One of the many familiar stories to emerge in the last year is the simple one of an athlete testing positive for COVID-19, holing up for a week or two, then returning like any other minor injury. To the athlete and their team, it's not nearly that simple, but that's how it looks to many fans.
But sometimes it plays out differently, and for the worse due to the potential extent of COVID-19 symptoms and risk factors.
That is the case of former Clemson defensive end Justin Foster, who announced his retirement from football on Wednesday due to the lingering effects of COVID-19 on his asthma and allergies. Foster opted out of the 2020 season after contracting the virus, and said he still encounters "severe difficulty" when engaging in physical activities.
Foster further detailed the effects of COVID-19 on his body in an interview with The Athletic's Grace Raynor, including that doctors found that he was "allergic to pretty much everything in the environment right now." Before COVID-19, he said he was only allergic to things like bees.
The worst lingering effects are reportedly his respiratory struggles, to the point that walking can leave him out of breath:
My biggest thing is a little jog or a little run, I’m still having breathing problems. Even just getting to the point where I can work out daily is still a challenge. I’m doing well, but at the end of the day, I’m just worried about my health and getting that straight before I start on anything else.
[When I say I have "bad" days], it was more just breathing. It was more of, it was either an asthma attack, or I was just so short of breath that just a normal jog or walk would take my breath away. The everyday basis.
Clemson's Justin Foster isn't alone
Foster isn't the only athlete to feel the effects of COVID-19 long after the virus left his body, or even the only Clemson defensive end. Teammate Xavier Thomas also had symptoms linger for months, forcing him to miss all of preseason and miss the first month of the season.
Several athletes across sports have been similarly struck. Boston Celtics star Jayson Tatum says it still messes with his breathing. Atlanta Braves MVP Freddie Freeman prayed for his life when his fever hit 104.5 degrees. UFC breakout star Khamzat Chimaev lost the biggest fight of his life and could be out for months. Boston Red Sox left-hander Eduardo Rodriguez missed the whole season with a COVID-related heart issue. Jacksonville Jaguars running back Ryquell Armstead did the same.
Many more athletes have returned from COVID-19 with little visible difficulties, but that's just how the virus works. Some are lucky enough to be asymptomatic. Others can barely jog long distances. Expose enough athletes to the virus, and stories like Foster's are inevitable.
Professional athletes face little mortal risk when they contract COVID-19 thanks to their age and physical condition, but the virus can definitely impact them on the field. In Foster's case, it hit hard enough to take him off the field for good.
More from Yahoo Sports: