Here’s what we know about the new COVID-19 variants, 'Stratus' and 'Nimbus,' which have become widespread in the United States.
As fall settles in, the United States is experiencing a surge in COVID-19 cases, driven by the spread of two new variants: Stratus (XFG) and Nimbus (NB.1.8.1).
These variants have quickly gained prominence, with Stratus now being the dominant strain in circulation.
Although experts say they do not pose a greater threat than previous strains, they have brought in new symptoms and greater transmissibility.
Rise in Cases and Strain on Hospitals
COVID-19 cases have been spiking across several states, including California, Connecticut, and North Carolina, according to the latest data from the Centers for Disease Control and Prevention.
As of mid-September, many areas report high levels of viral activity, especially in wastewater, signaling continued community spread.
Hotspots have been particularly concentrated in the West and South, with significant rises in Alabama, Utah, and Nevada.
While the severity of infections appears to be lower than during earlier waves, many vulnerable groups, such as the very young and elderly, have been admitted to the hospital.
What We Know About Stratus and Nimbus Variants
The World Health Organization (WHO) explained that the Stratus variant (XFG), which emerged in Southeast Asia earlier this year, is a recombinant strain formed by the fusion of two Omicron subvariants, LF.7 and LP.8.1.2.
According to Dr. William Schaffner, an infectious disease expert at Vanderbilt University, Stratus is highly transmissible but does not appear to cause more severe illness than earlier Omicron strains.
However, its hybrid nature may make it better at evading immunity, both from prior infections and vaccinations, which may contribute to its ability to spread so fast.
Nimbus, also known as NB.1.8.1, is another variant in circulation, though it has been overshadowed by Stratus in recent months.
Still, experts like Dr. Albert Ko, a professor of public health at Yale, suggest both variants share similarities in their ability to escape immunity, making reinfections more common.
However, neither variant is believed to cause more severe illness compared to previous Omicron strains.
While COVID symptoms are generally consistent with earlier variants, there have been anecdotal reports suggesting that Stratus and Nimbus may cause more throat-related symptoms, including a “razor blade” sore throat or hoarseness, per BBC News.
These symptoms, alongside the usual fatigue, cough, and congestion, have made the variants hard to distinguish from the common cold or flu.
Patients may also experience headaches, fever, shortness of breath, and in some cases, a new loss of taste or smell.
Vaccines and Protection Against New Variants
Despite the rise of these new variants, vaccines remain highly effective at preventing severe illness and death.
Dr. Schaffner has reassured the public that existing vaccines are expected to provide protection against Stratus and Nimbus, and remain the most effective way to reduce the risk of severe outcomes.
Both the CDC and WHO recommend that individuals at high risk - such as older adults, those who are immunocompromised, and people with underlying health conditions - get vaccinated, especially as the colder months approach.
Health professionals have also emphasized the importance of staying home if feeling unwell, wearing face coverings when necessary, and practicing good hygiene to help reduce the spread of the virus.