The study, tracking the health insurance records of nearly 2 million people in the United States who contracted the coronavirus last year, found that one month or more after their infection, almost one-quarter — 23 percent — of them sought medical treatment for new conditions. Those affected were all ages, including children. Their most common new health problems were pain, including in nerves and muscles; breathing difficulties; high cholesterol; malaise and fatigue; and high blood pressure. Other issues included intestinal symptoms; migraines; skin problems; heart abnormalities; sleep disorders; and mental health conditions like anxiety and depression. Post-Covid health problems were common even among people who had not gotten sick from the virus at all, the study found. While nearly half of patients who were hospitalized for Covid-19 experienced subsequent medical issues, so did 27 percent of people who had mild or moderate symptoms and 19 percent of people who said they were asymptomatic.