If conference organizers/event planners were notified that an individual who attended the event are ill/symptomatic, they should notify attendees who were close contacts with the ill person (or organizers may notify the local health department who will then notify attendees). A close contact is someone who was in close proximity of the ill individuals (6 feet), for a prolonged period of time. This may include sitting and dining at a shared booth/table or had direct contact with infectious secretions of an ill person (e.g., being coughed on).
If a person who was at a large gathering/event begins to show symptoms, they should self-monitor themselves for symptoms for 14 days and contact their healthcare provider. If you notice that you have symptoms and feel that you need to be medically evaluated, contact your health care provider and stay home/do not go to public gatherings, work/school.