Why does a viral cold cause fever?

Generally, the main causes of fever caused by viral colds include viral invasion activating the immune response, cytokines acting on the body's thermoregulatory center, increased heat production and reduced heat dissipation, direct viral effects on cellular function and metabolism, and the combined effects of inflammatory response and systemic stress. If symptoms occur, it is recommended to seek timely medical treatment at a qualified hospital. Detailed explanations are as follows:

1. Viral Invasion Activates the Immune Response

When viruses enter the human body, they invade host cells through the respiratory mucosa and replicate within these cells. The body's immune system identifies these foreign viral antigens and initiates both innate and adaptive immune responses. For example, viral nucleic acids or surface proteins are recognized by pattern recognition receptors of host cells, triggering a series of signaling pathways that prompt immune cells to release cytokines, which are key substances in inducing fever.

2. Cytokines Act on the Thermoregulatory Center

After recognizing the virus, immune cells secrete various cytokines such as interleukin-1, tumor necrosis factor-alpha, and interferon. These cytokines can reach the hypothalamic thermoregulatory center through the circulatory system. The hypothalamus functions as the body's "thermostat," normally maintaining body temperature within a relatively stable range. However, cytokines act on hypothalamic neurons, resetting the thermoregulatory set point—for example, raising it from 37°C to 38°C or even higher—thereby causing fever.

3. Increased Heat Production and Reduced Heat Dissipation

Once the thermoregulatory set point is elevated, the body employs various physiological responses to increase heat production and reduce heat dissipation to reach the new "set temperature." In terms of heat production, skeletal muscles contract involuntarily, generating additional heat. Meanwhile, the body's metabolic rate increases, leading to higher heat production from organs such as the liver. Regarding heat dissipation, skin blood vessels constrict, reducing blood flow to the body surface and lowering heat dissipation efficiency, causing the body temperature to rise and remain at the set point level.

4. Direct Viral Effects on Cellular Function and Metabolism

Some viruses not only utilize cellular resources for replication after infecting cells but may also directly affect normal cellular function and metabolism. For example, viruses might interfere with intracellular energy metabolic pathways, leading to abnormal heat production, or disrupt temperature regulation mechanisms within cells, thereby disturbing the balance between heat production and dissipation. Additionally, cellular damage and death caused by viral infection can release endogenous pyrogenic substances, further intensifying the febrile response.

5. Combined Effects of Inflammatory Response and Systemic Stress

A viral cold can trigger an inflammatory response in the respiratory mucosa, where the release of local inflammatory factors not only causes symptoms such as nasal congestion and runny nose but may also affect the whole body through the circulatory system. At the same time, the body experiences a state of stress when fighting viral infection; stress responses such as sympathetic nervous system activation and increased adrenal cortical hormone secretion also affect thermoregulation, collectively contributing to the occurrence of fever. The combined effects of systemic inflammation and stress make fever a common symptom of viral colds.

Patients with viral colds can follow medical advice to use medications such as Ganmaoling Granules, antiviral oral liquid, and Pudilan Xiaoyan Oral Liquid. Additionally, maintaining good personal hygiene habits, such as frequent hand washing and wearing masks, can help reduce the risk of virus transmission and infection.