When back pain is caused by common muscle strain, it is typically localized and lacks systemic symptoms. However, when back pain appears alongside chills, it signals a deeper, more widespread issue, often involving infection or severe inflammation. Understanding why these two seemingly unrelated symptoms—musculoskeletal pain and a thermal regulation reaction—co-occur is crucial for recognizing a potentially serious health problem. The link between back pain and chills points toward processes affecting internal organs or the spinal structures themselves.
Chills: A Signal of Systemic Response
Chills are a physical manifestation of the body’s attempt to raise its core temperature, usually initiated by the immune system. When the body detects pathogens, it releases chemical messengers that act on the hypothalamus, the brain’s primary temperature control center. These substances “reset” the body’s internal thermostat to a higher target temperature, establishing a fever. Because the actual temperature is below this new set point, the person feels intensely cold. The brain triggers rapid, involuntary muscle contractions (shivering or chills) to generate heat and raise the body temperature. The presence of chills is a reliable indicator of a systemic inflammatory or infectious process, rather than a localized musculoskeletal problem.
Shared Underlying Conditions Causing Both Symptoms
The simultaneous presentation of back pain and chills strongly suggests an infection or inflammatory process affecting a structure near the spine or causing widespread body aches. These underlying causes range from infections of the urinary tract and spine to severe viral illnesses. The pain is usually due to inflammation affecting sensitive tissues or organs located close to the back, not a strained muscle.
Pyelonephritis (Kidney Infection)
One of the most frequent and serious causes is pyelonephritis, a bacterial infection of the kidneys. The kidneys are situated in the flank area of the mid-to-lower back, and when they become inflamed or infected, they cause acute, sharp pain, often high on one side. This pain is accompanied by systemic signs like a high fever and pronounced chills as the body fights the bacterial invasion. Pyelonephritis commonly develops when a lower urinary tract infection ascends to the kidneys. The infection triggers a major immune response, leading to the release of pyrogens that cause the hypothalamic temperature reset and subsequent chills. Urinary symptoms, such as pain during urination, urgency, or cloudy urine, often accompany the back pain and chills.
Spinal Infections
Infections directly involving the spine or its surrounding structures are another concerning cause for this symptom combination. Conditions like a spinal epidural abscess (SEA) or discitis involve a bacterial infection of the disc space or the area between the outer spinal cord membrane and the bone. These infections cause intense, localized back pain that does not improve with rest and worsens over time. The infection triggers a profound systemic reaction, leading to fever and chills. A spinal epidural abscess is particularly concerning because the growing collection of pus can compress the spinal cord or nerve roots, quickly leading to neurological symptoms.
Systemic Viral Illnesses
Generalized systemic illnesses can also produce this dual symptom presentation. Severe viral infections, such as influenza or COVID-19, cause widespread muscle aches (myalgia), often felt intensely in the back. When these infections induce a high fever, the associated chills are a common feature of the body’s temperature regulation efforts. In these cases, the back pain is muscular and generalized, a secondary effect of the body’s inflammatory state, rather than a sign of organ or spinal structure compromise.
When to Seek Urgent Medical Attention
The presence of chills alongside back pain is a serious indicator that necessitates prompt medical evaluation, particularly when accompanied by certain “red flag” symptoms. A sudden onset of severe back pain combined with a high fever, typically above 101°F (38.3°C), warrants immediate care, as this indicates a significant systemic infection.
Any sign of neurological change is an immediate emergency, suggesting possible spinal cord compression from an abscess. These changes include new weakness, numbness, or tingling in the legs or arms, difficulty walking, or loss of control over bladder or bowel function. These neurological deficits indicate pressure on the nerves or spinal cord, and delaying treatment could result in permanent damage.
Other urgent symptoms relate to potential kidney involvement. If back pain and chills are accompanied by signs of a severe kidney infection, such as pain or burning during urination, blood in the urine, nausea, or vomiting, immediate antibiotic therapy is required. This prevents the infection from progressing and spreading bacteria into the bloodstream, a life-threatening condition known as sepsis.