Table 6 Syntactic patterns for propagating event labels to other candidate bacteria-location (or trigger-location) pairs, with examples where B, B1 and B2 are bacteria annotations, and L1 and L2 are location annotations

Nesting

Given the phrase “apple and lettuce surfaces” with its four nested location annotations: apple surfaces, lettuce surfaces, apple, and lettuce, if bacteria B is found to be located in “apple and lettuce surfaces”, we identify four events by associating B with each of the four location mentions, as illustrated in Fig. 4.

Coordination

Given the two coordinated location mentions “tryptic soy broth” and “nutrient broth”, if bacteria B is found to be located in “tryptic soy broth”, we also identify the pair of B and “nutrient broth” as an event, as illustrated in Fig. 4.

Apposition

In the example “[methicillin-resistant Staphylococcus aureus] B1([MRSA] B2)colonization in a [skilled nursing facility] L1([SNF] L2)”, we first identify the intra-clause event B1-L1 using a trigger pattern, and then propagate it to additional three events B2-L1, B2-L2, and B1-L2, based on the apposition relations between B1 and B2 and between L1 and L2, as captured by their syntactic dependencies.

Location hierarchy

Two geographical location mentions are sometimes connected via a comma when they have a clear hierarchical relationship, such as “in [Georgia] L1, [USA] L2” and “residents of [Olmsted Country] L3, [Minnesota] L4”. In this case, we propagate an event relation for a smaller region to that for a larger one.

Participle- preposition

In the example “[Israeli travelers]L1 returning from [Nepal]L2 were diagnosed with [S. Paratyphi A]B1 bacteremia”, we first identify the intra-clause event B1-L1 using a trigger pattern, and then propagate it to B1-L2 through the participle-preposition relation between L1 and L2. This pattern can also be applied to two locations connected by a single preposition such as “in the [Hospital S. Camillo De Lellis]L1of [Roma]L2”.