What type of symptoms must be reported that may indicate contagious conditions?

The correct choice highlights that diarrhea and fever are significant symptoms that can indicate contagious conditions. These symptoms are often associated with various infectious diseases that can easily spread in communal or workplace settings. For instance, diarrhea can be a symptom of viral infections like norovirus or bacterial infections, while fever might signify an underlying infection that could be contagious, such as influenza. Reporting these symptoms is crucial as it enables timely intervention to prevent outbreaks and protect public health.

Other symptoms such as muscle pain and fatigue, while they can indicate illness, are less definitive indicators of contagious conditions. Similarly, allergic reactions do not generally suggest the presence of infectious diseases that can be transmitted to others. Therefore, recognizing and reporting symptoms like diarrhea and fever is key in managing and controlling infectious disease spread.