Viruses can cause disease in the absence of morphological evidence of cell injury: implication for uncovering new diseases in the future.

A virus can replicate in differentiated cells, thereby altering their ability to make specialized products such as endocrine hormones, neurotransmitters, and lymphokines. Systemically, the outcome can be an imbalance in homeostasis, resulting in diseases of the endocrine, nervous, immune, or other systems, frequently in the absence of detectable cell destruction.