Is 18 minutes of fast jogging 5 days a week enough to maintain cardiovascular wellness, weight and fitness?

Jogging: Depending on your goals this can be sufficient for maintenance of cv wellness, weight and fitness. I am assuming that you are running a 6-8 mile an hour pace as you describe a fast jog. If you are limited to 18 minutes you may want to vary intensity at time and "run" followed by fast jog. Interval training has been found to increase cv fitness, lower body fat, and improve fitness above "jogging.

Jogging: 18min is generally the minimum time for aerobic progress. If you want to be sure you're getting aerobic benefit; you might move out to 30min. Sessions either at the same level or decreased enough to let you get to 30min. The suggestion to mix in interval training is certainly a good one.