An 88 year old resident of a long term care home has been suffering from a three day onset of increasing shortness of breath and decreased oxygen saturation. At the hospital, an anterior-posterior chest X-ray and sputum culture and sensitivity has confirmed a diagnosis of bacterial pneumonia, yet the client’s tympanic temperature has not exceeded 37.3°C (99.2°F). The health care team would recognize that which of the following phenomena likely underlies this situation?