Record Surge in Tick-Borne Encephalitis Cases in Sweden Linked to Climate Change

Sweden is experiencing an unprecedented increase in tick-borne encephalitis (TBE) cases, with 213 reported by July 20, 2026, marking a sharp rise from 111 cases in the same period of 2024 and 138 in 2025. Health authorities attribute this surge to climate change, which has extended the ticks’ active seasons due to warmer temperatures and earlier springs, thus increasing human exposure to ticks.

According to Ulrika Marking from Folkhälsomyndigheten, the Public Health Agency of Sweden, the climate benefits both ticks and the rodent populations that carry the TBE virus, creating favorable conditions for the spread of the disease. For many infected individuals, TBE may be mild or even asymptomatic; however, severe cases can cause serious neurological complications such as paralysis, personality changes, and loss of consciousness, sometimes resulting in long-term disabilities or death.

In response to the rise in infections, several Swedish regions with high TBE prevalence, including Sörmland, Uppsala, Västmanland, and Östergötland, have implemented subsidized vaccination programs. For example, in Sörmland, vaccinations are free for children aged 3 to 18 years. Despite vaccine availability, Folkhälsomyndigheten currently lacks a national registry to monitor vaccination rates, complicating efforts to evaluate the vaccine's impact across the population.

The increasing number of TBE cases underscores the growing public health challenge posed by climate change as Sweden continues to adapt preventive strategies, including promoting vaccinations in affected areas to curb the spread of this potentially debilitating disease.