The Centers for Disease Control and Prevention recently released data showing that nearly one in five people experience symptoms of Covid more than three months after their initial infection, adding to an array of studies that struggle to pinpoint exact rates of long Covid in the U.S. population. Most studies have placed the rate somewhere between 10% and 25% of all people infected with the virus.

Since the first reports of long Covid in 2020, cognitive dysfunction and “brain fog” have been considered to be commonly agreed-upon symptoms. But how the virus interferes with brain function is still mainly a mystery. Recent research, however, is shedding light on what may trigger these symptoms and how these processes may relate to other neurodegenerative diseases.

NICHOLAS REYNOLDS; nicholas.reynolds@latrobe.edu.au 
    Reynolds is a fellow at the La Trobe Institute for Molecular Science and the co-author of an article on neurological symptoms of Covid-19, published in Nature Connections.

Reynolds’ article notes that although neurological symptoms are reported in many cases of Covid-19, researchers do not understand “the molecular mechanisms triggering… neurological symptoms.” The effects of the virus share some features of neurodegenerative diseases. Reynolds’ team identified two peptides among those expressed by the SARS-Co-V-2 virus that assemble into amyloids that are toxic to neuronal cells in the brain.

Reynolds told the Institute for Public Accuracy today that the virus “readily form[s] aggregated protein clumps that look very similar to amyloid deposits seen in the brains of people with neurodegenerative diseases such as Alzheimer’s and Parkinson’s. But much more work needs to be done to see if these amyloid deposits are detected in tissue samples or bodily fluids from Covid positive people.”

Reynolds’ team noted that “some of the ‘brain-fog’ type symptoms are similar to some early symptoms of Alzheimer’s disease. Amyloid protein buildup is almost certainly at least partly responsible for some of these symptoms in Alzheimer’s, therefore the fact that we have shown that SARS-CoV-2 has protein fragments that are capable of making similar amyloids means that it is vitally important that the medical [and] scientific community perform further research to determine if these amyloid deposits could be causing the brain fog symptoms in Covid-19 and long Covid.

    “As the connections between neurodegenerative disease, Covid-19 and neuroinflammation are becoming more apparent, interest in the field is growing. Around the same time as our paper in Nature Communications was published, [a similar paper was published] showing that products of the spike protein are capable of forming amyloids, and they also hypothesized that these may be related to long Covid.”

Reynolds states that outstanding questions remain. Researchers must first investigate whether amyloid deposits are observed in Covid-19 patients; if so, they would be able to begin “looking at the possibility of re-purposing ‘anti-amyloid’ therapies that have been developed to treat neurodegenerative diseases to combat the neurological symptoms of long [Covid].” As humans are repeatedly exposed to the virus in the coming months and years, it will also remain paramount to continue studying the virus and its behavior––including why the virus may produce amyloids during its viral replication cycle, since it “gains no benefit from killing brain cells.” Reynolds says: “The better we understand how the virus works on a molecular level, the better we can design antiviral therapies or vaccines.”

Earlier this year, a very small study out of Columbia University found that people who died of Covid-19 display “some of the same molecular changes found in the brains of people with Alzheimer’s disease.” At the time, the study’s lead researcher said that “one interpretation of these findings is that long [Covid] could be an atypical form of Alzheimer’s and/or that patients who had severe [Covid] could be predisposed to developing Alzheimer’s later in life… but much more research needs to be done before we can make more definitive conclusions.”

Data from Denmark have also shown that Covid outpatients are at increased risk of certain neurodegenerative disorders.