Weekly COVID-19 incidence among younger adults was up 55% in August, and more than doubled in the Northeast and Midwest, researchers found.
From Aug. 2 to Sept. 5, the proportion of cases occurring among adults ages 18 to 22 approximately doubled from 10.5% to 22.5%, reported Phillip Salvatore, PhD, and colleagues from the CDC.
By U.S. Census region, weekly incidence of COVID-19 rose 144% in the Northeast and 123.4% in the Midwest, with an increase of 43.8% in the South, the authors wrote in an early edition of the Morbidity and Mortality Weekly Report.
Researchers added that about 45% of this age group are enrolled in colleges and universities, noting, “as these institutions reopen, opportunities for infection increase” and stressed the importance of mitigation efforts and monitoring reports of COVID-19 cases in young adults.
They examined jurisdictional health department data from probable and confirmed COVID-19 cases from May 31-Sept. 5 in 50 states, the District of Colombia, Guam, Puerto Rico, the U.S. Virgin Islands, and the Northern Mariana Islands.
Weekly SARS-CoV-2 real-time reverse transcription-polymerase chain reaction (RT-PCR) testing volumes were from COVID-19 electronic laboratory reporting data submitted by state health departments in 37 states and directly by public, commercial, and reference labs in 13 states and D.C., with data on positive cases aggregated by calendar week.
National weekly incidence of COVID-19 cases among the 18-22 age group increased from 110 to 180 cases per 100,000 from Aug. 2 to Aug. 29, a 62.7% rise, before dipping to 171 per 100,000 from Aug. 30-Sept. 5.
While weekly case incidence among this age group in the Northeast rose from 53 to 130 per 100,000, the authors noted incidence in all other age groups have remained below 53 per 100,000 since July 4. Weekly incidence was smallest in the West, declining 1.7% during August, the authors noted.
Testing incidence among adults ages 18 to 22 rose 49.3%, with a 170.6% increase in the Northeast and a 65.2% jump in the Midwest. Testing in the South increased 7.0%, and declined 6.2% in the West.
Examining demographic data, the proportion of weekly cases among white adults ages 18 to 22 increased from 33.8% to 50.8% from May 31-June 20, and the proportion of cases from Aug. 2-Sept. 5 grew from 52.1% to 77.3%. However, the authors noted incidence in other racial/ethnic groups remained stable or declined.
A second report in the MMWR by Catherine Donovan, PhD, of the North Carolina Division of Public Health, discussed how multiple COVID-19 clusters were detected at a university in North Carolina, with 670 laboratory-confirmed cases of COVID-19, 96% of them among patients age 22 or younger.
Residence halls were at 65-80% capacity, with most students in double rooms. Undergraduate enrollment was 19,690 students, and 5,800 students resided on campus as of Aug. 10, when in-person classes began.
The university opened on Aug. 3, and over the next 3 weeks, 18 clusters of five or more epidemiologically linked cases within 14 days of each other were reported, and 30% of cases were linked to a cluster, the authors said.
Among the 18 case clusters, eight were in residence halls, five were among students belonging to a fraternity or sorority, four were among athletic teams, and one was in off-campus housing. Clusters ranged from 5 to 106 patients, with the largest one linked to a university-associated apartment complex, the authors said.
Median patient age was 19, and 47% of cases were in boys, though gender information was missing for some of the patients. Among cases in undergraduate students, 36% resided on campus, at least 8% were members of a fraternity or sorority, and 8% were student athletes.
On Aug. 19, all classes transitioned to online, and students living on campus in residence halls were required to return home and instructed to quarantine for 14 days.
As of Aug. 25, no COVID-19 patients from the campus were hospitalized, had reported cases of multi-system inflammatory syndrome in children (MIS-C), or died, though one student was kept for extended observation in the hospital emergency department.
The authors said this suggests in addition to enforcement of mask requirements, more stringent mitigation measures and comprehensive mitigation strategies are required at colleges and universities, which would include “efforts to reduce the density of on-campus housing, increase testing for SARS-CoV-2, and discourage student gatherings.”
Salvatore and colleagues disclosed no conflicts of interest.
Wilson and colleagues disclosed no conflicts of interest.