A WHO spokeswoman said that the organisation has seen "upticks" in COVID-19 cases as lockdowns ease in some countries.
"On upticks, yes we have seen in countries around the world - I'm not talking specifically about Europe - when the lockdowns ease, when the social distancing measures ease, people sometimes interpret this as 'OK, it's over'," WHO spokeswoman Margaret Harris told a UN briefing in Geneva.
"It's not over until there is no virus anywhere in the world," she added.
The second wave of coronavirus could be worsened by seasonal flu in the fall, as immunisation has been interrupted in many countries, the World Health Organisation said earlier.
The number of confirmed coronavirus cases worldwide has risen by nearly 130,000 in the past 24 hours to 6.4 million, and the death toll has topped 380,000, the World Health Organization (WHO) said on Thursday.
Americas continue to lead in the number of overall coronavirus cases, with 3 million infections. The region accounts for 168,553 related deaths.