Polyunsaturated fatty acids in multiple sclerosis.

standing of the reporting systems involved. On the one hand there are the cases of "paralytic poliomyelitis" notified by the clinicians to the Department of Health and Social Security.' There may or may not be virus isolates from these patients. Secondly, there are the weekly reports of the virus isolates from diagnostic laboratories.2 The clinical information submitted with these Communicable Disease Reports is necessarily preliminary and the subsequent course of the illness frequently causes revision of the diagnosis. This is verified by the Epidemiological Research Laboratory when these reports are correlated with the official notifications for the annual poliomyelitis surveillance report. The correct figure obtained in this way is included in the annual report of the Department of Health and Social Security and represents the best estimate of the prevalence of poliomyelitis in the community as a whole. In 1965-8 there were 110 cases and in 196972 only 23. Dr Wyatt's larger figure of 39 cases for 1969-72 was obtained by adding the unverified communicable disease reports and overestimates the true position. When these factors are taken into account it is obvious that strains were available from roughly half of the paralysed patients in each period (51/110 and 11/23, respectively) and that my category of "neurological disease" included all the paralytic cases. There are, of course, many defects in a study which depends on an informal arrangement for collection of strains, but it would be very expensive to set up a large prospective study of the question. Moreover, there are no figures available from the prevaccine era for comparison. I would certainly prefer to see available resources devoted to the promotion of polio vaccination. Y COSSART