Health

8 Shocking Facts About the New COVID-19 Variants “Nimbus” and “Stratus”

2025-06-16

Author: Arjun

COVID-19 might not dominate the news anymore, but it’s far from finished – and it’s changing more than ever! The World Health Organization (WHO) is currently tracking six 'variants under monitoring,' including the newly emerged NB.1.8.1, affectionately dubbed "Nimbus" by a dedicated team of researchers and citizen scientists. This group previously labeled variants like Kraken, Centaurus, and Eris.

Another rising star in the viral world is XFG, nicknamed "Stratus." Although it’s not yet on WHO’s monitoring list, it’s making waves.

1. Rapid Spread, But No Increase in Severity

Since its emergence in January 2025, Nimbus has rapidly disseminated throughout Asia and beyond, rising from 2.5% to 11% of sequenced cases in just one month! Despite this surge, there’s no evidence that it causes more severe illness than its counterparts. In fact, WHO’s recent evaluation states that Nimbus doesn’t pose a higher public health risk than other Omicron variants.

Meanwhile, Stratus is also gaining traction. As of late May, it accounted for 25% of cases in Europe and is on the rise in India.

2. Nimbus Isn’t a Harry Potter Reference!

The term "Nimbus" actually refers to a type of cloud, not a broomstick or a sci-fi spacecraft! Prof. T. Ryan Gregory from the University of Guelph explains that this is the first unofficial nickname for a COVID variant in nearly two years, marking a significant recognition in the viral landscape.

3. They’re Genetic Mash-Ups!

Nimbus and Stratus are not your average viruses. Both are hybrids formed through genetic recombination of multiple Omicron strains. Nimbus features seven new mutations in its spike protein, while Stratus carries four. This unique genetic makeup helps them to thrive!

4. Nimbus Infects Cells Like a Pro!

Studies suggest that Nimbus binds exceedingly well to the human ACE2 receptor that SARS-CoV-2 uses to invade cells. It demonstrates extraordinary infectivity, potentially being 2.5 times more effective than the current leading COVID variant.

5. Stratus Has Tricks Up Its Sleeve!

Stratus flaunts mutations thought to boost its ability to evade the immune system, making it tricky for our body to neutralize. However, its weaker binding to the ACE2 receptor might limit its infectious power unless it picks up more mutations.

6. Vaccines Still Offer Protection!

Lab tests indicate that existing vaccines still have a strong chance of protecting against Nimbus and Stratus. The reduction in antibody effectiveness is minimal, so fully vaccinated individuals, especially those with updated boosters, should still be shielded from severe illness.

7. New Symptoms to Watch Out For!

While the symptoms are similar to other Omicron variants, UK doctors warn about specific signs linked to Nimbus, such as a "razor blade" feeling in the throat and gastrointestinal issues. Indian physicians have also noted that a hoarse voice could be common among patients.

8. Regarding Public Health Risks!

Currently, NB.1.8.1 is classified as a Variant Under Monitoring by the WHO, reflecting a low public health risk. Stratus isn’t on the WHO’s radar yet, but rest assured, it’s still under careful scrutiny. All emerging variants are subject to routine surveillance for their potential impact on public health.