COVID is Everywhere (Again) in the Bay Area. What to Know About the Latest XFG 'Stratus' Variant

Looking for information about the FDA’s limited approval of 2025-26 COVID vaccines? Read what we know about who can get an updated COVID shot this year.

Updated Aug. 27

If it feels like several people you know are complaining of feeling sick with what they assume is an “awful summer cold” — perhaps with an especially sore throat — there’s a good chance it could be COVID-19.

Again.

COVID-19 levels in Bay Area wastewater have gone up 50% in August compared to the month before, and are still far exceeding the winter peak, according to Stanford’s WastewaterSCAN team, which monitors coronavirus presence in human sewage. And according to the California Department of Public Health’s own wastewater tracking, infections statewide numbers also surpassed winter highs back in July.

There’s also a new top variant out there, XFG or “Stratus.” This now makes up 82% of variants detected in Bay Area wastewater, according to Stanford. People infected with Stratus often report a scratchy, hoarse throat that’s easily mistaken for allergies.

The previous top variant,  NB.1.8.1 or “Nimbus” — known for a particularly nasty sore throat that earned it the nickname “razor blade throat” — now only makes up 5.2% of variants in local wastewater, according to Stanford. So if you suspect you’ve got COVID-19, right now it’s more likely to be the XFG strain.

So, what do you need to know about the symptoms of XFG? What’s the COVID-19 incubation period in 2025, how long should you isolate and where can you still find a free COVID-19 test? And if you’re unfortunate enough to suffer painful throat symptoms, what can you do to ease your symptoms?

Keep reading for everything you need to know about the new Stratus variant or jump straight to:

• What are the symptoms of XFG (Stratus)?
• If I’m exposed, how long before I get sick with COVID in 2025?
• Do the latest COVID-19 vaccines work against the new variant, and should I get another shot?
• Where can I still find free COVID-19 tests?

And if you’re reading this because you suspect you have COVID-19:

• How long should I isolate with COVID-19 in 2025?
• I tested negative. Can I trust my antigen kit?
• How can I soothe my painful sore throat if I’m infected?

What is XFG, and is it worse than previous variants?

XFG or Stratus is currently the most prevalent COVID-19 subvariant in the Bay Area at 82%, according to WastewaterSCAN.

(Unfortunately, you won’t be able to use the Centers for Disease Control and Prevention’s own variant tracker to see the top variants nationwide, as it was last updated in June.)

Like Nimbus before it, Stratus is absolutely more transmissible — that is, more contagious and more easily caught — than previous variants, said Dr. Peter Chin-Hong, an infectious disease expert at UCSF. That’s how a new variant ends up beating its siblings and “rising to the top of the charts,” he said.

XFG’s particular “superpower,” said Chin-Hong, “is that it has four mutations in the spike protein, which make it just a little bit more transmissible than the previous variants.”

But there’s no evidence that Stratus causes more serious disease, Chin-Hong said, echoing the World Health Organization’s June briefing designating it a “variant under monitoring.”

Despite this, new variants like Stratus will still cause more people to go to the hospital with COVID-19, he said, “because if it’s fueling more people getting it, some of those people are going to be more vulnerable.”

What are the symptoms of the new XFG Stratus COVID-19 variant?

Chin-Hong confirmed that no surprising wild card symptoms have yet been reported for XFG — they’re the same COVID-19 symptoms you’re used to hearing about from previous variants.

That said, Chin-Hong noted that doctors are hearing that people infected with Stratus report suffering from scratchy, hoarse throats that resemble allergy symptoms. And previously with Nimbus, patients particularly complained about the very painful throat symptom that earned NB.1.8.1 the unfortunate nickname of “razor blade throat.”

Why is Stratus — and Nimbus before it —  causing such throat symptoms? They’re descendants of the omicron variant that first emerged in 2021, and “I think omicron in general prioritizes the upper respiratory tract instead of the getting into the lungs as much,” Chin-Hong said.

One 2022 study from the United Kingdom found that a higher proportion of patients — up to 70% of those studied — reported sore throats when infected with the omicron variant compared with earlier variants. Or as Chin-Hong put it, “a lot of the action is at the throat level.”

As with previous variants to reach the Bay Area, Chin-Hong noted that more people also now appear to experience more non-respiratory symptoms like diarrhea, nausea and vomiting when they get COVID-19 — gastrointestinal symptoms that folks can often initially dismiss as being unrelated to the virus.

According to the CDC, this is the full list of the possible symptoms of COVID-19:

• Fever or chills
• Cough
• Shortness of breath or difficulty breathing
• Fatigue
• Muscle or body aches
• Headache
• New loss of taste or smell
• Sore throat
• Congestion or runny nose
• Nausea or vomiting
• Diarrhea.

