While Noguchi was influential during his lifetime, later research was not able to reproduce many of his claims, including having discovered the causes of polio, rabies, syphilis, trachoma, and yellow fever [REF].
Noguchi's most famous contribution is his identification of the causative agent of syphilis (the bacteria Treponema pallidum) in the brain tissues of patients suffering from partial paralysis due to meningoencephalitis.