New COVID variant ‘Stratus’ is spreading in the U.S. and worldwide

A new COVID variant is climbing the ranks in the U.S., becoming the third-most common strain of the summer.

Variant XFG, colloquially known as "Stratus," was first detected in Southeast Asia in January but accounted for less than about 0% of cases in the United States until May. By late June, it was estimated to account for up to 14%, according to the Centers for Disease Control and Prevention (CDC).

The World Health Organization (WHO) added XFG to its watchlist but evaluated the additional public health risk posed by the variant as "low" at the global level in a late June report, in which it also advised that currently approved COVID-19 vaccines are "expected to remain effective to this variant against symptomatic and severe disease."

Here's what we know about XFG.

What is COVID variant XFG?

XFG is a combination of COVID-19 variants F.7 and LP.8.1.2, the latter of which is currently the second most prominent strain in the U.S.

The variant's mutations may enhance XFG's ability to evade immune responses, but its binding behavior shows that it is less likely to be highly contagious than other dominant variants, Subhash Verma, microbiology and immunology professor at the University of Nevada, Reno, told USA TODAY.

"There is currently no clear evidence that XFG causes more severe disease or significantly different symptoms than earlier Omicron variants," said Verma. "Importantly, there are no immediate public health concerns associated with this variant."

How common is XFG?

While XFG has been growing and spreading worldwide, it has yet to become the predominant source of infection in the United States.

The CDC has moved to using longer timeframes for COVID tracking due to low reporting from states. According to the latest data for the two-week period ending June 21, XFG accounted for 14% of U.S. cases, making it the third most-prevalent strain after NB.1.8.1 (43%) and LP.8.1 (31%).

The prominence of XFG in the United States significantly increased in the weeks leading up to the last report, accounting for 0% of cases through March before reaching 2% in April, 6% in late May, 11% in early June and 14% in late June.

WHO tracked an uptick in XFG worldwide in June as well, with the June report including data from 38 countries showing that XFG accounted for only 7.4% of positive tests in the first week of May but 22.7% by the last.

USA TODAY has reached out to the CDC for more information about the spread of COVID variants in July and August.

What are the symptoms of XFG?

There is no evidence that XFG causes any distinct symptoms from other variants, said Verma. However, hoarseness has been anecdotally associated with the strain, according to social media posts and news reports.

The CDC outlines the following as common COVID-19 symptoms:

The CDC advises seeking medical care if you experience any of the following symptoms:

This article originally appeared on USA TODAY