The number of new coronavirus cases and deaths reported to the World Health Organization fell for the third week in a row, a trend that may have been helped by the cancellation of testing and surveillance programs.

The more than 7 million new cases reported were down 24 percent from a week earlier, the U.N. health agency said in its latest weekly report on the pandemic released late Tuesday. Global weekly COVID-19 deaths fell 18% to more than 22,000.

The WHO said the reduction “should be interpreted with caution” as many countries where the virus is starting to recede have changed their testing strategies, meaning far fewer cases have been detected.

New cases and deaths are falling in every region of the world, including the Western Pacific, where a surge in infections has prompted China to impose a draconian lockdown.

WHO said it was monitoring several mutants of the virus derived from omicron variants, including some recombinant forms of existing omicron subvariants.

In a separate statement, the health organization said scientists in Botswana and South Africa had detected new forms of omicron variants, labelled BA.4 and BA.5, but it was uncertain whether they were more contagious or dangerous.

To date, new versions of omicron have been detected in 4 individuals in Botswana and 23 individuals in South Africa. Outside Africa, scientists have confirmed cases in Belgium, Denmark, Germany and the UK.

The WHO said that so far, there is no evidence that the new sub-variant spreads any differently than the original omicron variant.

Dr. Matshidiso Moeti, WHO Africa director, said in a statement: “There is no reason to be concerned about the emergence of new subvariants. We have not observed a significant spike in cases, hospitalizations or deaths.”

The agency is calling on all countries to sequence at least 5% of COVID-19 samples; many countries, including the UK, Sweden and the US, have recently cancelled widespread testing programmes as the number of severe cases plummets.

Still, the U.S. will soon have 1 million COVID-19 deaths, and the virus continues to gain traction in China.

Officials have warned that despite Shanghai’s “zero tolerance” approach, with some residents confined to their homes for three weeks or more, its recent surge in cases involving omicron remains unchecked.

The lockdown has frustrated Shanghai residents as they run out of food and cannot be delivered. Censors worked hard to weed out complaints from social media.

State-controlled media described a successful campaign to provide food and other supplies, and exhorted residents to “persistence is victory”.