When the influenza virus enters the body, it triggers an immune response that leads to inflammation. This process is what causes the characteristic flu symptoms, including muscle and joint aches.

Inflammation can also affect the nerves in the body, making them more sensitive to pain. This can make the muscle and joint aches feel more intense and uncomfortable. The combination of inflammation and increased nerve sensitivity is what makes the flu feel so achy and miserable.

Understanding the role of inflammation in flu symptoms can help explain why over-the-counter pain relievers, which reduce inflammation, can help alleviate some of the discomfort. Additionally, this knowledge can inform the development of new treatments for the flu that target the inflammatory response itself.