Feeling under the weather lately, perhaps with what feels like an unusually harsh sore throat? If you or someone you know is complaining of an “awful summer cold,” there’s a significant chance it could actually be COVID-19 – fueled in part by a new subvariant nicknamed “Nimbus.”
While overall COVID levels in some areas might be lower than in previous years, indicators like wastewater surveillance show the virus is still circulating and slowly increasing in places like the Bay Area. The main driver behind this recent uptick is a new subvariant known officially as NB.1.8.1, which has quickly earned the colloquial moniker “Nimbus.”
One symptom reported by many infected with this strain is a particularly severe sore throat, earning Nimbus the unpleasant nickname “razor blade throat.”
So, what exactly is the Nimbus variant? What symptoms should you watch for, especially that painful throat? How long does it take to get sick after exposure in 2025, and when should you test? And if you do get hit with “razor blade throat,” what can you do for relief? Read on for the latest information.
What is the Nimbus Variant (NB.1.8.1)?
NB.1.8.1, or “Nimbus” (a nickname coined by evolutionary biologist T. Ryan Gregory), is the latest descendant of the Omicron lineage, specifically deriving from the XVD.1.5.1 recombinant variant. First detected in China in January 2025, it quickly spread globally. The World Health Organization (WHO) designated it a “variant under monitoring” in May 2025, signaling its potential for increased spread.
Nimbus has rapidly become the most prevalent COVID-19 subvariant in the United States. Estimates from the Centers for Disease Control and Prevention (CDC) show it accounting for approximately 43% of cases nationwide. In California, state health officials reported Nimbus made up a significant 55% of circulating virus in June, a sharp rise from just 2% in April. Bay Area data from Stanford’s WastewaterSCAN confirms its dominance, accounting for over 48% of variants detected at sites like San José.
Experts like Dr. Peter Chin-Hong, an infectious disease expert at UCSF, note that Nimbus is significantly more transmissible (contagious) than previous variants. This increased transmissibility is likely due to genetic changes, particularly in its spike protein, which may help the virus attach more easily to cells.
Despite being highly contagious, there is currently no strong evidence that NB.1.8.1 causes more severe disease at an individual level compared to other recent strains. However, because it’s fueling more infections, it inevitably leads to a rise in the total number of people becoming sick and needing hospitalization, particularly among vulnerable individuals.
Symptoms of the Nimbus Variant: Beyond ‘Razor Blade Throat’
The symptoms associated with the Nimbus variant are largely the same broad range of symptoms seen with previous COVID-19 strains. However, one symptom stands out due to its reported intensity: a very painful sore throat.
This severe sore throat has been widely described by patients as feeling like swallowing glass shards, being burned by acid, or, most vividly, having a “razor blade throat.” Reports from China also suggest that this intense throat pain, alongside coughing, might be more prevalent with Nimbus compared to some earlier strains.
Why might Omicron descendants like Nimbus cause such severe throat pain? Experts believe these variants tend to prioritize infection of the upper respiratory tract (throat, nose, airways) rather than primarily targeting the lungs as much as earlier variants did. A 2022 study from the United Kingdom found that a higher proportion of patients with the Omicron variant (up to 70%) reported sore throats compared to those with earlier variants.
In addition to the prominent sore throat, other common symptoms include:
Fever or chills
Cough
Shortness of breath or difficulty breathing
Fatigue
Muscle or body aches
Headache
New loss of taste or smell
Congestion or runny nose
Some people infected with recent variants, including Nimbus, also appear to experience more non-respiratory symptoms like nausea, vomiting, and diarrhea, which can sometimes be initially mistaken for unrelated issues.
Remember, you might experience just one or a combination of these symptoms, and they can range from mild to severe.
Soothing ‘Razor Blade Throat’: Relief Measures
When dealing with an intensely painful sore throat like the one associated with Nimbus, symptom relief is key. While topical treatments can offer immediate comfort, systemic therapies that work through your bloodstream tend to be more effective overall, according to infectious disease experts like Dr. Chin-Hong.
Medical & Over-the-Counter Options:
Oral Pain Relievers: Ibuprofen (like Advil) is often preferred over acetaminophen (like Tylenol) for its anti-inflammatory properties that can help with throat swelling and pain. Check with your healthcare provider, especially if you have underlying medical conditions. If swallowing pills is too painful, liquid formulations are an option (ensure correct dosing for age). Be mindful of combination cold medicines that may already contain these ingredients to avoid double-dosing.
Lozenges and Sprays: Lozenges containing menthol or mild anesthetics like benzocaine can provide temporary topical relief. These are generally recommended for individuals over the age of 4.
Salt Water Gargle: Gargling with warm salt water may help loosen mucus and can be soothing.
