2024 Highlights
- Minnesota continues to be in the top 10 states nationwide for incidence of tickborne diseases like Lyme disease, anaplasmosis, and babesiosis. Powassan virus cases reached a new record in 2024, with 14 cases reported.
- It was a moderate year for mosquito-borne arboviral diseases, with 35 cases of West Nile virus, four cases of Jamestown Canyon virus, and one case of La Crosse encephalitis reported.
- The most common travel-associated vectorborne disease in Minnesota is malaria, and MDH reported a record 90 cases for 2023.
Although Minnesota reports cases of both tickborne and mosquito-borne diseases every year, tickborne diseases are much more common. Lyme disease continues to be the most frequently reported, followed by anaplasmosis and babesiosis. In 2022, a new case definition for Lyme disease was implemented nationally, allowing Minnesota to count cases based on lab reports alone. As a result of this change case counts increased compared to previous years, but the number of reports received each year has stayed consistent. Cases of anaplasmosis were up to 627 reported cases in 2024, continuing a trend of increasing cases that began in the mid-2010s. Babesiosis is less commonly reported than either Lyme disease or anaplasmosis, but in 2024, Minnesota again reported a record number of cases (89), surpassing the previous high of 73 cases in 2023.
Arboviruses can be transmitted by mosquitoes or ticks, and in Minnesota, the most commonly reported arboviral infections are West Nile virus (transmitted by mosquitoes) and Powassan virus (transmitted by ticks). Activity for some arboviruses, like West Nile virus, was lower in 2024, with just 35 cases reported, along with an additional seven people that tested positive after donating blood. These reports in blood donors help us track disease activity across the state, as many people that are infected with West Nile Virus never develop symptoms. Similar to recent years, there were four cases of Jamestown Canyon virus and a single case of La Crosse encephalitis. Both Jamestown Canyon virus and La Crosse encephalitis are transmitted by mosquitoes and are much less common than West Nile. On the tickborne side, 2024 was a record year for Powassan virus. Fourteen cases were reported, surpassing the previous high of 11 cases from 2011. Three cases of Powassan and one case of West Nile virus died as a result of their illness.
Malaria is the most common travel-associated vectorborne disease reported in Minnesota, and there were 84 cases in 2024. People reported exposures in 27 countries around the world, with the majority of cases (87%) reporting exposure in Africa. In addition to malaria, the global outbreak of dengue in 2024 resulted in a record-high case count of 46. Most were not severe, and travel to 16 countries was reported. Minnesota also reported eight cases of chikungunya virus in 2024.
