The latest COVID-19 variant known as XFG, nicknamed Stratus, continues to spread throughout the United States, driving a summer spike in cases. Stratus accounted for an estimated 79% of COVID cases in the U.S. during the week ending September 6, far surpassing the NB.1.8.1 Nimbus variant, according to the latest data from the U.S. Centers for Disease Control and Prevention. 

“Stratus has been around in Southeast Asia since January of this year, and came to the United States around the spring,” explains Dr. Magdalena Sobieszczyk, chief of the Division of Infectious Diseases at NewYork-Presbyterian/Columbia University Irving Medical Center. “We’ve been seeing an uptick since July, predominantly because it’s a variant that can be transmitted easily and people were travelling a lot more, vaccine uptake has not been very high, and now many people are returning to school and their regular routines.”

The good news is that simple measures (like vaccination, washing hands and wearing a mask) can help protect yourself and others from COVID this fall.

“Typically, respiratory viruses peak in the winter, but with coronavirus we’re also seeing it in the warm weather months,” says Dr. Sobieszczyk. “I think we will see more cases, but I don’t expect a surge in hospitalizations. We have many ways to prevent it and protect ourselves, we just have to use them.”

Health Matters spoke with Dr. Sobieszczyk on what to know about XFG, the latest on COVID vaccines, and how to stay safe this upcoming respiratory virus season.

Is the new COVID variant Stratus more transmissible? 

XFG, or Stratus, comes from the Omicron family and is a hybrid of two existing Omicron subvariants, LF.7 and LP 8.1.2. Its mixture of genetic information helps it bind a little bit tighter to the cells in the body and cause infection that may make it more transmissible.

Like the other variants, it has unique mutations which improve its ability to evade COVID-19 antibodies from prior infection or from prior vaccination.  

What are the symptoms of Stratus? Are they similar or different from other COVID variants?

A sore throat seems to be the predominant symptom, but overall, Stratus symptoms are not any different than those of other COVID variants.

People may experience:

• Fever
• Fatigue
• Cough
• Sneezing
• Runny nose or congestion
• Nausea, vomiting or diarrhea.

So far, XFG has not caused severe disease when compared to other variants and we have not seen a dramatic increase in hospitalization, which is reassuring.

Will the COVID vaccine protect against XFG Stratus?

The currently available COVID-19 vaccine updated for the 2025-2026 season targets a strain called LP.8.1, which is closely related to the predominant strain. We expect that the vaccine should be effective at protecting against severe disease, and there are no new concerns about safety or efficacy.

Talk to your clinician about getting the latest vaccine.

An important point about these vaccines for respiratory infections is that they won’t always prevent someone from getting the sniffles or mild COVID, but they still protect from severe illness, especially for people who are vulnerable.  We are all healthier when everyone is vaccinated and thanks to vaccines, we develop and maintain community and household immunity. Vaccines protect not only the individual but also people around them.

What are additional ways people can protect themselves from COVID, especially during the upcoming respiratory virus season?

It is important to keep in mind that respiratory illnesses like COVID, RSV, and the flu can have a lingering effect on health. COVID in particular — even after an asymptomatic or mild infection — can, in some people, lead to lingering symptoms called long COVID, which vaccination may also help prevent. I recommend people speak with their clinicians about more tailored ways to protect themselves, especially if they or their loved ones have underlying conditions, such as diabetes, heart disease or high blood pressure.

Vaccines are one of our key strategies for preventing transmission and reducing severe outcomes of infection. Other than getting vaccinated, it’s amazing how such a simple thing like handwashing can be so powerful. Testing for COVID or other respiratory illnesses is important if you have symptoms because you can reduce the risk of transmitting infection. If you’re sick, social distancing does help. Lastly, wearing a mask if you’re feeling sick or vulnerable to infection can help protect you and others. If you’re recovering from COVID, an N95 is more effective, but in general, masks can help stop the spread.

Magdalena Sobieszczyk, M.D., is the chief of the Division of Infectious Diseases at NewYork-Presbyterian/Columbia University Irving Medical Center and is the Harold Neu professor of infectious diseases in medicine at Columbia University Vagelos College of Physicians and Surgeons. Dr. Sobieszczyk is also a clinical virologist and the principal investigator of the Columbia Collaborative Clinical Trials Unit, funded by the National Institutes of Health, which has been advancing the science of infections like SARS-CoV-2 and HIV.