The latest dominant COVID strain in the United States is XFG.1.1, which accounts for about 32% of circulating virus as of early April 2026. Together with its parent lineage XFG (13%) and the closely related XFG.14.1 (8%), the XFG family now makes up over half of all sequenced cases in the country.
What the XFG Lineage Is
XFG and its sublineages are descendants of the JN.1 family of Omicron variants that became dominant in late 2023 and early 2024. Like previous waves, these newer strains carry mutations in the spike protein that help them sidestep some of the immunity people built up from earlier infections and vaccinations. That immune evasion is the main reason one lineage replaces another: it spreads more efficiently in a population that already has partial protection.
This follows a pattern that has played out repeatedly since Omicron first appeared. The XEC variant, for instance, rose to prominence earlier as a hybrid of two JN.1-related variants and represented 14 to 22% of circulating virus during its peak before being overtaken by XFG. Each new subvariant tends to have a modest growth advantage over the last, which is enough to shift the balance over a period of weeks.
Symptoms of Current Strains
There is no evidence that XFG causes a meaningfully different set of symptoms compared to other recent Omicron subvariants. The CDC notes that symptoms can vary with new variants and with a person’s vaccination status, but the overall profile has remained consistent for the Omicron era. Common symptoms include:
- Fever or chills
- Cough and sore throat
- Congestion or runny nose
- Fatigue and muscle aches
- Headache
- Shortness of breath
- Loss of taste or smell (less common than with earlier variants)
- Nausea, vomiting, or diarrhea
For most people with some level of immunity from prior infection or vaccination, these symptoms resemble a bad cold or mild flu and resolve within a week. Severe illness remains concentrated among older adults, people with weakened immune systems, and those with chronic conditions like heart disease, diabetes, or lung disease.
Incubation and Contagious Period
Omicron-era variants generally have a shorter incubation period than the original virus. Early in the pandemic, the average gap between exposure and symptoms was about 6.5 days. With Delta, that dropped to roughly 4.3 days. With Omicron and its descendants, the median incubation period sits at 3 to 4 days, meaning you’ll typically know within a few days of exposure whether you’re infected.
You’re most contagious from just before your symptoms start through the first few days of illness. Most people can shed virus for up to 10 days after infection, though the amount of virus drops significantly after the first several days. If you test positive, staying away from others during the first five days of symptoms and wearing a mask around people for a few days after that remains practical guidance for limiting spread.
Do Treatments Still Work?
The main antiviral prescribed for COVID (sold as Paxlovid) has continued to work against newer Omicron subvariants. A large retrospective study in South Korea found that patients treated with this antiviral had roughly 72% lower odds of progressing to severe or critical illness, and about 63% lower odds of dying, compared to untreated patients. These numbers held steady even as the dominant variant shifted from one Omicron sublineage to another.
This is reassuring because Paxlovid targets a part of the virus’s replication machinery that doesn’t mutate as quickly as the spike protein. That means the drug’s effectiveness is less likely to erode with each new variant wave. It’s most effective when started within the first five days of symptoms, so getting tested early matters if you’re in a higher-risk group.
What This Means for Vaccines
COVID vaccines are updated periodically to better match circulating strains, similar to the annual flu shot. Because XFG descends from the JN.1 lineage, vaccines formulated to target JN.1 or its close relatives provide the closest match currently available. Immunity from any recent vaccination still reduces your risk of severe illness even when the match isn’t perfect, because your immune system recognizes enough of the virus to mount a faster response.
If your last COVID vaccine was more than a year ago, your protection against infection has likely waned, though protection against hospitalization tends to last longer. People over 65 and those with compromised immune systems benefit the most from staying up to date.