The WHO has denied President Donald Trump 's claims that coronavirus was created in a Chinese labratory.
The US President told a White House media event that the disease was man-made and he had seen evidence.
When asked if he had seen anything to suggest Covid-19 was created in a laboratory, Trump replied: "Yes, I have. Yes, I have.
"And I think the World Health Organization should be ashamed of themselves because they're like the public relations agency for China."
But, Maria Van Kerkhove, WHO technical lead on Covid-19 dismissed Trump's claims, stating coronavirus comes from bats, the Mirror reports.
Speaking on the BBC's Andrew Marr programme, she said: "Coronaviruses normally circulate in animals and many coronaviruses are circulating in bats.
"Most emerging pathogens, viruses, come from an animal reservoir. Everything that we have seen about the novel coronavirus, Covid-19 or Sars-CoV-2, of the tens of thousands of sequences that are available, full genome sequences and partial sequences, compared to other coronavirus sequences that are available, this is of a natural origin.
"And it originally comes from bats because the coronaviruses come from bats. What we need to do is really understand what we call the intermediate host - what is the animal that was infected from bats that potentially infected humans?
"It's important that we know this because from a public health point of view, it's very important that we find the animal host so that we prevent this, (what) we call spillover from transmission from an animal to a human, we prevent that spillover from happening again."
Dr Van Kerkhove added that all countries must remain "on alert" over the possibility of further transmission of coronavirus.
When asked if a second wave of infection could be likely in countries that have started to ease their lockdowns, Ms Van Kerkhove said: "It's certainly possible. What we're seeing in a number of countries that have been successful in suppressing transmission is that many more people remain susceptible."
She added: "All countries must remain on alert for the possibility of additional transmission even if they have been successful in suppressing transmission in the first round."
Following comments by Prime Minister Boris Johnson that face masks will be "useful" as part of measures to come out of lockdown, Dr Van Kerkhove said that masks are recommended for those who are feeling unwell.
She said: "We do recommend the use of masks for people who are feeling unwell, but masks alone will not solve the problem, they cannot solve the problem, and especially if you're thinking about lockdowns and you're thinking of lifting lockdowns.
"There has to be a number of measures that have to be put in place before lockdowns can be released and it must be done in a slow and staggered approach."
Asked about the longer-term health impact of the virus, Dr Van Kerkhove said: "The majority of people who are infected with Covid-19 will make a full recovery.
"But there will be some people that may have some longer term effects. It affects the lungs, it affects the body in different ways and so we may see some damage to the lungs.
"We need to follow individuals over time. We're in our fourth month of this pandemic so it's very, very early days."
