By Pam Belluck June 15, 2021Updated 9:05 a.m. ET Karla Jefferies, 64, tested positive for Covid-19 in March 2020 and has been bothered by puzzling symptoms ever since. First, it was fatigue, fever, and no taste or smell. Then came brain fog, insomnia, a nagging smell of something burning, and an intermittent ringing in her...
