Clinical samples. Oropharyngeal samples were obtained by swabbing the back of the throat using sterile cotton swabs (BBL Culture Swabs, Becton Dickinson). On the day of collection, the swabs were transported from the collection site to the processing laboratory at room temperature and then frozen until processed further, as described below. Cognitive testing. All of the participants underwent a battery of cognitive tests, as previously described (45). These included the RBANS (47), Trails A (48), and the Information subtest of the WAIS III (49). Details of these tests are described in SI Materials and Methods.