Cardiac output and cardiac stroke volume may decrease during systemic febrile viral infections. Acute viral respiratory tract infections can affect pulmonary function. For example, research studies have shown respiratory infections to impair pulmonary gas exchange, though the impairment is not serious. Additionally, rhinovirus infection may produce transient peripheral airway abnormalities, which are detected by measuring the dynamic compliance of the lungs and also are not serious. These changes were transient, usually resolving in 2 weeks.
Viral infections can also affect the muscular system.
Some infectious diseases may alter an active person's fluid status. Acute infectious diseases, especially those with gastroenteritis and fever, often result in reduced fluid intake and increased fluid losses. Low levels of body fluid could also affect temperature regulation since less perspiration results in dissipation of less body heat. Impaired fluid status and thermoregulation caused by febrile illness could put an active person in danger of developing heat exhaustion, heatstroke, and circulatory collapse. Because of these effects on the various body systems, acute infectious illness may result in decreased endurance, strength, speed, concentration, or any combination of these factors.