COVID's Over... So Why Do I Still Have a Fever? | Long COVID

Long COVID, and the Concept of 'Heoyeol' in Korean Traditional Medicine

1. COVID is Over, But I Haven't Recovered Yet

The test result is negative, but my body still feels strange. The thermometer reads around 37 degrees Celsius. It's clearly not high enough to be called a 'fever,' but my body feels hot, my face flushes, and there's a distinct sensation of a slight rise in temperature. Sleep isn't deep, and I get easily tired and fatigued during the day. Especially in the late afternoon, I become sensitive to heat and experience palpitations or a feeling of chest tightness. Can these symptoms simply be dismissed as "not feeling well"?

2. Low-Grade Fever in Long COVID: How Does Modern Medicine Understand It?

According to studies in recent years, persistent inflammatory responses are observed in some patients even after COVID-19. Specifically, a state of 'low-grade inflammation' — a subtle systemic inflammatory state — persists, preventing the immune system from fully stabilizing and leading to dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis. This results in symptoms such as abnormal thermoregulation, chronic fatigue, sleep disorders, and autonomic nervous system dysfunction. The most commonly reported group of conditions is 'Long COVID.' However, this unpleasant sensation of a low-grade fever, which is difficult to quantify, still lacks clear diagnostic criteria in modern medicine.

3. Korean Traditional Medicine Has Long Used the Term 'Heoyeol'

In Korean Traditional Medicine, these symptoms are viewed as "a state where there is heat, but it is not of a 'full' (實, *shi*) nature." Classical physicians referred to this as "Heoyeol" (虛熱, deficiency heat). The term 'Heo' (虛) does not mean 'empty' in a literal sense, but rather signifies a state where the body's balance has collapsed due to the depletion of Jing-qi (精氣, vital essence), Jinyeok (津液, body fluids), and Hyeol (血, blood). For example, in Zhang Zhongjing's *Shanghan Lun* (Treatise on Cold Damage), it states:

“大病之後，虛勞之人，常自汗出，熱不退.”— This refers to a person who is debilitated after a major illness experiencing constant sweating and persistent heat.

Furthermore, Zhu Danxi, in his *Ip-mun*, states:

“虛陽浮越，陰液內損，故身熱而不惡寒.”— This explains that weak Yang energy surges upward, and Yin fluids are damaged, leading to heat without aversion to cold.

This is very similar to what is commonly observed in modern Long COVID patients: "a state where there is a low-grade fever but no sensation of cold, rather an intolerance to heat, accompanied by fatigue."

4. Not Lowering Heat, But Nourishing Yin

In Korean Traditional Medicine, when Heoyeol appears like this, instead of using strong antipyretics or anti-inflammatory drugs, the approach is to restore the body's damaged physiological balance based on the pathologies of "Qi Deficiency Generating Heat" (氣虛生熱, *Giheosaengyeol*) and "Yin Deficiency Generating Internal Heat" (陰虛生內熱, *Eumheosaengnaeyeol*). For example:

• Saengmaeksan (生脈散): Nourishes both Qi and Yin, regulating low-grade fever and spontaneous sweating.
• Jaeumganghwatang (滋陰降火湯): Nourishes Lung Yin and Heart Yin, regulating the phase of body temperature.
• Gamisoyosan (加味逍遙散): Stabilizes the sensation of heat arising from the combination of Liver Heat and Qi stagnation.

These prescriptions are not simply "medicines to lower heat," but rather an approach to diagnose why the body is generating heat and address its root cause.

5. Acupuncture and Respiratory Intervention: Another Answer for Thermoregulation

In addition to herbal medicine, Korean Traditional Medicine believes that acupuncture and breathing exercises help stabilize the autonomic nervous system and restore body temperature rhythm.

• Acupuncture treatment: Points such as Baihui (GV20), Fengchi (GB20), Shenmen (HT7), Neiguan (PC6), and Zusanli (ST36) are involved in autonomic nervous system regulation, and are effectively utilized as regulatory points for Long COVID symptoms accompanied by low-grade fever, fatigue, and insomnia.
• Respiratory intervention: Diaphragmatic breathing or slow inhale-exhale exercises centered on the diaphragm stabilize the respiratory-autonomic nervous system connection in the brainstem, contributing to thermoregulation, improved sleep quality, and fatigue recovery.

6. If You Suspect Long COVID Symptoms, Don't Dismiss Them as Simply a Stamina Issue

A slightly elevated body temperature, unexplained fatigue, and a feeling of emotional instability... To simply attribute all of these to "being in a bad mood" or "weakened stamina" would ignore the numerous cases that already tell us otherwise. What's important is to accurately understand the signals your body is sending, structurally analyze their causes, and design a recovery path. Korean Traditional Medicine has long offered explanations and treatment directions for these symptom clusters through the classical concept of "Heoyeol." Not all persistent low-grade fevers are abnormal. It's important to recognize that after an illness like COVID-19, which deeply depletes the body, recovery can take time. And Korean Traditional Medicine was among the first medical systems to address this 'unrecovered state.' The aftershocks (餘震, *yeojin*) remaining after illness, Heoyeol, and depletion. If we can make these concepts key to recovery, we can shift our focus from merely suppressing heat to restoring overall health.