2000 might be when the disease peaked. It mentions in the passage that the government started to ban farmers from feeding their livestock high risk meat, and that the disease peaked shortly after that. Since 2000 is 'shortly after' 1997, the source from 2000 might be from the peak.
The answer to your question is gets
There has to be a specific subject, say if it was an English writer, they'll need to gather context clues to lead to an answer
