Need for vigilance amid new 'Nimbus' Covid variant

What you need to know

• NB.1.8.1. — also called "Nimbus” — is a subvariant of the dominant Omicron variant of SARS-CoV-2.
• It has been detected in South and Southeast Asia and circulating in many EU/EEA countries. It may lead to hospitalizations over the summer.
• The European centre for disease prevention and control (ECDC) recommends boosters for at-risk groups or those working in high-risk settings.
• Testing is recommended for people who are sick and have symptoms that worsen.

European health authorities are warning there may be an increase in Covid-19 infections in the coming months amid the spread of the new Omicron variant NB.1.8.1. or "Nimbus."


"We have what feels like a fairly standard suite of recommendations that are being repeated," Ajibola Omokanye, an ECDC respiratory viruses expert, told DW.

"But we remain watchful."

The 2024-2025 winter in the Northern Hemisphere has given experts like Omokanye good reason to be watchful.

Population immunity against SARS-CoV-2, the virus that causes Covid-19, is down in Europe, probably due to fewer Covid cases over the winter.

As a result, Omokanye said there may be an increase in infections over the European summer. This may include severe cases that require hospital treatment.

A need for ‘continued vigilance': ECDC expert advice

SARS-CoV-2 is becoming more endemic in communities but it is "still not a season pathogen, like influenza," said Omokanye.

Covid still appears to move and mutate in unpredictable ways and that "stresses the need for continued vigilance and not being complacent about SARS-CoV-2," said Omokanye.

"Just in the same way that we're not complacent about influenza or RSV."

Bangladesh has already seen deaths due to Covid in June. China and Singapore have also detected new cases of the respiratory disease.

Deaths in places like Bangladesh may be partly due to people's poor access to healthcare.

By comparison, Omokanye cited Canada, where Nimbus is dominant but without the same rates or severity of cases.

But it's not only a case of access to healthcare. "There are multiple factors. First, it's the timing of [a] variant's emergence," Omokanye said.

Another, he said, is that there could be a greater possibility for waning immunity where there's been low circulation for a long period of time.

With vaccination, there are also several important factors: Which vaccines are available in each country or region and "who they are given to and when," said Omokanye.

"The question is: are the vaccines being taken up by that proportion of the population where you see the most severe disease?"

Similarly, with healthcare systems and access to supportive treatment, localized differences may determine how seriously infections progress in a population.

"They all contribute to the picture of severe disease," said Omokanye.

What makes Nimbus different from other Omicron subvariants?

ECDC and the world health organization have classified Nimbus as a variant under monitoring (VUM) due to two specific spike mutations.

The spikes are the "prongs" that enable the virus to latch onto and infect human cells. They have regularly mutated since SARS-CoV-2 first emerged.

Spike protein mutations reduce the ability of human antibodies to neutralize an infection and others that enhance the virus' ability to evade human antibodies.

VUM is the lowest category in a system where the more severe stages are Variant of Interest and variant of concern.