The University of Louisville in the United States of America is studying the positive effects of tobacco in the prevention and treatment of Parkinson. It appears that these effects are due to a virus which commonly attacks tobacco and is therefore very common in tobacco leaves:
Similar studies have been summarised in publications by American researchers:
Similar studies also are under way at the University of South Florida
A detailed bibliography of scientific studies in this field has been gathered by an association which supports the rights of smokers in the USA.