Virus World

Highlights

Summary

The growing number of people with post-Covid syndrome is prompting researchers to look to chronic fatigue syndrome (ME/CFS) for clues. Some survivors of acute bouts of Covid-19 experience a range of persistent medical issues — some lasting for weeks, or even months — that include profound exhaustion, trouble thinking or remembering, muscle pain, headaches, and more. One survivor described it as feeling like she was “hit by a truck.”  Anthony Fauci, the country’s top infectious diseases expert, acknowledged this month that the symptoms in many of these unrecovered patients are “highly suggestive” of myalgic encephalomyelitis, the disabling illness also commonly called chronic fatigue syndrome or ME/CFS. “This is something we really need to seriously look at,” said Fauci. 

Fauci’s observation, echoed by others, is vitally important, and not only because it provides a warning about the pandemic’s potentially devastating long-term health effects. By noting the possible connection between “post-Covid syndrome” and ME/CFS, Fauci has highlighted the long-neglected field of post-viral illness — a poorly understood phenomenon that likely holds important clues about the causes of, and treatments for, both conditions.

In recent decades, researchers have documented persistent sequela among some people who had acute infections of diseases like SARS, West Nile virus, and the 2009 H1NI influenza virus. Why some people are vulnerable to these chronic symptoms isn’t known. The name “myalgic encephalomyelitis” was coined in the 1950s after an outbreak in a London hospital of what appeared to be a viral illness with prolonged complications. No pathogen was identified as the cause. After an outbreak with similar features occurred in Lake Tahoe in the mid-1980s, a team led by the Centers for Disease Control and Prevention called it chronic fatigue syndrome — and the name became widely adopted. The CDC estimates that up to 2.5 million Americans have ME/CFS, although many remain undiagnosed. A significant minority are homebound, even bedbound. As with post-Covid syndrome, most people report that their illness began with an acute episode of infectious disease, often mononucleosis or the flu. Although studies have documented a range of neurologic, immunologic, metabolic, and other dysfunctions, no specific causes have been identified for ME/CFS and no pharmacological treatments have been developed for it. The cardinal symptom is not fatigue per se, but a prolonged relapse of exhaustion, cognitive dysfunction, and other symptoms after a minimal amount of activity. This is generally called “post-exertional malaise.” For decades, many people with ME/CFS have been dismissed by their doctors, employers, and even family members as experiencing exaggerated or psychosomatic ailments. Some people with post-Covid syndrome are also reporting they are being told that their troubling symptoms likely result from anxiety, depression, or post-traumatic stress....

Researchers found associations between certain viral illnesses and the risk of Alzheimer’s and other neurodegenerative diseases.  Neurodegenerative diseases can damage different parts of the nervous system, including the brain. This may lead to problems with thinking, memory, and/or movement. Examples include Alzheimer’s disease (AD), multiple sclerosis (MS), and Parkinson’s disease (PD). These diseases tend to happen late in life. There are few effective treatments. Previous findings have suggested that viruses may play a role in certain neurodegenerative diseases. For example, a recent study found a link between Epstein-Barr virus infection and the risk of MS. There are also concerns about cognitive impacts from SARS-CoV-2, the virus that causes COVID-19. A research team led by Drs. Mike Nalls, Kristin Levine, and Hampton Leonard of NIH's Center for Alzheimer’s and Related Dementias examined links between viruses and neurodegenerative disease more generally. To do so, they analyzed data from the FinnGen project. This is a repository of biomedical data, or biobank, from more than 300,000 people in Finland. The team searched the biobank for people who had been diagnosed with one of six different conditions: AD, amyotrophic lateral sclerosis (ALS), generalized dementia, vascular dementia, PD, and MS. They then checked how many had been hospitalized for a viral illness before. To confirm their findings, they looked for the same associations in the UK Biobank, which contains data from almost 500,000 people in the United Kingdom. Results appeared in Neuron on January 19, 2023.

The researchers found 45 associations between viruses and neurodegenerative diseases in FinnGen. Of these, 22 also appeared in the UK Biobank. The strongest association was between viral encephalitis—brain inflammation caused by a virus—and AD. A person with viral encephalitis in the FinnGen database was 30 times as likely to be diagnosed with AD as someone without encephalitis. Results were similar in the UK Biobank; people with viral encephalitis were 22 times as likely to develop AD as those without. The team also found, in FinnGen, the association between Epstein-Barr virus and MS that was described before. The association wasn’t seen in the UK Biobank, but this may reflect how the different biobanks use hospital diagnostic codes; Epstein-Barr viruses are common and so often not noted. Influenza with pneumonia was associated with all the neurodegenerative diseases except MS. The researchers only included cases of influenza severe enough to need hospitalization in the study. Thus, these associations only apply to the most severe cases of influenza. FinnGen contains data on the same people over time. The team used this to examine how the associations depended on the time since infection. They found that some viral infections were associated with increased risk of neurodegenerative disease as much as 15 years later. The researchers note that vaccines exist for some of the viruses they identified. These include influenza, varicella-zoster (which causes chickenpox and shingles), and certain pneumonia-causing viruses. Vaccination might thus reduce some of the risk of the conditions they examined. “The results of this study provide researchers with several new critical pieces of the neurodegenerative disorder puzzle,” Nalls says. “In the future, we plan to use the latest data science tools to not only find more pieces but also help researchers understand how those pieces, including genes and other risk factors, fit together.”