A virus even more transmissible and fatal than Covid-19 will lead the world into the next pandemic, the director-general of the World Health Organization (WHO) has said, noting the “evolutionary certainty” of such an occurrence.

“Make no mistake, this will not be the last time the world faces the threat of pandemic,” Tedros Adhanom Ghebreyesus told the UN agency’s annual assembly of health ministers from its 194 member states on Monday. “It’s an evolutionary certainty that there will be another virus with the potential to be more transmittable and more deadly than this one.”

On a more positive note, Ghebreyesus said the global number of Covid-19 cases and deaths reported has been decreasing for three consecutive weeks.

But the WHO chief stressed that the world remains “in a fragile situation” and cautioned against any nation assuming it is “out of the woods, no matter its [Covid] vaccination rate.”

He also reiterated his previous calls for governments to donate Covid-19 inoculation doses to the COVAX vaccine-sharing facility backed by the WHO and the Gavi vaccine alliance.

So far, the global rollout of Covid jabs has seen more than 75% of all doses administered in just 10 countries, according to WHO data. Ghebreyesus said such “scandalous inequity” is “perpetuating” the pandemic. He has previously referred to the situation as “vaccine apartheid.”

The efficacy of the world’s current crop of Covid-19 vaccines does not appear to be undermined by emerging variants of the virus, such as the strain first detected in India, Ghebreyesus said. But he did warn variants are “changing constantly” and that any future strains could “render our tools ineffective and drag us back to square one.”