"But at the same time, we have also the technology to stop it, and the knowledge to stop it," he said, stressing the importance of "national unity, global solidarity".
During the briefing, Tedros also responded to a question about corruption linked to personal protective equipment (PPE), which he described as "criminal".
"Any type of corruption is unacceptable," he said.
"However, corruption related to PPE... for me it's actually murder. Because if health workers work without PPE, we're risking their lives. And that also risks the lives of the people they serve," the BBC quoted the Director-General as saying.
Tedros also said that the pandemic has given new impetus to the need to accelerate efforts to respond to climate change, Xinhua news agency.
"Throughout history, outbreaks and pandemics have changed economies and societies, this one will be no different."
Noting that the global health criris "has given us a glimpse of our world as it could be: cleaner skies and rivers... Building back better means building back greener".
In May, WHO published its Manifesto for a Healthy Recovery from Covid-19, with six policy prescriptions for a healthy and green recovery -- protecting nature, investing in water and sanitation, promoting healthy food systems, transitioning to renewable energy, building liveable cities, and stopping subsidies on fossil fuels.
Since then, over 40 million health professionals from 90 countries have sent a letter to G20 leaders, calling for a healthy recovery from the pandemic.
The WHO chief reiterated that "Covid-19 is a once-in-a-century health crisis. But it also gives us a once-in-a-century opportunity to shape the world our children will inherit - the world we want".
As of Saturday, the overall number of global coronavirus cases stood at 22,864,873, while the fatalities rose to 797,787.
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