The is an animal study focusing on the lingering effects of SARS-CoV-2 infection in the brains of hamsters. 40 animals were used in total. They assessed the differences between infected animals and negative controls during the symptomatic phase (3 days) and post-infection (14 days). They found an increased number of microglia cells in the olfactory bulb after 14 days and found an increased level of both phosphorylated tau and alpha-synuclein in cortical neurons post-infection. The authors note that the levels of hyperphosphorylated tau enabled them to reliably differentiate between animals that had and had not been infected. Phosphorylated tau and alpha-synuclein are hallmarks of neurodegenerative disease. This raises concerns that COVID-19 can induce a tauopathy or synucleinopathy that persists after acute infection and may provide insight into the pathophysiology of long COVID.

There was a companion piece published that provides a more in-depth summary of the original article: https://www.thelancet.com/journals/ebiom/article/PIIS2352-3964(22)00252-3/fulltext