Final answer:
Chlamydia trachomatis is the condition among the listed options that is considered a nationally notifiable infectious disease, which must be reported to the CDC.
Step-by-step explanation:
Among the four conditions listed - Respiratory syncytial virus (RSV), Methicillin-resistant Staphylococcus aureus (MRSA), Clostridium difficile, and Chlamydia trachomatis - Chlamydia trachomatis is considered a nationally notifiable infectious disease. The Centers for Disease Control and Prevention (CDC) includes Chlamydia trachomatis infections in the National Notifiable Diseases Surveillance System (NNDSS), requiring healthcare providers to report each diagnosis to the CDC. This reporting system helps in tracking the prevalence and spread of significant public health concerns, including sexually transmitted infections (STIs) like chlamydia.