Your primary dx should be the sign/symptom or diagnosis that drove the encounter. This may or may not be the presenting problem. (ie pt presents with pharyngitis, but due to pain has not been drinking fluids. Labs indicate dehydration, for which an IV of fluids is started and he/she is admitted overnight.
Neurosyphilis is considered infectious but is not transmitted from person to person. Generally, a disease like this is caused by an infectious agent and not spread between people. Neurosyphilis, although infectious, is not a genetic disease. It is not caused by a defective or abnormal gene.
Contagious Disease Causes, Contagious Disease List, Types of Contagious Diseases. A disease is contagious if it caused by some type of infecting organism that is spread human to human. Not all diseases involve an organism and not all organism involved diseases are transmitted person to person. Disease means impairment of your health.