Feeling an aching back while battling a cold or the flu is a common experience. This discomfort is not a coincidence. Back pain alongside an infection is typically a direct consequence of the body’s internal defense mechanisms or the physical stresses illness places on the musculoskeletal system. Understanding the various causes helps differentiate between a normal, temporary symptom and one that requires medical attention.
Systemic Causes: Immune Response and Inflammation
The primary driver of widespread aches, including back pain, during an illness is the body’s aggressive immune response to a pathogen. When an infection is detected, the immune system releases signaling proteins known as cytokines into the bloodstream. These inflammatory mediators coordinate the fight against the virus or bacteria, but they also communicate with the central nervous system, causing generalized symptoms like fever, fatigue, and pain sensitivity.
These systemic inflammatory chemicals travel throughout the body, triggering a reaction in muscles and joints, which is experienced as myalgia, or muscle aches. The lower back is particularly sensitive to these neuroimmune signals, making the pain more noticeable there. This increased sensitivity means even minor existing back issues can feel significantly worse during a viral infection. This generalized, inflammatory pain usually subsides completely once the underlying infection has cleared and the immune response calms down.
Mechanical Stressors and Muscle Strain
Physical actions and changes in behavior while sick can directly strain the back’s muscles and ligaments. Violent and persistent coughing or sneezing, common with respiratory illnesses, forcefully contracts the core and intercostal muscles. This repeated, sharp exertion can lead to acute muscle soreness in the thoracic and lumbar regions.
Changes in posture and activity levels contribute significantly to pain. When unwell, people often spend extended periods resting or lying down in unsupportive positions that stress the spine. This prolonged lack of movement and poor positioning can lead to muscle stiffness and “bed rest back pain.” Episodes of fever and chills also cause muscles to tense and contract involuntarily, increasing overall muscle tension felt in the back.
Localized Pain from Organ Involvement
While most back pain with an illness is generalized, sharp or localized back pain can signal that the infection has settled in a specific organ. The most common example is a kidney infection, medically known as pyelonephritis, which often develops from an untreated urinary tract infection (UTI). Since the kidneys are situated in the back of the abdominal area, an infection causes a distinct, localized pain.
This pain is typically felt in the flank—the area between the lower ribs and the hips—and may be present on one side or both. Unlike the diffuse ache from systemic inflammation, kidney pain is often accompanied by other specific symptoms, including a high fever, chills, nausea, and changes in urination. These changes can include a burning sensation when urinating, frequent or urgent need to go, or cloudy and foul-smelling urine. If back pain is sharp, localized to the flank, and paired with these urinary or severe systemic symptoms, it requires immediate medical evaluation to prevent serious complications.
Short-Term Relief and Medical Consultation
For the generalized back pain caused by inflammation and muscle strain, several short-term strategies can provide relief while the body fights the illness. Over-the-counter non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen can help reduce both the systemic inflammation and the pain. Applying heat, such as a heating pad or warm compress, can relax tense back muscles, while cold therapy may be more useful for reducing sharp, localized inflammation. Gentle movement and avoiding prolonged bed rest, like short walks or simple stretches, can prevent stiffness without overexerting the body.
Some symptoms are considered red flags and require immediate medical attention to rule out a more serious condition. Seek urgent care if your back pain is accompanied by:
- A very high fever.
- Severe localized pain in the flank.
- Difficulty urinating.
- Numbness or tingling in the legs or groin.
- Loss of bowel or bladder control, which is an urgent neurological emergency.
Back pain that does not improve after the primary illness has resolved or pain that is severe and unrelenting should also prompt a consultation with a healthcare provider.