Fig. 1From: Epidemiological and clinical factors associated with post-exertional malaise severity in patients with myalgic encephalomyelitis/chronic fatigue syndromeThe two-way link between recurrent infections and PEM in ME/CFS patients. An infectious precipitant results in impaired immune function leading to susceptibility to recurrent viral infections and some of ME/CFS manifestations such as fatigue and flu-like symptoms. Stress and mood changes can also impact the immune system. PEM will occur after a stressor (physical, cognitive, emotional and/or infectious) leading to a worsening of ME/CFS baseline symptoms, including immune/inflammatory-related symptoms and psychological disturbances. This will perpetuate the immune dysfunction with aggravation of ME/CFS symptoms, and more frequent viral infections. aME/CFS: myalgic encephalitis/chronic fatigue syndrome. bPEM: post-exertional malaiseBack to article page