Since it was non-hereditary, how did he contract it? Infection?
No, ALS is not caused by infection. A small number of ALS cases are hereditary (autosomal recessive), but Hawking's case is not one of them. The others represent a disparate group of related but not identical congenital neurodegenerative diseases, which present somewhat differently from each other and which have a variety of known causes (mutations on various genes). These occur in a random manner, and for this reason are called
sporadic ALS. The incidence is increasing world-wide, but the reasons for this are unknown.
Scientists hypothesize that there are environmental factors that predispose individuals to ALS (veterans and some athletes are more than twice as likely to develop ALS as non-veterans/athletes); studies are being done on toxins such as lead, mercury, manganese, radiation, pesticides, but nothing conclusive has so far turned up and the number of individuals in the controlled studies is small..
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