Literally. The New York Times absolves him:
When two pre-Columbian individuals died 1,000 years ago, arid
conditions in the region of what is now Peru naturally mummified their
bodies, down to the head lice in their long, braided hair.
This was all scientists needed, they reported Wednesday, to extract well-preserved louse DNA and establish that the parasites had
accompanied their human hosts in the original peopling of the Americas, probably as early as 15,000 years ago. The DNA matched that of the most common type of louse known to exist worldwide, now and before European colonization of the New World.
The findings thus absolve Columbus of responsibility for at least one unintended tragic consequence to the well-being of the people he discovered and called Indians. The Europeans may have introduced diseases, most notably smallpox and measles, but not the most common of lice, as had been suspected.
No, George Bush did!