I wouldn't worry just yet. There may be a slowdown in tourism and travel, but unless the government orders a shutdown, and contrary to public statements. the Broadway League will put profits ahead of this outbreak (despite a severe snow storm, the shuttering of public transit, and Disney closing its shows, a little over a year ago the mayor's office had to call the Broadway League and tell them directly to cancel performances).
And while it does sound a bit morbid, the most at-risk are older adults and people with serious chronic medical conditions (such as heart disease, heart disease, diabetes) and weaker immune systems. They aren't mutually exclusive, and the average age is 42yo (meaning a significant umber of theatergoers are much older). That said, school closures are not really considered extreme measures, so I wouldn't too much into it is schools are closing.
And while people certainly shouldn't panic, NYC is not an isolated bubble. According to NBC, the number of novel coronavirus cases in the tri-state area surged by 216 percent between late Friday and Monday afternoon, from 49 cases to 155. 16 of those are in NYC. And just because there "only" 49 cases in the area, doesn't mean this isn't spreading rapidly. Over 114,000 people have been infected worldwide, from a virus that was seen only in one region in China. In 2-month's time. That's not insignificant. 3.5% of those infected have died. Again, this is within a 2-month period (approximately). Comparing it to other illnesses is absurd, at this point. As of now, it is more deadly than the flu.