Six months since the coronavirus outbreak began, the pandemic is far from over, the World Health Organization has said, warning that "the worst is yet to come".

Reaching the half-year milestone just as the death toll surpassed 500,000 and the number of confirmed infections topped 10 million, the WHO said it was a moment to recommit to the fight to save lives.

"Six months ago, none of us could have imagined how our world - and our lives - would be thrown into turmoil by this new virus," WHO Director-General Tedros Adhanom Ghebreyesus told a virtual briefing.

"We all want this to be over. We all want to get on with our lives. But the hard reality is this is not even close to being over.

"Although many countries have made some progress, globally the pandemic is actually speeding up.

"We're all in this together, and we're all in this for the long haul.

"We will need even greater stores of resilience, patience, humility and generosity in the months ahead.

"We have already lost so much - but we cannot lose hope."

Dr Tedros also said that the pandemic had brought out the best and worst humanity, citing acts of kindness and solidarity, but also misinformation and the politicisation of the virus.

In an atmosphere of global political division and fractures on a national level, "the worst is yet to come. I'm sorry to say that," he said.

"With this kind of environment and condition, we fear the worst."

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Meanwhile, the WHO sees tremendous work towards finding a safe and effective vaccine to prevent Covid-19, but there are no guarantees of success, the head of its emergencies programme, Mike Ryan, said.

The WHO is sending a team to China next week to help research the origin of the virus.

Brazil still faces a "big challenge" in fighting the disease, the organisation warned, urging federal and state authorities there to work together more closely.

"There is no question. Brazil is still facing a big challenge," Mr Ryan said. He described the situation in the Americas generally as "difficult".

Asked by a journalist to react to US President Donald Trump's use of the term "kung flu" or other references to the virus as being Chinese, Mr Ryan urged the use of an "international discourse that is based on mutual respect."

He added that "many people around the world have used unfortunate language in this response. We try to focus on the way ahead, try to focus on what we need to do."