Distubed neuromuscular transmission in viral infections

14 subjects with influenza or echovirus infection, all suffering myalgia, and 9 subjects with mumps, in whom this symptom was lacking, were investigated with single fibre electromyography (EMG) in the acute phase and during convalescence to reveal a possible disturbance in neuromuscular transmission. In both groups about the same percentage of the potential pairs studied showed abnormal transmission characteristics in the acute phase. Two weeks after the acute infection, this percentage had decreased significantly in the group with myalgia, whilst in the non-myalgia group it was still at the same level. However, on both occasions of investigation and in both groups the percentages were substantially greater than those recorded in healthy individuals. This study demonstrates that acute febrile infections may adversely affect neuromuscular transmission in previously healthy human subjects. The effects observed might offer an explanation to the accentuated muscular weakness in association with infections in patients with an already low safety margion of neuromuscular transmission, e.g. in myasthenia gravis.