More than 65 million people worldwide are living with long COVID, according to a widely cited estimate published in Nature Reviews Microbiology. That number has likely grown since the paper's publication, given continued waves of reinfection and the emergence of new variants. Six years after the pandemic began, no cure exists. But several treatments are finally moving beyond the anecdotal stage and into controlled trials with measurable results.
What are the most common symptoms?
Fatigue dominates, reported by roughly 58% of long COVID patients. Brain fog or cognitive dysfunction affects about 32%. Post-exertional malaise, where physical or mental activity triggers a disproportionate crash lasting hours to days, appears in an estimated 25-30% of cases. Other frequent symptoms include headaches, sleep disturbances, joint pain, shortness of breath, and dysautonomia (particularly postural orthostatic tachycardia syndrome, or POTS).
Symptoms overlap substantially with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), a condition that existed long before COVID-19 and has affected an estimated 1.3 million Americans with minimal research funding for decades. Long COVID has, somewhat paradoxically, become the largest funding catalyst for post-infectious illness research in history.
What treatments are showing results?
The NIH's RECOVER initiative, funded at $1.15 billion, has been the largest long COVID research program globally. Its pace has drawn criticism from patients and advocacy groups who argue that trials enrolled too slowly and prioritized observational studies over treatment interventions. Still, several findings have emerged.
Low-dose naltrexone (LDN), an off-label use of an opioid antagonist originally approved for addiction treatment, has shown modest improvements in fatigue and cognitive function in small trials. Doses of 1-4.5 mg, far below the standard 50 mg addiction dose, appear to modulate neuroinflammation. A RECOVER platform trial is evaluating LDN alongside other candidates.
Metformin, the common diabetes medication, attracted attention after a June 2023 preprint from the University of Minnesota's COVID-OUT trial found that a 14-day course of metformin taken during acute COVID-19 infection reduced the incidence of long COVID by about 41%. Follow-up data through 10 months confirmed the effect. Metformin costs roughly $4 per month and has a well-established safety profile, making it one of the more promising low-cost interventions.
Paxlovid (nirmatrelvir/ritonavir) for long COVID has produced mixed signals. A Stanford-led study found that a 15-day extended course improved some symptoms in a subset of patients, particularly those with elevated viral persistence markers. But other trials have shown no significant benefit. Patient selection may matter: Paxlovid may help the subgroup with persistent viral reservoirs while doing little for those whose long COVID is driven by autoimmune or neuroinflammatory mechanisms.
Why does this matter for outbreak preparedness?
Long COVID has reshaped how we think about infectious disease impact. Before 2020, pandemic preparedness focused almost exclusively on acute mortality and healthcare system capacity. Post-acute sequelae, the lingering effects that persist weeks to years after the initial infection, received almost no attention in planning frameworks.
That blind spot was expensive. The Brookings Institution estimated in 2022 that long COVID was keeping approximately 2-4 million Americans out of the workforce, with economic costs reaching $3.7 trillion when accounting for lost earnings, medical expenses, and reduced quality of life. Disability applications surged.
Post-acute illness isn't unique to SARS-CoV-2. Post-infectious fatigue syndromes have been documented following Ebola, SARS, MERS, influenza, Epstein-Barr virus, Ross River virus, and Q fever, among others. A 2006 study in Dubbo, Australia followed patients after acute infections with EBV, Ross River virus, and Coxiella burnetii and found that 12% met criteria for chronic fatigue syndrome six months later, regardless of which pathogen caused the original infection.
When the next pandemic-scale pathogen emerges, the acute death toll will again dominate headlines. But the long-tail burden of post-acute illness could rival or exceed it in total impact on society. Vaccination remains the best available tool for reducing long COVID risk. Studies consistently show that vaccinated individuals who experience breakthrough infections develop long COVID at roughly half the rate of unvaccinated individuals, though the risk is not eliminated.
PandemicAlarm tracks acute outbreak data in real time. Understanding that the consequences of any major infectious disease event extend months and years beyond the acute phase is part of reading that data accurately. For more on how acute mortality statistics can mislead, see our CFR vs IFR explainer.