By: Express Web DeskUpdated: October 3, 2025 09:29 AM IST 3 min readCommon symptoms for both the Nimbus and Stratus variants are largely similar to the previous Covid strains.Cases of the “Nimbus” (NB.1.8.1) and “Stratus” (XFG) Covid-19 variants are rising globally, now dominating infection trends across major regions like Asia, Europe, and the US. While both variants are highly transmissible and show some immune evasion, current developments suggest their severity is not greater than the previous Covid strains, though vulnerable groups remain at increased risk.What Are These Variants?“Nimbus” (NB.1.8.1) was first identified in China in early 2025 and quickly spread worldwide, now representing a significant share of cases in several countries. According to Professor T Ryan Gregory from the University of Guelph in Canada, the variant was named after a type of cloud.“Stratus” (XFG), named after another tpe of cloud, is a hybrid Omicron sub-lineage that emerged in Southeast Asia. It has similarly become dominant, accounting for nearly 60% of global cases by late 2025.Transmission and SpreadBoth variants exhibit features that help them circulate rapidly:Nimbus binds more efficiently to human ACE2 receptors, making it up to 2.5 times more transmissible than some prior Omicron subvariants.Stratus spreads faster by evading immune responses, though it is less efficient at cell entry than Nimbus.In the UK, Stratus accounts for 63% of recent cases, with Nimbus at 25%, as per the UK Health Security Agency (UKHSA).Both variants are implicated in ongoing spikes in North America, Europe, and Asia, including notable outbreaks in the US and India.What are the symptomsCommon symptoms for both variants are largely similar to the previous Covid strains. However, there are a few subtle changes.The Nimbus variant, for example, frequently causes a sharp, “stabbing” sore throat, intense fatigue, mild cough, nasal congestion, fever, and digestive distress for some.The Stratus variant displays typical Covid symptoms, such as sore throat, cough, runny nose, fever, headache, and muscle aches. In some cases, hoarseness and a raspy voice was reported in some patients the BBC stated.Story continues below this adAlthough the severity is not markedly high in these patients compared to earlier variants, aged patients, especially those with chronic conditions, and the unvaccinated remain at higher risk for complications.Severity and Vaccine ResponseThe WHO has not found evidence of increased severity for either Nimbus or Stratus, though both carry mutations aiding immune evasion.The current lot of vaccines, which includes JN.1-targeted shots, are likely to prevent severe disease. However, the efficacy against symptomatic infection ranges between 19% and 49%.Experts warn that periodic Covid waves are likely, especially as immunity from vaccination and past infection wanes globally, and highlight the need for high-risk groups to continue precautionary measures.Story continues below this adImpact in IndiaWhile a few cases have reportedly been seen in India and the variants are under monitoring, experts say they pose no more threat than the previous variants that we saw in India. The vaccines and booster shots available in the country should provide immunity from these variants.Severe cases may require hospitalisation. Doctors advise avoiding crowded spaces, proper hygiene, and use of masks.Stay updated with the latest - Click here to follow us on Instagram© IE Online Media Services Pvt LtdTags:COVID-19