Determining the Nature of an Illness

In the quiet town of Eldridge, a mysterious illness began to spread among the residents. Initially, only a few reported symptoms like fatigue and fever, but soon, the number of cases began to rise alarmingly. The local doctor, Dr. Foster, was particularly concerned and decided to investigate the situation thoroughly. She noted that many of the affected individuals had been at the same public event just days prior, leading her to suspect that the illness was __________.