Home Remedies and Supportive Care:
Warm Liquids: Sipping warm broth, tea with honey (for those over 1), or warm water can be comforting.
Cold Items: Sucking on ice chips, popsicles, or even ice cream can numb the throat temporarily and provide relief.
Stay Hydrated: Drinking plenty of fluids is crucial for overall recovery and keeping throat tissues moist.
Rest: Allow your body time to fight the infection.
Avoid Irritants: Do not smoke, and avoid exposure to smoke or other irritants that could worsen throat pain.
Use a Humidifier: Keeping the air moist, especially at night, can help prevent dryness that exacerbates throat irritation.
When to Seek Medical Attention:
While most viral sore throats improve with time and supportive care, seek medical attention if your severe sore throat lasts longer than a week, is extraordinarily severe, or if you experience difficulty breathing, become unable to eat or drink fluids, or begin drooling. These could indicate a more serious issue requiring professional evaluation.
Incubation Period & When to Test in 2025
The incubation period for COVID-19 – the time between exposure and symptom onset or testing positive – has generally shortened since the beginning of the pandemic. While it was typically 5-7 days in 2020, experts now commonly observe people developing symptoms and potentially testing positive around three days after exposure.
Given this shorter timeframe, if you’ve been exposed or start experiencing symptoms, it makes sense to test as early as two days after exposure if symptoms are present.
Don’t Trust an Early Negative Antigen Test:
A key point about testing in 2025 is that a negative result on an at-home antigen test, especially early in your symptoms, doesn’t necessarily mean you’re not infected. Due to prior immunity (from vaccination or previous infection), your body’s immune system might mount a response more quickly, causing symptoms to appear before the viral load is high enough for an antigen test to detect.
If you test negative on an antigen test but still have symptoms or suspect exposure, it is crucial to test again 48 hours later. A second test (or even a third) is much more likely to catch the virus if you are indeed infected. PCR tests are more sensitive and can detect lower viral loads, but results may take longer.
Also, make sure your COVID-19 test kit hasn’t expired. Manufacturers have extended the shelf life of many tests, and you can check the FDA’s website for an updated list. A quick way to verify a test is working is to ensure the control line appears correctly.
Are Current Vaccines Effective Against Nimbus?
Yes, the updated COVID-19 vaccine that rolled out in August 2024 is effective against the Nimbus variant. This vaccine was designed to target JN.1, and Nimbus is a descendant of that lineage, meaning the vaccine offers protection against NB.1.8.1.
Health experts recommend staying up-to-date with your COVID-19 vaccination. If you haven’t received your fall 2024 shot, getting it now provides protection that typically lasts about a year and is particularly recommended ahead of summer travel or potential future waves.
It’s worth noting that the landscape of vaccine recommendations has recently shifted at the federal level. In May 2025, the CDC altered its long-standing recommendations for healthy children and pregnant women, moving towards recommending parents consult a healthcare provider for children and offering “no guidance” for pregnant individuals. These changes, directed by the Department of Health and Human Services, have faced strong criticism from major medical organizations (like the American College of Obstetricians and Gynecologists and the American Medical Association) who emphasize the continued importance of vaccination for these groups based on scientific evidence showing reduced risks of severe outcomes and complications. Some states, including California, Oregon, and Washington, have publicly stated they will continue to follow science-based recommendations and maintain vaccine access, advising vaccination for everyone aged 6 months and older. This evolving policy environment highlights the importance of consulting with trusted healthcare providers about current recommendations and access.
Finding COVID-19 Tests in 2025
Finding readily available, free COVID-19 tests has become more challenging as pandemic response efforts have scaled back. The White House site for free mail-order tests and the CDC’s test locator are no longer operational.
If you need a COVID-19 test, here are some options:
Purchase At-Home Tests: At-home antigen tests are available for purchase at most pharmacies. Costs typically range around $20 for a pack of two. If you have health insurance, you can likely request reimbursement for the cost of up to eight tests per month, so keep your receipts. Consider having someone pick up tests for you if you are symptomatic.
Find PCR Testing Sites: Some sites still offer free PCR testing. You may be able to find these using state-specific resources like MyTurn.ca.gov/testing (apply the “Free Sites” filter) or by contacting local health centers.
Through Your Health Provider: If you have health insurance (including Medicare), arranging a test through your healthcare provider (like Kaiser Permanente or Sutter Health in the Bay Area) is often the easiest route and is typically required for cost coverage. Check your provider’s website or call them to schedule.
The Nimbus variant and its signature “razor blade throat” are a reminder that COVID-19 is still circulating and evolving. Staying informed about current symptoms, understanding testing best practices, and staying up-to-date with vaccination are key steps to navigate the pandemic landscape in 2025.
