Map of different biotopes and NE distribution in Europe and Western Russia. Temperate broad-leaf forests and boreal forests are the preferred habitats of the Puumala virus rodent reservoir Myodes glareolus, and hence often concur with NE endemic zones, as indicated. However, some regions such as the U.K. have so far no known NE endemicity, despite having broad-leaf forests as an adequate biotope and a documented presence of M. glareolus. The vegetation map was derived from Olson, D. M, E. Dinerstein, E.D. Wikramanayake, N.D. Burgess, G.V.N. Powell, E.C. Underwood, J.A. D'amico, I. Itoua, H.E. Strand, J.C. Morrison, C.J. Loucks, T.F. Allnutt, T.H. Ricketts, Y. Kura, J.F. Lamoreux, W.W.Wettengel, P. Hedao, & K.R. Kassem.