Bill Gates has warned that we might not have seen the worst of the Covid-19 pandemic and that a more deadly variant of the virus could emerge.

The Microsoft billionaire said he did not want to be “all doom and gloom” but there was a “5pc risk” that the pandemic could get worse and urged world leaders to spend more to increase preparedness for health threats.

Mr Gates has long warned of the global threats posed by viruses. He previously gave a talk in 2015 claiming the world was “not ready for the next epidemic” and that viruses, not war, pose the greatest risk of “global catastrophe”.

The philanthropist told the Financial Times: “We’re still at risk of this pandemic generating a variant that would be even more transmissive and even more fatal.

“It’s not likely, I don’t want to be a voice of doom and gloom, but it’s way above a 5pc risk that this pandemic, we haven’t even seen the worst of it.”

The philanthropist also called for a team of experts, costing around $1bn, that would be managed by the World Health Organisation (WHO) to spot and prevent future pandemics.

He said: “The amount of money involved is very small compared to the benefit and it will be a test: can global institutions take on new responsibilities in an excellent way, even in a time period where US-China [relations are] tough, US-Russia is extremely tough?”

It comes as the WHO’s director general Dr Tedros Adhanom Ghebreyesus urged countries to maintain surveillance of coronavirus infections, saying the world was “blind” to how the virus is spreading because of falling testing rates.

“As many countries reduce testing, WHO is receiving less and less information about transmission and sequencing,” he told a news conference at the UN agency’s headquarters in Geneva.

“This makes us increasingly blind to patterns of transmission and evolution.”

Bill Rodriguez, chief executive of FIND, a global aid group working with WHO on expanding access to testing, said “testing rates have plummeted by 70 to 90pc”.

“We have an unprecedented ability to know what is happening. And yet today, because testing has been the first casualty of a global decision to let down our guard, we are becoming blind to what is happening with this virus,” he added.

In other developments, an analysis of data from 50 studies has shown that almost half of the people recovering from coronavirus are still experiencing post-Covid conditions.