1. 1. Cook, S. D. & Dowling, P. C. Neurology 30, 80–91 (1980). 2. Ter Meulen, V. & Stephenson, J. R. in Multiple Sclerosis (eds Hallpike, J. F., Adams, C. W. M. & Tourtellotte, W.) 241–274 (Chapman and Hall, London, 1983). 3. Kaprowski, H. et al. Nature 318, 154–160 (1985). 4. Mauser, S. L. et al. Nature 322, 176–177 (1986). 5. Karpas, A., Kampf, U., Siden, A., Koch, M. & Poser, S. Nature 322, 177–178 (1986). 6. Hull, R. N., Minner, I. R. & Smith, J. W. Am. J. Hyg. 63, 204–215 (1956). 7. Hsuing, G. D. Prog. med. Virol. 14, 241–247 (1972). 8. Robbins, S. J., Wrzos, H., Kline, A. L., Tenser, R. B. & Rapp, F. J. infect. Dis. 143, 396–402 (1981). 9. Mitchell, D. N. et al. Lancet ii, 387–391 (1978). 10. Goswami, K. K. A. & Russell, W. C. /. gen. Virol 60, 177–183 (1982). 11. Goswami, K. K. A. & Russell, W. C. /. gen. Virol. 64, 1663–1672 (1983). 12. Goswami, K. K. A., Lange, L. S., Mitchell, D. N., Cameron, K. R. & Russell, W. C. /. gen. Virol. 65, 1295–1303 (1984). 13. Goswami, K. K. A., Cameron, K. R., Russell, W. C., Lange, L. S. & Mitchell, D. N. /. gen. Virol. 65, 1881–1888 (1984). 14. Salmi, A., Reunanan, M., Ilonen, J. & Panelius, M. Clin. exp. Immun. 52, 241–149 (1983). 15. Norrby, E. et al. Infect. Immun. 10, 688–694 (1974). 16. Strangaitis, S. M., Shapshak, P., Tourtellotte, W. W., Lee, M. M. & Reiber, H. O. Electro–phoresis 6, 287–291 (1985). 17. Vandvik, B. et al. J. Neurol. 231, 307–312 (1985). 18. Nordal, H. J. et al. Scand. J. Immun. 7, 381–386 (1978). 19. Vandvik, B., Norrby, E., Nordal, H. J. & Degro, M. Scand. J. Immun. 5, 979–992 (1976). 20. Pringle, C. R. in Molecular Basis of Virus Disease. S.G.M. Symposium 40 (eds Russell, W. C. & Almond, J.). (Cambridge University Press, in the press). 21. Goswami, K. K. A., Morris, R. J., Rastogi, S. C., Lange, L. S. & Russell, W. C. J. Neuroimmun. 9, 99–108 (1985). 22. Chow, C.–H. J. et al. Neurology 33, 24–28 (1983). 23. Russell, W. C. in Immunology of Nervous System Infections, Progress in Brain Research 59 (eds Behan, P. O., ter Meulen, V. & Clifford Rose, F.) (Elsevier, London, 1983). 24. Cornwell, H. I. C., McCandish, I. A. P., Thompson, H., Laird, H. M. & Wright, N. G. Vet. Rec. 98, 301–303 (1976). 25. Russell, W. C., Patel, G., Precious, B., Sharp, I. & Gardner, P. S. /. gen. Virol. 56, 393–408 (1981). 26. Russell, W. C., Newman, C. & Williamson, D. H. Nature 253, 461–462 (1975).