EG.5 subvariant now the dominant COVID-19 strain in the US, picture remains unclear

The COVID-19 omicron subvariant EG.5 is now the most dominant strain in the U.S. according to the latest genomic surveillance data from the Centers for Disease Control and Prevention (CDC), but lax data collection makes it hard to tell what this means for the country.

The EG.5 omicron subvariant accounts for 17.3 percent of coronavirus infections in the U.S., according to the CDC data, having jumped by 5 percent in the two weeks when the proportions were last updated.

The prevalence of EG.5 is relatively minor at the moment, with the second most prevalent strain XBB.1.16 accounting for 15.6 percent of cases.

The CDC no longer tracks national COVID-19 case rates, though hospitalization data is still updated regularly. Hospitalizations due to SARS-CoV-2 have risen slightly in the past few weeks suggesting higher levels of transmission, but it remains uncertain if this trend can be attributed to EG.5’s recent growth.

With the end of the national public health emergency for COVID-19 earlier this year, viral data collection has become far less comprehensive. The CDC currently only has genomic data from three of the 10 U.S. regions under the Department of Health and Human Services (HHS).

EG.5 is only dominant in one of three HHS regions where genomic data is available: Region 4, which encompasses much of the Southeast.

EG.5 falls within the XBB family of omicron subvariants, mutating from the XBB.1.9.2 strain. The subvariant XBB.1.5 held dominance in the U.S. for several months straight before being briefly overtaken by XBB.1.16 in July.

According to the World Health Organization (WHO), EG.5 was first detected in February of this year. Last month, the WHO classified EG.5 as a “variant under monitoring,” meaning it has genetic differences that may indicate “early signals of growth advantage” compared to other circulating strains, but more assessment of the variant is needed.

This current designation separates EG.5 from variants of concern, which the WHO considers to have a “substantial impact” on the ability of health care systems to care for patients with COVID-19, as well as variants of interest that are associated with a growing number of cases or other epidemiological risks.

The dominant strain’s relative genetic closeness to XBB.1.5 may serve as a boon for the U.S. as it heads into the fall. Health authorities are preparing for a fall COVID-19 vaccine campaign and vaccine manufacturers are developing their updated shots to target XBB.1.5, as it was the most dominant strain by far when health advisory committees chose the strain for this upcoming season.

While XBB.1.5 may not be the most widely circulating strain of COVID-19 this fall, health officials are anticipating that the most prevalent strain will be close enough that the vaccine offers strong enough cross-protection against severe disease and hospitalization.

For the latest news, weather, sports, and streaming video, head to The Hill.