Who infected the chimp?

Dear Editor,

Reuters’ SN Oct 2, 08 news item  reveals scientific findings about the disease HIV which they claim has its origins in Africa and might have been around since the beginning of the 20th century.

What we should note is that Africa was colonized then, but I am curious as to who infected the chimpanzee which they state was the transmitter of the disease.

Yours faithfully,
Name and address supplied