Symptoms of Nimbus COVID-19 variant: Watch out for sore throat, body-ache, fever, more

The new COVID-19 variant NB.1.8.1, known as Nimbus, is causing concern due to its subtle symptoms and high transmission rate. According to the World Health Organisation, recognising early signs and adopting preventive habits can reduce risk. Here’s what you need to know to keep your home and health protected.

Namita S Kalla

June 23, 2025 / 12:58 IST

Symptoms of Nimbus Covid-19 variant: Early reports show most patients complain of an overwhelming tiredness that appears without physical exertion. Unlike regular fatigue, it lingers for days even after full rest (Image: Canva)

The latest strain of COVID-19, officially named NB.1.8.1 and informally called Nimbus, has recently been flagged by health authorities due to its rising presence in multiple countries. While not as severe as previous waves, experts caution that its mild onset symptoms can delay testing and lead to unintentional spread.

According to the World Health Organization (WHO), Nimbus is a new version of the Omicron strain of the virus that causes Covid-19. It’s also called NB.1.8.1. The WHO is keeping an eye on it, but says the overall risk to the public is low right now.

Moreover, the Centers for Disease Control and Prevention (CDC) in the US says that Nimbus is now behind 37 percent of Covid cases in America. So far, it's spreading, but doesn’t seem to cause worse symptoms than earlier types. Which means nimbus is a version of Covid worth watching, but there’s no need to panic. Stay updated, take your vaccines, and follow basic hygiene practices.

Also read | NB.1.8.1 COVID-19 variant cases and symptoms: 7 things to know about this new COVID-19 strain

Symptoms and protection tips for NB.1.8.1 Nimbus:

Recognise unusual fatigue: Early reports show most patients complain of an overwhelming tiredness that appears without physical exertion. Unlike regular fatigue, it lingers for days even after full rest.

Watch for low-grade fever: Nimbus often begins with a persistent low fever between 99–100°F. It’s easy to ignore, but when paired with tiredness or headache, it's worth getting tested.

Notice a scratchy throat: Rather than a painful sore throat, many experience a dry or tickly sensation that worsens over time. It may come with mild hoarseness or coughing.

Check for body aches: Even without a high fever, Nimbus may cause muscular aches and joint stiffness, especially in the back and legs. This is often confused with routine exhaustion.

Be aware of sinus-like pressure: Some patients report a blocked nose or sinus pressure without a runny nose. If this is paired with fatigue, it may signal a developing infection.

Also read | How to protect yourself from norovirus, COVID-19, flu and RSV

Mask up in public spaces: Health experts still recommend wearing a well-fitted mask, especially indoors or on public transport, even if local mandates have eased.

Revisit hand hygiene: Frequent handwashing and avoiding face-touching are simple but effective ways to prevent the spread of respiratory viruses like Nimbus.

Improve indoor air flow: Good ventilation is critical. Open windows when possible or use HEPA filters at home and work to reduce virus particles in the air.

Prioritise booster vaccinations:

COVID-19 Vaccine

Frequently Asked Questions

How does a vaccine work?

A vaccine works by mimicking a natural infection. A vaccine not only induces immune response to protect people from any future COVID-19 infection, but also helps quickly build herd immunity to put an end to the pandemic. Herd immunity occurs when a sufficient percentage of a population becomes immune to a disease, making the spread of disease from person to person unlikely. The good news is that SARS-CoV-2 virus has been fairly stable, which increases the viability of a vaccine.

How many types of vaccines are there?

There are broadly four types of vaccine — one, a vaccine based on the whole virus (this could be either inactivated, or an attenuated [weakened] virus vaccine); two, a non-replicating viral vector vaccine that uses a benign virus as vector that carries the antigen of SARS-CoV; three, nucleic-acid vaccines that have genetic material like DNA and RNA of antigens like spike protein given to a person, helping human cells decode genetic material and produce the vaccine; and four, protein subunit vaccine wherein the recombinant proteins of SARS-COV-2 along with an adjuvant (booster) is given as a vaccine.

What does it take to develop a vaccine of this kind?

Vaccine development is a long, complex process. Unlike drugs that are given to people with a diseased, vaccines are given to healthy people and also vulnerable sections such as children, pregnant women and the elderly. So rigorous tests are compulsory. History says that the fastest time it took to develop a vaccine is five years, but it usually takes double or sometimes triple that time.

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