wha-?

I was proofreading a paper for Sara when I came upon this sentence

"He states in the introduction to Secret Judgments of God, that in essence this involves the idea that a disease introduced among populations which never before had experienced the illness, or which had been free from it for so long that any acquired immunity had disappeared, will be attacked in a massive onslaught, with no age group or sex spared infection (Borah 1991: 8)."

what?

by the way- no intro to this sentence- it stands alone in the paper...