The clustering of multiple sclerosis in various administrative subunits of western Poland.

A survey of multiple sclerosis was made in the western part of Poland, with special attention being paid to the distribution of the disease in various administrative subunits. The prevalence of MS for the 35 counties (mean 45.08 per 100,000 for definite and possible cases taken together) revealed significant differences between particular regions, with clusters of high prevalence rates occurring in two towns (Leszno, 130,97; Gniezno, 122.83). Local uneven distribution of multiple sclerosis was also found within 198 communes covering the territory of the 35 counties. There were four clusters in eight neighbouring towns and communes with a high prevalence ranging from 74.37 to 141.54, and several with a very low prevalence.