Exercise stress increases susceptibility to influenza infection

Area of Science:

• Immunology
• Exercise Physiology
• Virology

Background:

• Severe exercise stress is linked to increased upper respiratory tract infection (URTI) risk.
• While moderate exercise may decrease URTI risk, evidence on stressful exercise and influenza susceptibility is limited.

Purpose of the Study:

• To investigate the impact of stressful exercise on susceptibility to influenza virus infection.
• To determine if severe exercise stress alters morbidity, symptom severity, and mortality in a mouse model of influenza.

Main Methods:

• Mice were subjected to treadmill running to volitional fatigue for three consecutive days (exercise group) or rested (control group).
• Following the final session, mice were intranasally inoculated with influenza virus (A/Puerto Rico/8/34).
• Morbidity, symptom severity, and mortality were monitored daily for 21 days.

Main Results:

• Exercise stress significantly increased susceptibility to influenza virus infection.
• The exercise group exhibited higher morbidity, greater symptom severity, and increased mortality compared to controls.
• These effects were particularly noted on days 6 and 7 post-infection (P<0.05).

Conclusions:

• Severe exercise stress enhances susceptibility to influenza virus infection in mice.
• These findings support the hypothesis that strenuous physical exertion can increase vulnerability to respiratory viral infections.
• The study highlights the potential negative impact of intense exercise on the immune system's response to influenza.