A survey conducted by the Centres for Disease Control and Prevention (CDC) found that even mild symptoms may lead to long-term complications.
Nearly 50% of the 300 people surveyed who tested positive and had a cough still exhibited symptoms 14 to 21 days later.
The study also found that people aged 18-34 with no pre-existing conditions still had symptoms three weeks after being diagnosed.
A separate study found that those with Covid-19 had structural changes to their heart two months after recovering.
The CDC has recommended that young people continue practicing social distancing, mask-wearing and other health measures.