Remember, you might have a combination of these symptoms or just one. They might be mild or feel more severe. But if you’re experiencing any of these, take a COVID-19 test (more on this below).

OK, so how can I soothe my sore throat if I’m infected?

For any kind of sore throat, it might be tempting to focus on topical medicine for your throat itself. But in general, systemic therapies — treatments which enter through your bloodstream like Advil and affect your whole body — “are better than topical ones,” Chin-Hong said. His recommendations:

Ibuprofen and acetaminophen

Ibuprofen (like Advil) is better than acetaminophen (like Tylenol) in this case, he said, although you should check with your health provider if you have other medical conditions which might make taking ibuprofen unsafe. If your throat hurts too much to swallow a pill, you can consider liquid versions of these drugs, but make sure you use the right dose depending on age, Chin-Hong said. And if you’re using a combination cold remedy like Nyquil, be aware it might already contain ibuprofen or acetaminophen — and be careful not to accidentally double-dose.

Topic remedies

You could try warm remedies like chicken soup, broth, lemon tea, honey or cold ones like popsicles, ice cream or ice chips. The upside of these treatments is the immediate relief they can bring, but they might also not last as long. You could also try gargling salt water, “which may loosen mucus” Chin-Hong said, or sucking lozenges with menthol or a mild anesthetic like benzocaine.

Environmental treatments to try 

Chin-Hong also recommends:

• Stay hydrated
• Get your rest
• Don’t smoke or expose yourself to smoke
• Consider a humidifier, as dryness may make your symptoms worse.

And you should consider seeking medical attention if your symptoms last longer than a week, if your sore throat is very severe, and if you begin drooling or become unable to eat or drink, Chin-Hong said.

What are the current COVID-19 cases in the Bay Area right now?

Actual “COVID cases” — that is positive test results — are no longer tracked as closely by local and state public health bodies. In the absence of widespread up-to-date data on positive test results, monitoring the presence of the coronavirus in human sewage has become an increasingly important way to gauge the levels of COVID-19 spread in a particular area. This is because if you have COVID-19, the virus will show up in your feces soon after you’re infected.

Despite recent increases in COVID-19 levels in the Bay Area’s wastewater, Amanda Bidwell from Stanford’s WastewaterSCAN team said that average concentrations are still lower than this time last year when the Bay Area experienced a summer surge. However, the Bay Area’s wastewater sites monitored by Stanford are currently in the “high” category, and have kept rising over the last three weeks.

You can check the COVID-19 levels in your own county’s wastewater according to WastewaterSCAN’s monitoring:

San Francisco | Alameda | San Mateo | Santa Clara | Contra Costa | Solano | Marin | Sonoma | Napa

Is the latest COVID-19 vaccine still effective against the new variants?

Yes: The COVID-19 vaccine that rolled out in August 2024 is effective against XFG, or Stratus, Chin-Hong said, because like Nimbus it’s a descendant of JN.1, which last year’s vaccines were based on.

If you didn’t get your COVID-19 shot in the fall, Chin-Hong has a message: Go get one now, particularly if you plan to travel this summer.

Not only will your protection last roughly a year, he said, “getting it now if it’s being paid for would help that person navigate through what we might see in the summer, but also later on in the year if rules change” — referring to the widespread uncertainty about how President Donald Trump’s administration might further change the U.S.’s vaccine policies.

Currently, the CDC recommends the COVID-19 vaccine for most adults 18 and older, which means that most health insurance companies should cover the costs for people with insurance.

I think I was exposed or have symptoms. When should I take a COVID-19 test?

Step 1: Know about updated incubation times 

If you’ve heard that incubation times for the virus are getting shorter — that is, the amount of time between getting exposed to COVID-19 and testing positive — it’s true. People are testing positive more quickly than they were in 2020, when the average incubation period was five to seven days, because it has changed with each new variant, Chin-Hong said.

Three days is a common period of time between exposure and getting sick, Chin-Hong said, and given this trend, it makes sense to take a COVID-19 test as early as two days after exposure if you’re already having symptoms.

Step 2: Don’t trust a negative early COVID-19 test

If your first test is negative, you should absolutely test again the next day if symptoms persist — and again after that if you’re still negative.

Here’s why you can’t necessarily trust a negative at-home COVID-19 test in 2025: While incubation times have gotten shorter, doctors are seeing people take longer to get a positive test, Chin-Hong said, and that’s probably more to do with how much quicker someone with COVID-19 might develop symptoms in 2025 than they would have done in 2020.

