What is the XEC virus? Latest facts about the new strain spreading in London

There’s been a lot of talk about the XEC virus in London lately, and if you’ve seen headlines saying it’s "more contagious" or "spreading fast," you’re not alone in wondering what’s really going on. The short answer: XEC is a new subvariant of the Omicron strain of SARS-CoV-2, the virus that causes COVID-19. It’s not a brand-new virus - it’s a mutated cousin of ones we’ve seen before. But its changes are enough to make it spread more easily than earlier versions, and that’s why public health teams in the UK are watching it closely.

Where did XEC come from?

XEC isn’t something that popped up out of nowhere. It’s a recombinant variant, meaning it formed when two different Omicron subvariants - XBB.1.5 and BA.2.86 - swapped parts of their genetic code while infecting the same person. This kind of mixing happens more often than people think, especially when lots of people are infected at once. The first confirmed cases of XEC showed up in the UK in late July 2025, and by early October, it had become the dominant strain in London, making up over 60% of new infections.

What makes XEC different isn’t that it causes worse illness - so far, it doesn’t seem to be more deadly than earlier strains. Instead, it’s better at slipping past immunity. Whether you got vaccinated, had a past infection, or both, your body’s defenses might not recognize XEC as easily. That’s why even people who thought they were protected are getting sick again.

What are the symptoms?

The symptoms of XEC are pretty similar to other recent COVID strains. Most people report:

• Sore throat
• Runny or stuffy nose
• Cough (often dry)
• Fatigue
• Headache
• Mild fever

Some people also feel muscle aches or lose their sense of smell or taste, but those are less common than with earlier versions of the virus. Unlike the Delta variant, which often led to serious lung issues, XEC mostly stays in the upper respiratory tract - which is why it spreads so easily through talking, coughing, or sneezing, but doesn’t usually land people in the hospital.

One key difference people are noticing: symptoms hit faster. Instead of taking 3-5 days to show up after exposure, many report feeling off within 24-48 hours. That makes it harder to stop the spread because people are contagious before they even realize they’re sick.

Is XEC more dangerous than other variants?

Based on data from Public Health England and the UK Health Security Agency, there’s no clear sign that XEC causes more severe disease. Hospitalization rates in London have stayed flat since XEC became dominant, even as case numbers rose. That’s likely because most people now have some level of immunity - either from vaccines, prior infections, or both.

That doesn’t mean it’s harmless. Older adults, people with weakened immune systems, and those with chronic conditions like diabetes or heart disease are still at higher risk. The biggest concern isn’t the virus itself - it’s how fast it moves through crowded places like offices, schools, and public transit. A single person with XEC can infect several others before they even know they’re sick.

How is London responding?

London’s public health teams aren’t imposing new lockdowns or mask mandates. Instead, they’re focusing on smart, targeted actions:

• Encouraging high-risk groups to get the updated 2025 autumn booster, which includes protection against XEC
• Boosting testing availability in GP clinics and pharmacies
• Recommending masks in crowded indoor spaces, especially during peak hours
• Working with schools to improve ventilation and offer rapid tests to students and staff

The UK government stopped free testing for the general public in 2023, but rapid antigen tests are still widely available for purchase at pharmacies. If you have symptoms, getting tested is the best way to know if it’s XEC - and whether you need to isolate to protect others.

What should you do if you think you have it?

If you’re feeling unwell with cold-like symptoms, here’s what works:

1. Take a rapid antigen test. These are accurate for detecting XEC if you have symptoms.
2. If it’s positive, stay home for at least 48 hours after your fever is gone and symptoms are improving.
3. Wear a mask around others for 5-7 days, even after you feel better.
4. Drink fluids, rest, and use over-the-counter meds like paracetamol if needed.
5. Call your doctor if you have trouble breathing, chest pain, or symptoms that get worse after a few days.

There’s no need to panic. Most people recover without medical help. But acting quickly helps protect vulnerable people around you - like grandparents, coworkers with health conditions, or new parents.

Are vaccines still effective against XEC?

Yes - but only if you’ve had the latest shot. The 2025 autumn booster, released in September 2025, was specifically updated to match XEC and other circulating strains. People who got this booster are 65-70% less likely to get infected and 85% less likely to be hospitalized compared to those who haven’t been boosted in over a year.

Older vaccines - like the ones from 2022 or 2023 - offer much less protection against XEC. If you haven’t had a booster since before 2024, your protection has dropped significantly. That’s why health officials are urging everyone over 65, pregnant women, and those with chronic illnesses to get the new shot as soon as possible.

Even if you’ve had COVID multiple times, the booster still helps. It doesn’t just prevent infection - it lowers your risk of long-term symptoms like brain fog, fatigue, or heart issues that can last months.

What’s next?

Viruses keep changing. Scientists are already tracking new mutations that could emerge from XEC. The next variant might be called XEC.2 or something else entirely. But the tools we have now - vaccines, tests, and simple hygiene - still work.

The key is staying informed without being alarmed. XEC isn’t a mystery virus. It’s a reminder that COVID-19 is still here, but we’re no longer helpless against it. The best defense isn’t fear - it’s knowing what to do and acting on it.