Map of Switzerland showing (A) sampling units and sampled animals and (B) seropositive animals. Grey shaded areas represent different bioregions, major lakes are in blue. Numbers refer to sampling units: 1) Jura-South, 2) Jura-North, 3) North-West, 4) North-East, 5) Centre-West, 6) Centre-East, 7) South-West, 8) South-Centre, 9) South-East. Colored dots correspond to animals of different species: Orange: roe deer; Red: red deer; Green: chamois; Yellow: ibex. The seropositive chamois (green dot in Figure 1B) located in the unit North-East and indicated by a bright red halo was also positive by PCR. Black areas in Figure 1B refer to communities in which at least one domestic animal was found positive for bovine viral diarrhea virus (persistently infected cattle detected during the summer pasturing season in the frame of the eradication program; data obtained from the Swiss Federal Veterinary Office).