Body aches are a common symptom associated with COVID-19. This soreness can significantly impact daily life, ranging from mild discomfort to severe pain that limits mobility. Understanding the biological processes that cause these aches clarifies why they are a common part of the illness.
How the Immune System Responds to the Virus
When the SARS-CoV-2 virus enters the body, the immune system detects it. This initial detection triggers an immediate, non-specific defense known as the innate immune response. The virus uses its spike protein to attach to and enter host cells, primarily through the angiotensin-converting enzyme 2 (ACE2) receptor found on various cell surfaces.
Once inside the cells, immune cells recognize the virus and begin to mount a defense. This early activation involves sending out signals to prepare the body to fight the infection. These signals aim to clear the virus and prevent further spread.
The Role of Inflammation and Cytokines
The immune system’s fight against the SARS-CoV-2 virus leads to a widespread inflammatory response. This response is mediated by signaling molecules called cytokines, which are small proteins released by immune cells. These cytokines act as messengers, coordinating the body’s defense mechanisms.
While cytokines are necessary for combating the infection, their overproduction can lead to systemic inflammation. Pro-inflammatory cytokines, such as interleukin-6 (IL-6), interleukin-1 (IL-1), and tumor necrosis factor-alpha (TNF-α), are released in increased amounts during a COVID-19 infection. This generalized inflammatory state is a primary driver of the ache sensation experienced by many individuals. The immune response, while protective, can inadvertently cause discomfort as it works to eliminate the pathogen.
Why Muscles and Joints Ache
The systemic inflammation caused by the activated immune response directly translates into pain felt in muscles and joints. Inflammatory chemicals, including cytokines and various immune cells, can infiltrate muscle tissue, joint capsules, and connective tissues. This infiltration leads to a localized inflammatory reaction within these areas.
The presence of these inflammatory mediators irritates nerve endings in muscle fibers and around joints. This irritation sends pain signals to the brain, resulting in widespread soreness, stiffness, and aching. This type of pain, known as myalgia for muscle pain and arthralgia for joint pain, is a common feature of many viral infections, including influenza. The pain can manifest as a dull ache and may limit mobility.
How Fever Intensifies Body Aches
Fever is an immune response to infection that directly contributes to the intensity of body aches during COVID-19. When the body’s core temperature rises, it is an adaptive mechanism aimed at creating an unfavorable environment for the virus. This elevated temperature can directly exacerbate muscle soreness and contribute to a generalized feeling of malaise.
The physiological processes involved in fever also place additional strain on the muscles. For instance, the body’s attempts to regulate its temperature, such as shivering to generate heat or sweating to cool down, involve muscle contractions and activity. These efforts can further tax already inflamed or fatigued muscles, intensifying the overall feeling of aches and discomfort.