half of hospitalized cases are associated with neurological symptoms (neuroborreliosis).

• The annual incidence of hospitalizations for neuroborreliosis has remained stable since 2005 (between 0.5/100,000 inhabitants and 0.8/100,000). In 2020, it was 0.6/100,000 inhabitants.

Significant regional variation in incidence rates

The data show significant regional variation in incidence rates of cases diagnosed in private practice:

• The eastern and central regions of mainland France (notably Alsace, Lorraine, and Limousin) have high annual incidence rates (over 100 cases per 100,000 inhabitants);

• The western regions and the southeastern Mediterranean region have lower annual incidence rates (less than 50 per 100,000 inhabitants).

The same pattern is observed for hospitalizations, with higher annual incidence rates of hospitalization for Lyme disease (>2 cases per 100,000) in eastern and central France.