As a reminder, those symptoms are the sign that your body’s immune system is mounting a response to an invading virus. Back at the start of the pandemic, by the time you developed COVID-19 symptoms and took a test, it would probably already be positive.

But at this stage of the pandemic, “we likely have more immune cells circulating that can recognize the enemy, so it ‘sounds the alarm’ quicker [and] people might feel something faster than in the old days,” Chin-Hong said.

Dr. Abraar Karan, an infectious disease physician and researcher at Stanford University, also put it this way for NPR in 2024: “With our immune systems primed, the body’s response [now] comes much more quickly than it would have back in 2020 when SARS-CoV-2 was a novel pathogen.”

And because many of us take a COVID-19 test when we start to feel sick, we might actually be testing way too early for an at-home antigen kit to successfully detect enough virus inside us.

The bottom line: If you’re testing because you’ve started feeling unwell, don’t assume a negative result means you don’t actually have COVID-19. Play it safe, stay home as much as you can and wear a well-fitted mask if you can’t. Take another antigen test 48 hours later, Chin-Hong said. You can also seek out a PCR test, which is more sensitive.

Step 3: Make sure your COVID-19 test hasn’t expired

Those COVID-19 tests you might have in a drawer may be approaching their expiration date if they haven’t already passed it. And an expired test could give you an unreliable result.

You can check the FDA’s list of antigen test types to see whether the box you’re holding has had its shelf life extended by the manufacturer. The FDA said that if a test’s shelf life has been extended, it’s because the manufacturer has given the agency enough “data showing that the shelf-life is longer than was known when the test was first authorized.” (In other words, it’s still OK to use that test.)

Another tip from Chin-Hong: “A quick and dirty way” to know if you’re using a functional COVID-19 test is to make sure the control line turns positive. If that doesn’t happen, “that means the test is probably not working,” he warned.

If I test positive, how long do I have do isolate with COVID-19 in 2025?

In March 2024, the CDC officially revised their national COVID-19 isolation guidance, saying that COVID-positive people could now return to work or regular activities once “symptoms are improving overall” and they’ve been fever-free for at least 24 hours without use of a fever-reducing medication.

Read more about current isolation guidance for COVID-19.

If you’ve been infected, consider asking your health provider for the COVID-19 medication Paxlovid, an antiviral treatment in pill form that is still available free by prescription in California. Read more on requesting a prescription for Paxlovid, with or without health insurance.

Where can I still find a free COVID-19 test?

Good question.

Finding a quick, free COVID-19 test — whether an at-home antigen test or a PCR test — has gotten progressively harder at this stage of the pandemic as more sites and services have been shuttered.

And visiting the White House site that once offered you free at-home COVID-tests through USPS will now greet you with an image of Trump superimposed over the headline “LAB LEAK: The True Origins of COVID-19,” as well as a page dedicated to the theory disputed by many scientists that the pandemic was caused by the coronavirus leaking from a government laboratory in Wuhan, China.

So, what do you do now if you don’t already have a supply of antigen tests for COVID-19 at home right now? Try the following:

Purchase a COVID-19 at-home antigen test at a pharmacy near you

The quickest option will also be one of the most expensive up-front: Purchasing an at-home antigen test at a nearby pharmacy. (Ideally, ask someone to purchase one for you so you don’t potentially expose other people at the pharmacy, and if you really have to go yourself, wear a well-fitted N95 mask to help lower the risk you pose to others.) These at-home test kits are usually around $20 for a pack of two.

If you have health insurance, you can request reimbursement from your health insurer for the cost of up to eight at-home tests per month, so don’t throw away your receipts.

Find a COVID-19 PCR testing site near you

PCR testing is more accurate than an antigen test. It’s more sensitive at picking up traces of the coronavirus in your body, but it may take longer to get your results than with an at-home test.

Currently, there are still some sites offering free COVID-19 testing around the state. Try visiting MyTurn.ca.gov/testing and applying the “Free Sites” filter from the drop-down menu. You can also find a health center near you and ask if they offer COVID-19 testing.

The CDC’s COVID-19 test locator is no longer operational.

If you have health insurance, you may be able to get a PCR test ordered by your health care provider with the costs covered. Having a test ordered by a provider is — usually — the only way to get your testing costs covered if you have Medicare, too.

If you have health insurance, contact your provider

If you’re insured through major Bay Area providers like Kaiser Permanente or Sutter Health, the easiest way to get a COVID-19 test may be to make an appointment through your provider.

Most providers offer sign-ups online through a member login and appointments can also be made by phone.

An earlier version of this story was originally published on June 26. KQED’s Lesley McClurg, Alexander Gonzalez and Brian Watt contributed reporting to this story.