The XEC variant of SARS-CoV-2 has rapidly increased in prevalence worldwide since its emergence in mid-2024, becoming a significant player in the evolving landscape of COVID-19 variants1 . This recombinant strain, derived from two Omicron sublineages, has shown a growth advantage over other variants, raising questions about its impact on public health and vaccine effectiveness2 . Understanding the current status of XEC in the United States, its symptoms, and differences from previous strains is crucial for ongoing pandemic management3 .
Current XEC Variant Status in the US
XEC is a recombinant SARS-CoV-2 variant formed from the genetic merging of two Omicron sublineages, KP.3.3 and KS.1.1, both descendants of the JN.1 variant4 5. First identified in Germany in June 2024, XEC has since spread globally, with sequences reported from over 50 countries1 . It has demonstrated a significant increase in prevalence, accounting for approximately 36.8% of global SARS-CoV-2 sequences by late November 2024, marking it as the only variant under monitoring (VUM) with consistent growth across multiple World Health Organization (WHO) regions1 .
In the United States, XEC's presence has been notable but data on state-level prevalence remain limited. As of late 2024, XEC was responsible for an estimated 14–22% of COVID-19 cases nationally, with its prevalence increasing while the previously dominant KP.3.1.1 variant showed a decline6 . By early December 2024, XEC had been detected in at least 25 states, and by the winter of 2024–2025, it became the most common strain in the U.S., accounting for about 45% of infections3 . However, as of September 2025, no peer-reviewed or government sources have provided detailed state-level case data for XEC7 8.
XEC's rapid spread is attributed to its recombinant nature, which combines genetic segments from two distinct Omicron subvariants. This recombination may confer a fitness advantage, allowing XEC to outpace other variants in transmissibility2 . Laboratory studies estimate that XEC's effective reproduction number (R8) is approximately 1.13 times higher than that of KP.3.1.1, supporting its competitive edge in viral spread1 .
“One reason for the concern is that XEC has moved quickly enough to outpace the growth of all other SARS-CoV-2 variants in a few areas in Europe.”3
The variant carries several key spike protein mutations, including T22N and Q493E, which are associated with increased transmissibility and enhanced immune evasion, respectively2 1. These mutations may reduce the neutralizing ability of antibodies generated by previous infections or vaccinations, although the extent of immune escape is considered limited1 .
Despite its growth, the WHO has assessed the overall public health risk posed by XEC as low, given the lack of evidence for increased disease severity compared to other Omicron subvariants1 . The variant's rise coincides with the availability of updated COVID-19 vaccines for the 2024025 season, which are designed to target prevalent strains including JN.1 and KP.2, and are expected to provide substantial protection against severe disease caused by XEC6 1.
Public health measures remain critical in controlling XEC's spread, especially during the winter months when respiratory infections typically surge. These measures include vaccination, testing, mask-wearing in crowded indoor settings, and avoiding close contact with sick individuals9 . The Centers for Disease Control and Prevention (CDC) continues to monitor variant proportions through genomic surveillance, although recent reductions in sequencing data have limited the precision of variant prevalence estimates9 .
| Variant | Approximate Global Prevalence (%) | Trend | Notes |
|---|---|---|---|
| XEC | 14 37 | Increasing | Recombinant of KP.3.3 and KS.1.1 |
| KP.3.1.1 | 41 54 | Decreasing | Previously dominant Omicron subvariant |
| MC.1 | 3 7 | Increasing | Descendant of KP.3.1.1 |
| Sources: 16 | |||
XEC Variant Symptoms and Differences
Current evidence indicates that the symptoms caused by the XEC variant are consistent with those seen in previous Omicron subvariants and typical COVID-19 presentations7 10. There are no confirmed reports of unique or new symptoms specifically associated with XEC7 10. The clinical picture remains dominated by respiratory and systemic symptoms that are common to COVID-19 infections.
- Congestion or runny nose11 12
- Cough and sore throat7 12
- Fatigue and muscle aches7 11
- Fever and chills7 11
- Headaches and dizziness13 11
- Loss of taste or smell (hyposmia) 1311
- Gastrointestinal symptoms such as diarrhea, nausea, and vomiting11
- Shortness of breath in some cases11
Severe disease manifestations, including acute respiratory distress syndrome (ARDS), encephalopathy, or cardiovascular complications, have not been reported as more frequent or severe with XEC compared to other Omicron subvariants13 . Most infections with XEC result in mild to moderate illness, similar to other circulating variants2 .
The similarity in symptomatology means that standard COVID-19 testing remains the primary diagnostic tool, as clinical presentation alone cannot distinguish XEC from other variants14 . Multiplex molecular testing is increasingly used to differentiate SARS-CoV-2 infections from other respiratory viruses that share overlapping symptoms14 .
The XEC variant, while more transmissible, does not currently cause more severe disease than previous Omicron subvariants, and vaccination remains the best defense against severe outcomes1 3.
The 2024025 updated COVID-19 vaccines, which include antigens from JN.1 and KP.2 lineages, are expected to provide effective protection against severe disease caused by XEC6 1. Although XEC exhibits some immune evasion capabilities due to mutations like Q493E, this does not appear to significantly reduce vaccine effectiveness against hospitalization and death1 .
Approved antiviral treatments such as Paxlovid, Veklury (remdesivir), and Lagevrio (molnupiravir) remain effective against recent Omicron subvariants, though specific clinical data on their efficacy against XEC are limited15 . Early initiation of antiviral therapy within the first few days of symptom onset is recommended to reduce the risk of severe illness11 .
- Receive the updated COVID-19 vaccine booster, especially before the winter season3 11
- Practice good hand hygiene and respiratory etiquette9
- Wear masks in crowded or indoor public spaces9
- Avoid close contact with individuals showing respiratory symptoms9
- Seek prompt testing and medical care if symptoms develop11
