The coronavirus’ spike protein, often depicted as the red arms of the virus, can cross the blood-brain barrier in mice, researchers have found. More and more evidence is coming out that people with COVID-19 are suffering from cognitive effects, such as brain fog and fatigue. The new finding strongly suggests that SARS-CoV-2, the cause of COVID-19, can enter the brain. The spike protein, often called the S1 protein, dictates which cells the virus can enter. Usually, the virus does the same thing as its binding protein, says lead author William A. Banks, a professor of medicine at the University of Washington School of Medicine and a Puget Sound Veterans Affairs Healthcare System physician and researcher. Banks says binding proteins like S1 usually by themselves cause damage as they detach from the virus and cause inflammation.