It has been nearly six years since the world first encountered COVID-19, the disease caused by the coronavirus SARS-CoV-2. What began as a mysterious outbreak in early 2020 quickly spiraled into a global pandemic, reshaping societies, economies, and—most enduringly—human health. Today, as researchers dig deeper into the lingering effects of the virus, a clearer, if more complex, picture of long COVID is emerging. The latest findings, highlighted by a sweeping review from Lanzhou University in China and reported by the University of Minnesota’s Center for Infectious Disease Research and Policy (CIDRAP), reveal just how varied and persistent the aftermath of COVID-19 can be.
On January 7, 2026, scientists from Lanzhou University published a meta-analysis that pooled data from 64 studies conducted across 20 countries, encompassing a staggering 2.4 million participants. Their mission? To untangle the web of symptoms that persist long after the acute phase of COVID-19, a constellation of issues now widely referred to as long COVID. According to The Economic Times, the researchers sought to classify long COVID patients by subtypes, focusing on how symptoms clustered together, which organ systems were affected, and what factors might influence the severity or persistence of these symptoms.
So, what did they discover? Fatigue, it turns out, reigns as the most common and stubborn symptom. Whether appearing on its own or alongside joint and muscular pain, cognitive impairment, or shortness of breath, fatigue is the hallmark of long COVID. As CIDRAP noted, these symptoms rarely occur in isolation. "Often, symptoms appear together, such as fatigue with pain, cognitive issues, or shortness of breath," the report explained.
The review went further, grouping patients according to the organ systems most affected. Respiratory symptoms—think persistent cough or difficulty breathing—topped the list, impacting an estimated 47% of long COVID sufferers in the studies reviewed. Neurologic symptoms, such as brain fog or headaches, were reported by 31%, and gastrointestinal symptoms, including nausea and diarrhea, affected 28%. The authors cautioned that these percentages reflect the proportion of patients within the studies, not the general population, but the numbers still paint a sobering picture of the virus’s reach.
Demographic factors also play a crucial role. Women, for instance, are more likely to report fatigue and neuropsychiatric symptoms, while men more often experience respiratory problems. Age is another key factor: older adults are particularly vulnerable to respiratory, cardio-renal, and ear, nose, and throat (ENT) symptoms. These findings echo earlier observations that older people face a higher risk of severe COVID-19 symptoms and complications, including death.
Racial and ethnic disparities have surfaced as well. According to the CIDRAP report, Black and Hispanic participants were more likely to experience respiratory, cardiac, and neuropsychiatric symptoms, whereas White individuals more frequently reported fatigue and musculoskeletal pain. These differences may reflect a complex interplay of genetic, social, and economic factors—reminding us that the pandemic has not affected all communities equally.
Interestingly, the variant of SARS-CoV-2 a person contracted appears to influence their long-term symptoms. The Alpha variant, for example, was strongly associated with loss of smell and respiratory issues, while those infected during the Delta wave reported more ENT-related symptoms. Beyond the virus itself, certain risk factors—such as higher body mass index, socioeconomic deprivation, and preexisting conditions like chronic obstructive pulmonary disease—were linked to a greater risk of cardiopulmonary symptom clusters and an overall heavier long COVID burden.
Despite the breadth of symptoms and the millions affected, one thing is clear: long COVID is rarely confined to a single organ system. As the CIDRAP article emphasized, "The findings show that long COVID rarely affects just one organ system." The researchers behind the review are calling for a more standardized approach to classifying long COVID subtypes, a deeper understanding of the underlying mechanisms, and—crucially—treatments tailored to the specific patterns of symptoms patients experience.
But how does this fit into the broader context of COVID-19? Since its emergence in January 2020, COVID-19 has proven to be a shape-shifting adversary. According to widely cited medical sources, the initial symptoms of COVID-19 can include fever, fatigue, cough, breathing difficulties, and the now-famous loss of smell and taste. These symptoms can appear anywhere from one to fourteen days after exposure. Remarkably, at least a third of those infected never develop noticeable symptoms at all. For those who do, most (about 81%) experience mild to moderate illness, while 14% develop severe symptoms, such as dyspnea or low blood oxygen, and 5% face critical conditions like respiratory failure or multiorgan dysfunction.
Older adults, predictably, face greater risks of severe illness and death. And as the world has learned, some people—regardless of age—continue to suffer a range of effects for months or even years after their initial infection. Organ damage, especially to the lungs, heart, and brain, has been documented, and multi-year studies on the long-term effects are still underway.
The ways in which COVID-19 spreads are, by now, familiar but no less daunting. The virus passes from person to person via infectious particles, which are most easily transmitted when people are in close proximity—especially indoors. Tiny airborne droplets can linger in the air, potentially traveling longer distances, while contaminated surfaces pose an additional, if lesser, risk. People remain contagious for up to 20 days and can spread the virus even if they never develop symptoms, further complicating efforts to control outbreaks.
Testing for COVID-19 relies on molecular techniques such as real-time reverse transcription polymerase chain reaction (RT-PCR), transcription-mediated amplification, and reverse transcription loop-mediated isothermal amplification (RT-LAMP), typically using a nasopharyngeal swab. These tests, along with preventive measures—vaccination, social distancing, mask-wearing, hand hygiene, and improved ventilation—remain the cornerstones of public health efforts. While antiviral drugs have been developed, most treatment still focuses on managing symptoms and providing supportive care.
As the pandemic drags on, the burden of long COVID is becoming impossible to ignore. The Lanzhou University review, backed by the global breadth of its data, underscores the need for targeted research and patient care. The authors urge the medical community to standardize how long COVID is classified, dig deeper into its biological underpinnings, and develop treatments that address the specific needs of different patient subgroups.
For millions around the world, the pandemic’s shadow lingers—not just as a memory, but as a daily reality of fatigue, pain, and uncertainty. The hope is that with continued research and a more nuanced understanding, better support and solutions are on the horizon.