During the same time that aberrant forms began showing up along the coast of Costa Rica, state Epidemiologists tracked an unknown form of encephalitis along the coast. The encephalitis affected mostly rural farmers, and also people who were around animals and livestock. The encephalitis lasted about three weeks, and the symptoms were headaches, fever, delirium and confusion.
Richard Levine was bitten by a Procompsognathus while on Isla Sorna. When he later expressed concern over the effects, he was told by Sarah Harding that the effects would likely only be a headache, with the effects lasting a week. While the symptoms of his bite are similar to that described for the unknown Encephalitis, there is no concrete evidence to connect the effects of the bite caused by Dx to the mystery Encephalitis on the mainland.
However, an earlier draft of the novel would make this tenuous connection clearer, as it explicitly stated that the mainland Encephalitis was related to the DX.
The Lost World by Michael Crichton page 26-27, 392-393 (First Edition, Thirty Fourth printing)