The argument has been made many times that restrictions should be relaxed on younger age groups who are not as much at risk for acute cases of the virus. But Spain's recent outbreak is showing why that is just wishful thinking and is a warning to the US as we open college campuses. Spain had the virus well under control in June. The central government ended its emergency measures on June 21. The regional governments were left to manage the virus and let things return to normal very quickly. Young people started going to clubs again and having large parties in public parks. The new outbreak started among ages 15-29, but spread to all age groups within about seven weeks (see the chart in the article about 2/3rds down).
Currently in the US, outbreaks are starting on many college campuses with clusters linked to fraternity and sorority parties as well as off campus clubs and parties. These outbreaks will spread to college towns and then fan out across the country as students come home either to try to isolate after getting infected or for weekend and holiday visits. This may also coincide with some states relaxing social distancing after seeing rates drop after the summer surge, high school and middle school returning for face to face instruction and with the potential for increased transmission due to winter indoor heating and colder drier air outside.
The seeds of a fall/winter outbreak have been planted. A lot of people in the US are now very vigilant about exposure, wearing masks and limiting activities. This may save us from a huge explosion of cases this fall. But with many states heading towards relaxing restrictions, it is hard to imagine getting through the fall and winter without another big surge in cases pushing our health care system to the bring again.
https://www.ft.com/content/6a5e61f5-7a35-4ad9-b57d-98f1dfa107ad