DUOX1 and infection: Thus, the NOX/DUOX enzymes and CD38 conform to other second-messenger-generating enzymes, e.g., phospholipase C, known to be activated via plasma membrane receptors for hormones, paracrine mediators, neurotransmitters, etc. In contrast, SARM1 seems to sense NAD loss, e.g., due to infection by certain viruses, leading to SARM1 activation followed by more NAD degradation, and finally resulting in cell death.