As new COVID strains spread in U.S., here's what we know

Multiple mutations of the omicron COVID-19 variant are making their way through the United States, but what do we know about these new strains?

Currently, the dominant strain in the U.S. is the EG.5 subvariant, which is responsible for nearly 21% of new cases in recent weeks, according to estimates from the Centers for Disease Control and Prevention.

Another omicron-spinoff, known as FL 1.5.1, is also increasing quickly, making up 13.3% of new cases, nearly double what it was responsible for a week ago.

Here is what we currently know about EG.5 and FL 1.5.1.

Both subvariants are descendants of XBB, with a mutation that is helping them spread more quickly than other variants, officials tell CBS News.

That development holds in line with previous versions of the virus, which typically mutate to find new ways around the immunity gained from vaccines or previous infections, according to CDC officials.

What are the symptoms?

Symptoms with EG.5 are nearly identical to previous omicron strains, according to the CDC.

Those symptoms typically mirror those of colds or the flu, and include cough, headache, muscle ache, runny nose, fatigue and fever. Loss of taste or smell can also occur, but isn’t as prevalent as earlier strains.

While most infections typically remain in the upper respiratory tract, they can also impact areas further into the body, especially in those with compromised immune systems. Those cases tend to be more serious and could require additional treatment.

Is there concern that they are causing more severe illness?

The WHO, which declared EG.5 a “variant of interest,” says that it has not observed any increase in illness severity with the new subvariant at this time.

Hospitalizations have begun to rise however, with more cases being reported across the U.S. as summer nears its end and as fall begins. That is also occurring in Illinois, where there has been "rising COVID activity" in recent weeks, according to the Illinois Department of Public Health.

Will new COVID vaccines work against these variants?

According to the CDC, vaccines still have some efficacy against the new strains, but a newer version of the formula will soon be rolled out across the U.S.

The new vaccine doses are expected to be available sometime in September, with the FDA meeting next month to give its approval of the new monovalent treatments.

According to studies conducted by Moderna, the new formulation is effective against the newer omicron subvariants, as it has been designed to target XBB 1.5, which followed the devastating BA.4 and BA.5 subvariants that ravaged the U.S. last year.