US flu markers show hint of a second wind


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After declining trends over the past few weeks, flu activity rose in some parts of the country, while COVID-19 and respiratory syncytial virus (RSV) levels continued overall declines, according to the latest updates today from the US Centers for Disease Control and Prevention (CDC).

Though flu indicators declined following the winter holidays, the CDC has said that it is watching for a second peak that sometimes occurs after the winter holidays. In its respiratory virus snapshot, the CDC said some regions are seeing rising flu indicators, especially in the Midwest and South-Central regions.

Signs of a flu comeback?

Also, the percentage of respiratory samples that were positive for flu at clinical labs rose last week to 16.2%, compared to 14.2% the previous week, the CDC said in its weekly flu update. Influenza A is still dominant, with 60.4% of subtyped samples belonging to the 2009 H1N1 subtype. There were increases in the percentages of H3N2 and influenza B detections compared to the previous week.

Outpatient visits for flulike illness held steady and have been above the national baseline since November. However, CDC surveillance shows a rise for one age-group: people ages 5 to 24 years.

Eight more pediatric flu deaths were reported, lifting the season's total to 65. The deaths all occurred in January. Four were linked to influenza A, and four involved influenza B. Overall deaths from flu declined slightly compared to the week before.

COVID wastewater levels decline further

Most COVID markers declined last week, except for deaths, which held steady. Hospitalizations for COVID, one of the CDC's main severity indicators, decreased by 10.9% compared to the previous week.

Among early indicators, test positivity declined 4.6% and it at 6.3% nationally. However, levels were a bit higher in the Midwest, South, and parts of the Northeast. Emergency department visits dropped 11% compared to the previous week and remain highest for infants and seniors.

The CDC's wastewater tracking shows that virus detection levels are high, down from "very high" the week before. Meanwhile, Biobot wastewater tracking shows that a steady decline in SARS-CoV-2 detections since late December has slowed, with the western region showing a slight increase.

In its every-other-week variant projections, the CDC said JN.1 continued to expand its dominance and now makes up 93.1% of sequenced samples, up from 84.3% in its last update.

Scientists eye new SARS-CoV-2 variant

Earlier this week, South African virus sequencing experts identified a new lineage from samples in South Africa that has more than 100 mutations. Tulio de Oliveira, PhD, who directs South Africa's Centre for Epidemic Response and Innovation and is also deputy director of the Wellcome Sanger Institute Genomic Surveillance Unit, said on X (formerly Twitter) that the lineage is the most divergent one identified this year.

The same group in South Africa was the first to identify the Omicron SARS-CoV-2 variant.

Scientists have designated the new variant as BA.2.87.

The lineage has been found in eight samples from two different provinces between September and November. It is distinct from currently circulating Omicron lineages and shows some diversity in the samples collected over a 10-week period.

De Oliveira said enhanced genetic surveillance shows very few signs that the new variant is spreading widely or replacing current lineages. He added that work is under way to assess potential transmissibility and pathogenicity.

RSV hospitalizations decline in young kids

The CDC said RSV activity has declined across many parts of the nation. Hospitalizations, still elevated, are declining in young children, but they remain elevated in older adults.

In its vaccination updates, the CDC estimated that 20.8% of eligible adults ages 60 and older have received an RSV vaccine.

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