B.S.N.

As hospitals increasingly require nurses to have a four-year degree, one of the most popular online degrees is the “R.N. to B.S.N.,” for people who are already registered nurses to earn a bachelor of nursing degree.

That shift has contributed to a surge in enrollment in nursing courses at four-year colleges, particularly at the more than 600 schools that have opened “R.N. to B.S.N.” programs, for people who are already registered nurses to earn bachelor’s degrees.

Its online R.N. to B.S.N. program began in the late 1990s with a few dozen students and today has 650.

But even the B.S.N. may eventually not be enough.