Research suggests that Whole Body Hyperthermia in a sauna-like environment can reduce symptoms related to post-acute sequelae of SARS-CoV-2 (PASC), or Long Covid. The investigators aim to study the feasibility and treatment effect of this procedure for patients experiencing Long Covid symptoms.

This proposed trial will examine, for the first-time, study whole-body hyperthermia (WBH) as a treatment for PASC. The investigators will enroll 21 people with PASC who will be randomized into two conditions with different temperature WBH. The primary aims will explore acceptability and feasibility, reduction of fatigue (primary symptom), and potential mechanisms (inflammation and sleep). Inflammation and sleep have both been shown to be dysregulated in PASC and addressed by WBH in other populations. The investigators will use week 2 as the primary endpoint. However, patients will be followed for 4 and 6 weeks to monitor the duration of effect.

Inclusion Criteria:

1. 18-65 years of age
2. English language proficiency
3. Ability to provide informed consent
4. Ability to lie supine (on back) for 2 hours (required for sauna sessions)
5. Must have had clinically suspected COVID-19 and a positive antibody test or a documented SARS-CoV-2 infection (a positive reverse transcription polymerase chain reaction test) at least 12 weeks prior to Screening (Note: clinician judgment can override lack of positive COVID test with clear Long Covid onset and presentation)
6. The Patient Reported Outcome Measurement Information System Fatigue-Short Form v1.0 -Fatigue 7a (PROMIS F-SF43) raw score of 21 or greater at Screening (onset of fatigue confirmed post-infection as in other studies of PASC)
7. Individuals of childbearing potential must use an acceptable form of birth control.

Exclusion Criteria:

1. Fatigue for known reasons other than PASC (e.g. longstanding diagnosis of Chronic Fatigue Syndrome pre-dating Long Covid, low thyroid, multiple sclerosis, AIDS related fatigue, mononucleosis), as determined by clinical discretion of study investigators
2. Known hypersensitivity to infrared heat exposure, significant history of heat stroke
3. Breastfeeding, pregnancy or planned pregnancy during study
4. Active suicidal intent
5. History of bipolar disorder, psychotic disorders, eating disorders, obsessive compulsive disorder, and/or substance use or dependence (within the last year), as per the Mini-International Neuropsychiatric Interview (MINI)44
6. Positive urine toxicology screen for illicit drug use
7. Any serious unstable medical condition
8. Inability to fit into the sauna device. Morbid obesity (BMI > 40) and/or body shape that might increase the risk of cutaneous burning from the device (because of skin being too close to the heat).
9. Back pain that would interfere with ability to lay on hard surface
10. Using medication that might impact thermoregulatory capacity and cannot be held for an appropriate length (at least one half-life) as determined by clinician judgment prior to receiving WBH treatment
11. Breast Implants
12. Claustrophobia that would interfere with ability to remain in sauna
13. Unsafe cardiac status as defined by abnormal ECG reading at screening visit or as determined by study doctor or subject's physician
14. History of or current diagnosis of thrombosis or thrombophilia
15. History of hemophilia
16. History of febrile seizures or seizure disorders
17. Any new treatments/medications for long-COVID that have started in the past 3 months
18. A subject who in the opinion of the Principal Investigator would not be able to safely complete the study or would jeopardize study integrity.