A rigor is an episode of shaking or pronounced shivering which can occur with a high fever. It is an extreme reflex response which occurs for a variety of reasons. It should not be ignored, as it is often a marker of significant and sometimes serious infection (most often bacterial). It is important to recognise the patient's description of a rigor and to be aware of the possible significance of this important symptom.
This is a companion discussion topic for the original article at https://patient.info/doctor/rigors-pro