US respiratory virus infections rise, led by flu

During Christmas week, respiratory virus activity continued a steady rise across much of the nation, with the largest spikes seen for flu. COVID-19 levels continue to climb from low levels, and respiratory syncytial virus (RSV) activity is still very high in many regions, the Centers for Disease Control and Prevention (CDC) said today in its latest updates.

Emergency department (ED) visits for flu and RSV are very high, with the steepest rise for flu. For COVID, ED visits are highest among young children and older adults. 

Flu hospitalizations up in all age-groups

Meanwhile, flu hospitalizations continue a steep rise compared to the other two viruses, coming in at 7.8 per 100,000 hospitalized people, roughly twice the level as for COVID, according to data from the CDC’s National Healthcare Safety Network. 

Flu hospitalizations are on the rise for all age-groups but are highest in seniors. COVID hospitalizations, tracking higher from a low level, remain highest for older people, with RSV hospitalizations rates highest in young children and older adults.

The weekly percentage of deaths, however, is higher for COVID than for flu or RSV, according to the latest CDC data.

Flu is also leading the other two viruses for test positivity, rising from 12.0% to 18.7% compared to the previous week. For comparison, COVID test positivity has risen to 7.0%, with the level for RSV at 12.7%.

The percentage of outpatient visits for flulike illness also saw a jump last week, up from 4.9% to 6.8%. Flu is at the high or very high level across 42 states, with the highest levels across the South, Southwest, and part of the Northwest, including Idaho and Oregon.

Among other flu metrics, the CDC said nearly all of the detections are influenza A, and, of subtyped samples at public health labs, 59.3% were H3N2 and 40.7% were the 2009 H1N1 virus. The agency received reports of 2 more pediatric flu deaths, which push the total reported this season to 11.

Wastewater tracking shows Midwest as COVID hot spot

Nationally, COVID levels remain at the high level, though detections in the Midwest are nearly twice that of the national level. Levels are showing rising trends, however, in other US regions.

For comparison, wastewater levels are moderate for both flu and RSV.

In its weekly respiratory virus snapshot, the CDC said it still expects hospitalizations from the respiratory viruses over the fall and winter to have a similar or lower peak than last season, though officials expect the overall peak hospitalization to remain higher than before SARS-CoV-2 emerged.