The UN's health agency reports concerns about more severe variants of SARS-CoV-2 evolving globally.

The latest figures from the WHO show that between 24 June and 21 July 2024, new hospitalizations increased by 11% and ICU admissions by 3% compared to the previous month.

“Data from our sentinel-based surveillance system across 84 countries reports that the percent of positive tests for SARS-CoV-2 has been rising over several weeks,” said the WHO's Dr. Maria Van Kerkhove.

Deaths due to COVID were also up 26% in recent weeks. However, the WHO urges caution when interpreting reported data, as testing and sequencing for COVID has decreased, and many countries report results with a delay.

Overall test positivity for SARS-CoV-2 is above 10%. However, Dr. Van Kerkhove warned that in Europe, that percentage is above 20%.

Are we seeing a global surge in COVID cases?

Ziyad Al-Aly, a COVID physician-scientist at Washington University in St. Louis, US, said we should take the rise in hospitalizations seriously, as it's "always wise to prepare for the worst and hope for the best."

"The uptick in the US was preceded by a COVID wave in Singapore. Unfortunately, a lot of countries are not tracking and reporting these metrics. So we are flying blind," Al-Aly told DW via email.

The good news is that COVID hospitalizations are still well below levels from last winter. The severity of infections also seems to be lower than it was earlier in the pandemic, according to Paul Hunter, a professor of medicine at University of East Anglia in the UK.

However, Hunter stressed that these patterns of COVID surges are now part of normal life given that "SARS-CoV-2 will likely be with us for generations. Rising and falling numbers will be part of our future for our lifetimes at least," he said.

FLiRT COVID variants driving new cases

The recent minor uptick in COVID cases appears to be due to several new subvariants called FLiRTs.

They are descendants of the now-dominant JN.1 variant, which is itself a descendant of omicron but with certain additional mutations. Members of the FLiRT group include KP.2, KP.3 and JN.1.7.1.

"The FLiRT variants are named after their specific mutations — Furin-like cleavage site, L452R, and T478K. Silly I know, but the name has stuck," said Hunter.

While data is limited, Hunter said "there is no evidence so far that these variants are any more harmful than previous variants and may even be less so."

Al-Aly was more cautious, saying it's too early to tell if the new FLiRT variants are more or less harmful than previous variants.

"We are still learning about the new variants KP.1, KP.2, KP.3, LB.1; there is some evidence that some of these are more transmissible and may be more immune evasive. This may explain the growth advantage and the uptick in hospitalizations in some regions. But more data is needed before we have more definitive answers," he said.

What's causing the summer COVID surge?

The evidence so far points to falling population immunity to COVID. 

"Sterilizing immunity following an infection or vaccination only lasts four to six months on average, so immunity gained from infections during winter or the autumn vaccination campaign will have already been lost for the most part," said Hunter.

Most people's immunity to COVID comes from a mix of infections and vaccine. This so-called hybrid immunity has given better protection against infection and severe disease than either alone.

Hunter suspects most current reports of COVID hospitalizations in the UK are older or vulnerable people, because the only testing and reporting done is from people seeking medical care.

Hunter emphasized that elder people, and those at higher risk of severe COVID infections, should take extra precautions to prevent infections.

"So if you are a 75 year old and had your autumn booster last year, avoided infection over winter and then did not to take up the spring booster you would now have very little sterilizing immunity left," he said.

"People ask me all the time: Can one still get long COVID with the new variants and the answer is very likely yes," said Al-Aly.

Edited by: Martin Kuebler

This article was first published on 5th July 2024. It has been updated on 15th August 2024 to reflect new data on COVID deaths, positive tests, hospital and ICU admissions.