GENEVA: The World Health Organization on Thursday warned that spikes in coronavirus transmission in a number of countries were being driven by young people "letting down their guard".

"Young people are not invincible," WHO chief Tedros Adhanom Ghebreyesus told a virtual news conference in Geneva.

While the pandemic, which has killed nearly 670,000 and infected more than 17 million people worldwide, has disproportionately impacted the elderly and people with pre-existing conditions, he stressed that "younger people are at risk too".

He lamented that a major challenge in trying to rein in the novel coronavirus was "convincing younger people of this risk".

He said there was evidence that "spikes of cases in some countries are being driven in part by younger people letting down their guard during the northern hemisphere summer."

WHO's technical lead for Covid-19 Maria Van Kerkhove lamented in particular that nightclubs in a number of places had become "amplifiers" of transmission.