TABLE 2. Model-based estimates of prevalence and number of persons aged ≥18 years with any select underlying medical condition, by urban/rural county classification — United States, 2018.

County classification*	No. of counties	Median county prevalence % (range)	Median county no. of persons (range)
Metropolitan
Large central metro†	68	39.4 (23.9–48.1)	301,744 (43,770–2,877,316)
Large fringe metro§	368	43.9 (26.4–56.9)	34,221 (1,611–725,284)
Medium metro¶	372	45.5 (22.0–61.7)	33,687 (659–332,209)
Small metro**	358	45.8 (27.8–62.2)	26,683 (41–87,153)
Nonmetropolitan
Micropolitan††	641	47.8 (24.3–64.6)	13,979 (176–59,820)
Noncore§§	1,335	48.8 (26.8–66.2)	4,300 (47–29,469)

* Based on 2013 Urban-Rural Classification Scheme for Counties from the National Center for Health Statistics, CDC.

^† Large central metro counties in metropolitan statistical areas (MSAs) of 1 million population that 1) contain the entire population of the largest principal city of the MSA, or 2) are completely contained within the largest principal city of the MSA, or 3) contain ≥250,000 residents of any principal city in the MSA.

^§ Large fringe metro counties in MSA of ≥1 million population that do not qualify as large central.

^¶ Medium metro counties in MSA of 250,000–999,999 population.

** Small metro counties are counties in MSAs of <250,000 population.

^†† Micropolitan counties in MSAs.

^§§ Noncore counties not in MSAs.