For centuries, a guiding principle for health care workers (HCWs) has been primum non nocere, or first do no harm. Although this adage has been applied mostly to therapeutic interventions, it also infers that HCWs should not spread infections to their patients, especially the most vulnerable patients. However, HCWs do exactly that when they work with patients while ill themselves with contagious infections. A plethora of evidence suggests that HCWs can transmit a variety of infections to patients during routine clinical activities.1 Even common but untreatable infections like enterovirus and respiratory syncytial virus can prove deadly to immunocompromised patients.2