Inclusion Criteria:
1. Men and woman age 25 and older;
2. Not currently hospitalized
3. Participant self-report of past acute COVID episode with symptom onset and/or initial positive test at least 3 months since initial COVID symptoms and/or test confirming SARS-CoV-2 infection Note: Since some people with long COVID may not have been able to obtain testing during the acute phase of illness, history of a positive COVID-19 test is not required. We will collect data regarding the results of any past COVID-19 testing, but this will not affect eligibility for the trial.
4. Currently symptomatic with self-reported worsening of cognitive function for at least the past 2 months, that could not be better explained by other reasons (i.e. alternative diagnosis or medication changes).
5. Able to provide informed consent.
6. Currently reside in Missouri or Illinois
Exclusion Criteria:
1. Illness severe enough to require hospitalization at the time of starting the study.
2. Unstable medical comorbidities (eg decompensated cirrhosis), per patient report and/or medical records.
3. Immunocompromised from the following: solid organ transplant, BMT, high dose steroids (\>20mg prednisone per day), or tocilizumab
4. Already enrolled in another COVID 19 medication trial (not including vaccination or prophylaxis trials)
5. Unable to provide informed consent
6. Unable to perform the study procedures, including not being a resident of the states of Missouri or Illinois
7. Taking donepezil (rationale: donepezil is a S1R agonist), or sertraline (rationale: sertraline is a strong sigma-1 antagonist).
8. Taking phenytoin (rationale: fluvoxamine inhibits its metabolism), clopidogrel (rationale: fluvoxamine inhibits its metabolism from pro-drug to active drug which raises risk of cardiovascular events), and St John's wort (rationale: fluvoxamine + St John's wort are considered contraindicated because of the risk of serotonin syndrome)
9. Taking SSRIs or SNRIs.
10. Individuals who report they have bipolar disorder or are taking medication for bipolar disorder (lithium, valproate, high-dose antipsychotic), unless the investigator concludes that the risk for mania is unlikely (ie it is doubtful that the patient actually has bipolar disorder).
11. Individuals who take alprazolam or diazepam and are unwilling to cut the medication by 25% (rationale: fluvoxamine modestly inhibits the metabolism of these drugs).
12. Participants taking theophylline, tizanidine, clozapine, or olanzapine (drugs with a narrow therapeutic index that are primarily metabolized by CYP 1A2, which is inhibited by fluvoxamine) will be reviewed with a study investigator and excluded unless the investigator concludes that the risk to the participant is low (this would be unlikely; example: participant takes tizanidine only as needed and is willing to avoid it during study duration).
