US respiratory virus activity remains high, with flu B rising in 2 regions

sick schoolkid fever

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The nation's respiratory virus activity last week remained elevated, and flu levels rose in some regions of the country, partly due to a slight rise in influenza B activity, which is sometimes seen in the latter half of the flu season.

In its respiratory virus snapshot today, the Centers for Disease Control and Prevention (CDC) said COVID-19 indicators declined last week, with respiratory syncytial virus (RSV) levels continuing to decline in many areas.

Flu B fuels regional rises

The CDC said flu activity rose in the Central and Midwestern regions, mainly due to increasing detections of influenza B. And though flu test positivity remained stable nationally last week, it is increasing in the Middle Atlantic, Midwest, and Central parts of the country.

The percentage of outpatient visits for flulike illness remained steady, at 4.4%, and is still above the baselines for all 10 of the CDC's regions. Clinic visits for flu rose in young people ages 5 to 24 and remained stable for infants and toddlers, as well as for seniors.

Of viruses tested at public health labs, 76.1% were influenza A and 23.9% were influenza B. And of subtyped influenza A viruses, 67.5% were the 2009 H1N1 strain and 32.5% were H3N2.

Hospitalizations for flu decreased and were highest in seniors, followed by adults ages 50 to 64 and children ages 0 to 4.

Flu-related deaths trended downward overall, but the CDC reported 8 more pediatric flu deaths, raising the season's total to 74. The latest deaths occurred between the week ending December 23 and the week ending February 3. Seven were linked to influenza A, and, of 4 subtyped samples, 3 were H1N1 and the other was H3N2. One of the deaths was due to influenza B.

COVID markers show more declines

In its latest COVID-19 data update today, the CDC said its two main severity indicators—hospitalizations and deaths—both declined last week. Down 10% compared to the previous week, hospitalizations remain elevated in seniors and infants under 12 months of age. Deaths declined by 6.1%.

Early indicators also trended downward. Emergency department (ED) visits were down 10.8% and were highest in infants younger than 12 months and seniors. Test positivity declined by 0.6% and is at 10% nationally, with the level higher in parts of the Northeast and the South.

Wastewater levels nationally remain high but declining, according to CDC tracking. Biobot wastewater tracking shows an upward trend for the Northeast and level trends for other parts of the country.

Downward RSV trends, but hospitalizations elevated in seniors

RSV markers continue to decline in many areas. Hospitalizations are decreasing in young children but are still elevated in older adults, the CDC said.

ED visits and test positivity for RSV are also trending downward.

In its background information, the CDC said RSV activity typically occurs during late fall, winter, and early spring and that outbreak timing can vary by region and even among communities in the same region.

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