Johns Hopkins doctors and nurses fanned out through an Ellicott City nursing home. They tested residents for COVID-19, assessed the health of those who had the disease, talked with staff members about infection-prevention strategies and provided moral support. The facility wasn’t the first in Maryland to contend with COVID-19. But it was one of the first to get help from the Johns Hopkins Go Team — a disaster response unit formed a decade ago to provide clinical and logistical support to communities around the world that are reeling from hurricanes, earthquakes and other catastrophes.