Allison Guy was having a great start to 2021. Her health was the best it had ever been. She loved her job and the people she worked with as a communications manager for a conservation nonprofit. She could get up early in the mornings to work on creative projects. Things were looking “really, really good,” she says—until she got Covid-19.
While the initial infection was not fun, what followed was worse. Four weeks later, when Guy had recovered enough to go back to work full-time, she woke up one day with an overwhelming fatigue that just never went away. It was accompanied by a loss of mental sharpness, part of a suite of sometimes hard-to-pin-down symptoms that are often referred to as Covid-19 “brain fog,” a general term for sluggish or fuzzy thinking. “I spent most of 2021 making decisions like: Is this the day where I get a shower, or I go up and microwave myself a frozen dinner?” Guy recalls. The high-level writing required for her job was out of the question. Living with those symptoms was, in her words, “hell on earth.”
Many of these hard-to-define Covid-19 symptoms can persist over time—weeks, months, years. Now, new research in the journal Cell is shedding some light on the biological mechanisms of how Covid-19 affects the brain. Led by researchers Michelle Monje and Akiko Iwasaki, of Stanford and Yale Universities respectively, scientists determined that in mice with mild Covid-19 infections, the virus disrupted the normal activity of several brain cell populations and left behind signs of inflammation. They believe that these findings may help explain some of the cognitive disruption experienced by Covid-19 survivors and provide potential pathways for therapies.
For the past 20 years, Monje, a neuro-oncologist, had been trying to understand the neurobiology behind chemotherapy-induced cognitive symptoms—similarly known as “chemo fog.” When Covid-19 emerged as a major immune-activating virus, she worried about the potential for similar disruption.
Very quickly, as reports of cognitive impairment started to come out, it was clear that it was a very similar syndrome. The same symptoms of impaired attention, memory, speed of information processing, dis-executive function—it really clinically looks just like the ‘chemo fog’ that people experienced and that we’d been studying.
In September 2020, Monje reached out to Iwasaki, to an immunologist. Her group had already established a mouse model of Covid-19, thanks to their Biosafety Level 3 clearance to work with the virus.
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