Because syndromic surveillance systems use pre-diagnostic data for early detection of disease outbreaks, it is important to know how the earliest signs and symptoms of a disease might appear in these systems. The available medical literature describing the sequence of signs and symptoms of pneumonic plague reveals that, during the earliest stages, patients will most likely present with certain gastrointestinal and minimal, if any, respiratory signs. Without this knowledge, early evidence of pneumonic plague in syndromic surveillance systems may be missed until the respiratory signs become prevalent. Because plague is a zoonotic disease, new syndromic surveillance systems that use animal data from park rangers and veterinarians may provide useful evidence. This paper shows how a review of both human and animal literature can be used to design queries for syndromic surveillance systems.