Shaking or involuntary movements during or after a COVID-19 infection can range from familiar chills associated with a fever to complex, persistent neurological tremors that develop weeks or months later. Understanding the different origins of this physical symptom is important, as the cause determines the necessary response and treatment. The mechanisms involve the body’s general immune response to acute illness and longer-term impacts on the nervous system.
Shaking Caused by Acute Infection and Fever
The most common form of shaking experienced during the acute phase of COVID-19 is known as rigor, or fever shakes. This is not a neurological disorder but a deliberate physiological response orchestrated by the body’s temperature regulation system. When the immune system detects the virus, it releases inflammatory signaling molecules called pyrogens, which raise the body’s internal temperature set point.
To reach this new, higher set point, the body initiates involuntary muscle contractions, or shivering, which rapidly generates heat. Blood flow shifts from the extremities toward the core, helping to preserve the heat being created by the muscles. These episodes typically subside as the fever is controlled or as the acute infection begins to resolve.
Neurological Mechanisms Behind Persistent Tremors
Shaking that persists long after the acute infection has passed points to neurological or systemic issues related to Long COVID. This type of involuntary movement is differentiated from fever-related chills because it is not tied to temperature changes and can last for extended periods. A frequently reported symptom is “internal tremor” or “internal vibrations,” a sensation of shaking felt intensely by the patient but often invisible to an observer.
A primary mechanism behind these persistent symptoms is dysautonomia, a dysfunction of the autonomic nervous system (ANS) that regulates involuntary bodily functions. The viral infection or resulting inflammation can disrupt the ANS, leading to Postural Orthostatic Tachycardia Syndrome (POTS). This condition involves sympathetic nervous system overactivity, sometimes described as an adrenergic storm, where the body produces excessive stress hormones. This over-activation can manifest as a noticeable or internal tremor, along with symptoms like dizziness, rapid heart rate, and fatigue, especially when standing upright.
The persistent tremors may also be linked to small fiber neuropathy (SFN), which involves damage to the small nerves that control sensory and autonomic functions. SFN is often found in patients reporting internal tremors and POTS following a COVID-19 infection. Furthermore, inflammatory impact on the central nervous system may be at play, as the widespread inflammation triggered by the virus can affect motor control centers in the brain, such as the cerebellum. While direct viral invasion is possible, immune-mediated responses, where the body’s defense system mistakenly attacks healthy nerve tissue, are widely considered factors in these neurological issues.
Identifying When Shaking Requires Medical Attention
While mild, transient shaking during a fever is a normal part of the immune response, other forms of shaking warrant a medical evaluation. You should consult a healthcare provider if the shaking is severe, localized to one side of the body, or significantly interferes with daily tasks like eating or writing. Tremors that start suddenly and are accompanied by other new neurological deficits require attention.
Warning signs that require prompt medical attention include uncontrolled shivering or shaking that lasts for more than an hour or two despite fever management. Confusion, slurred speech, sudden weakness, or difficulty walking alongside the shaking are concerning symptoms. A medical professional can perform tests to differentiate between post-infectious neurological conditions like POTS or SFN and other potential causes, such as medication side effects or electrolyte imbalances.