Four viruses are currently circulating in the United States, which some have referred to as a "quad-demic." Data from the Centers for Disease Control and Prevention showed an increase in three respiratory viruses—COVID-19, flu and RSV—and the gastrointestinal disease norovirus. Emergency department visits are "high" and "very high" for flu and RSV, respectively, and "elevated" for COVID-19 across the U.S., according to the CDC. As of the week ending Jan. 4, 18.6% of tests for influenza are returning positive, as are 11.6% of RSV tests and 6.9% of COVID tests. Meanwhile, for norovirus, 27.91% of weekly tests have come back...