Why does COVID-19 affect so many different body systems?

Science · Published 9 October 2026 Swipe more like this →

In short: While many respiratory viruses target the lungs, COVID-19 can cause a vast array of symptoms, from loss of taste to fatigue. Scientists believe the virus's ability to hijack the ACE2 receptor allows it to spread far beyond the respiratory tract, impacting multiple organs and systems.

The diversity of COVID-19 symptoms—including fever, cough, body aches, and even neurological issues—remains a complex puzzle. Scientists have not yet fully determined why different people experience such vastly different symptoms. However, they do understand the mechanisms behind specific issues. For instance, shortness of breath occurs when the virus or the immune system damages lung tissue, causing the alveoli—the tiny air sacs responsible for gas exchange—to swell or fill with fluid. This respiratory distress can occur when the body's inflammatory response causes lung tissue to become swollen. Such complications can lead to serious outcomes like lasting damage to the heart muscle.

The unique loss of smell and taste is linked to the virus damaging specific cells in the nose that transmit odor signals to the brain. While this was a hallmark of early cases, studies suggest this symptom is less common with the Omicron variant. Other symptoms, like fatigue, are harder to pin down; they may stem from direct cell damage, respiratory issues like pneumonia, or the sheer exhaustion of the immune system fighting the infection.

The virus, SARS-CoV-2, emerged in December 2019 and can lead to severe complications such as respiratory failure, kidney failure, or even death. While many experience mild illness or no symptoms at all, others face 'long COVID-19,' where symptoms like weakness or changes in sense persist for months. The ability of the virus to cause such widespread systemic effects is largely attributed to the ACE2 receptor, which acts as a gateway for the virus into various cells.

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