The Erve virus is suspected to cause severe headache in humans, lasting several days (thunderclap headache). Mice are characterized as a probable reservoir for the Erve virus. We tested 396 wild mice for Erve virus using an immunofluorescence test and found Erve virus antibodies in five cases, showing that small mammals form a reservoir for Erve virus. If ticks are the vector for the virus, a coincidence with borreliosis should exist. We were unable to confirm this in a homogeneous cohort of 955 young men, 62 of whom tested positive for borreliosis. This group did not test positive significantly more often in the immunofluorescence test than a gender- and age-matched control group.