Lyme disease is a bacterial infection transmitted by bites from infected ticks commonly found in much of North America and Europe. Initial symptoms of infection include the characteristic “bullseye” rash and fever, fatigue, and headaches, which can occur anywhere from three days to a month after being bitten. With treatment, most cases of Lyme disease are curable. If not treated, however, infection can spread to the joints, heart, and brain, and can cause severe pain, headaches, nerve pain and dysfunction, and inflammation of the brain and spinal cord. In a new study by Ilona Suhanda and colleagues, published in Nature Scientific Reports in May 2025, the surveillance of Lyme disease diagnosed incidence in France was investigated. Surprisingly, they found rates of Lyme disease much higher than official numbers.
This study explored how surveillance through a computerised decision support system with high participation from general practitioners (GPs) country-wide compared to France’s national Sentinelles network. The new decision support system, Antibioclic, assists GPs with antibiotic prescription recommendations for many health conditions, including Lyme disease. Records were used to investigate the diagnosed incidence of Lyme disease across France and compared to the national reporting through the Sentinelles network, the current standard for mandatory reporting. This study found a diagnosed incidence of Lyme disease nearly five times higher than the Sentinelles network across the five years of the study. The spatial distribution of cases, however, was well-aligned with the Sentinelles network, suggesting the underlying epidemiology of Lyme disease being measured is similar.
GlobalData epidemiologists use nationally representative studies of diagnosed incidence with internationally consistent case definitions to calculate case numbers across markets, and as a result, utilise Sentinelle data in France. Based on this source, GlobalData epidemiologists forecast that case numbers for Lyme disease will increase by 0.2% from 2025 to 2034, reaching nearly 58,000 newly diagnosed incident cases per year. The estimate by Suhanda and colleagues is nearly five times higher than this estimation, prompting a closer look at the methodology.
The most likely cause for the difference in diagnosed incidence of Lyme disease is case definition differences. This study uses a much wider case definition for Lyme disease, with either a tick bite, suspected infection, or positive serology (the national definition for a confirmed case in France and all other Lyme-endemic countries) considered sufficient for a case of Lyme disease. This, along with potential selection bias introduced by only 50% of GP practices in France being enrolled in this service, which potentially see more Lyme cases than other GPs, may result in a higher estimate than national sources. Additionally, because positive serology is required for a case recognised by the national system, the national system may truly undercount cases that are tested too early to detect Lyme disease or cases that are treated without official testing. Regardless of the cause, this study shines a light on the potential undercounting of Lyme disease cases in France and suggests more investigation of this important disease is needed to ensure adequate resources are allocated to education, prevention, and treatment of the disease.
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By GlobalData