Young people "are not invincible", the World Health Organization (WHO) stressed on Thursday, warning of growing evidence that patients with mild COVID-19 can have long-term health issues.
"Evidence suggests that spikes in cases in some countries are being driven in part by younger people letting down their guard during the northern hemisphere summer," WHO chief Tedros Adhanom Ghebreyesus said.
"We have said it before and we'll say it again: young people are not invincible. Young people can be infected; young people can die; and young people can transmit the virus to others," he added.
It comes after Dr Hans Kluge, WHO's regional director for Europe, told Euronews more and more young Europeans were testing positive for COVID-19.
"We see from reports both nationally and sub-nationally that now the spike in cases in quite a number of countries is primarily in age cohorts between 20 and 39," he said.
In several countries, including France and Germany, health experts have said that more young people are testing positive for the virus. Officials said that young people have been social distancing less often and have more contacts.
'I have no fear'
Indeed many young Europeans contacted by Euronews have said that although some aspects of life are different, they are still seeing as many friends as they did before coronavirus.
"I think I see as many people as before, but maybe less often because of the decrease in the number of events. I prefer outdoor meetings to limit wearing a mask," said Simon, a 33-year-old living in Lyon, France.
But he said his friends have stopped the French custom of greeting by kissing each other on the cheek.
Sarah, a 32-year-old who works for a non-profit foundation in Paris, said that she sees just as many people as before, and has since at least June when bars and restaurants reopened in France.
She said most people she knows aren't concerned about the outbreak.
"I have no fear in terms of the virus because I'm in a young population, and not at risk. I don't really frequent people who are at risk," Sarah added.
"There comes a point where the desire to resume normal life is stronger than the fear of dying," she added, explaining that people also wanted to start living again due to the economic crisis.
"I think I'm seeing as many people as before little by little," said Vincent, a 34-year-old in Lyon. "I'm using preventive measures, wearing a mask when necessary, washing my hands and maintaining distancing when possible."
Simon and Vincent agreed that they're more worried about "transmitting" the virus to others rather than getting it themselves.
Sarah said that around people at risk, however, she pays close attention to distancing and using preventive measures. Otherwise, it's just during "the rare times" that a friend is worried about the virus.
'Why take the risk?'
But WHO stressed on Thursday that even a mild COVID-19 infection can result in long term health implications.
Dr Maria van Kerkhove, WHO's COVID-19 technical lead, listed extreme fatigue, shortness of breath, and difficulty resuming normal activity as some of the longer-term effects people who had a mild infection can experience.
WHO's executive director of health emergencies programme, Michael Ryan, also cited evidence of prolonged inflammatory changes to patients' cardiovascular system.
He added that little is still known about the longer-term implications of the virus.
"Why take the chance? Why take the risk?" he asked. "Don't take a risk that you cannot quantify."
Both urged young people to wear masks, wash their hands regularly and avoid crowded places with van Kerkhove flagging that "we're consistently seeing nightclubs as being amplifiers of transmissions".
For Dr Kluge, the increase in the number of cases is largely "due to changed behaviour in human beings".
He said health experts needed to change their messaging to young people.
"The key issue here is to tailor our risk communication to that group or segment of the population and getting away from younger people are less vulnerable," Dr Kluge said.
"Blaming is the worst thing we can do," Dr Kluge added, explaining that they need to convince young adults with positive messages.