As the festive season kicks into high gear, health authorities in the United States are sounding the alarm over a simultaneous rise in COVID-19 and influenza cases. The convergence of colder weather, increased indoor gatherings, and one of the busiest travel periods of the year is creating ideal conditions for respiratory viruses to spread, potentially leading to a significant surge in infections in the coming weeks.
Stratus Variant Drives Gradual Uptick Nationwide
After a late-summer wave driven by the highly contagious XFG variant, commonly known as "Stratus," the US saw a relative slowdown in COVID-19 activity during the fall. However, that trend is now reversing. According to the latest data from the Centers for Disease Control and Prevention (CDC), as of December 16, COVID-19 infections were growing or likely growing in 31 states, were stable in 15 states, and were declining in just one state.
The Stratus subvariant continues to dominate cases across the country. Similar to other Omicron descendants, it transmits easily, particularly in crowded indoor settings—a scenario that will become increasingly common with holiday parties and family reunions. This risk is amplified by relatively low uptake of the updated COVID-19 vaccine.
Wastewater Data and Hospitalizations Paint a Concerning Picture
While overall national COVID-19 levels remain below the peaks of previous winter surges, multiple surveillance systems indicate a clear upward trend. For the week ending December 13, the CDC's national wastewater surveillance classified viral activity as "low." Despite this, 15 states reported "high" or "moderate" activity levels, with a notable concentration in the Midwest.
Another monitoring program, WastewaterSCAN—run by Stanford and Emory Universities—presents a broader view, showing SARS-CoV-2 concentrations in the "high" range across the nation. A spokesperson for the program confirmed to TODAY.com that these concentrations have risen by 21% since November.
"Clearly, influenza has taken a big jump up this last week ... but COVID has been moving up in a more gradual way," noted Dr. William Schaffner, a professor of infectious diseases at Vanderbilt University Medical Center. He added that hospitalizations linked to COVID-19 are also beginning to edge upward, especially among adults aged 65 and older.
Regional Hotspots and the Seasonal Pattern
The current increases are most pronounced in the Midwest and Northeast regions of the United States. Based on CDC wastewater data from December 18, the following states are reporting "high" or "moderate" levels of COVID-19 viral activity:
- Arizona
- Connecticut
- Kansas
- Kentucky
- Maine
- Massachusetts
- Michigan
- Minnesota
- Nebraska
- New Hampshire
- New Mexico
- Ohio
- Oklahoma
- South Dakota
- West Virginia
Dr. Schaffner pointed out that while the rising numbers are concerning, they follow a familiar seasonal pattern. COVID-19 can cause surges year-round but typically produces two major waves: one in the winter and another in late summer. These spikes are influenced by a combination of new variants, waning immunity from prior infections or vaccinations, and increased travel and social mixing indoors.
As millions prepare for holiday celebrations, health experts emphasize the importance of preventive measures—including vaccination, good ventilation, and staying home when sick—to curb the spread during this vulnerable period.
