Flu activity peaked with no spike in cases after holiday, but respiratory virus season still in full swing


The flu continues to be widespread in the United States, but the first wave of the season – which swept the country weeks earlier than usual – appears to have peaked.

The weeks following the holiday season brought sustained high levels of transmission and hospitalizations, but influenza activity does not appear to have increased as many public health experts have warned.

Yet even after weeks of improvement, data released Friday by the US Centers for Disease Control and Prevention shows more than 12,400 people were admitted to hospital with flu in the first week of the new year, and nearly 9% of lab tests were positive for influenza.

About 4% of all people who saw a health care provider in the past week had symptoms of respiratory viruses, including fever and a cough or sore throat, which is almost twice as high as the national reference level.

The flu is notoriously unpredictable and one season can bring several peaks of activity.

“It’s pretty clear there’s been a spike in activity, but that doesn’t mean we won’t have another one,” Lynnette Brammer, head of the national surveillance team, said last week. flu from the CDC. “Things could turn around and go back up.”

Flu vaccination rates remain well below ideal levels and hospitals remain very full, leaving the United States vulnerable as the respiratory virus season drags on.

“It’s definitely something that we’re going to be watching very carefully. We’re just going to have to keep an eye on all the data, see what viruses are circulating and who’s getting sick, and what kind of impact that is having,” Brammer said.

“And I want to remind people that if they haven’t gotten the shot yet, get it. It is not too late.”

As of December 31, about 171 million doses of flu vaccine had been distributed in the United States — enough to cover only about half the population. According to CDC data, only 40% of adults had been vaccinated by the end of November and only 48% of children had been vaccinated by the end of December.

Through Jan. 7, the CDC estimates there have been 24 million illnesses, 260,000 hospitalizations and 16,000 deaths from the flu this season.

Although this season has hit earlier than usual, the results are within an expected range – at least so far.

“This is not an exceptionally high flu season. It’s kind of in the middle to upper range, but it’s within what we normally expect to see during a regular flu season, unfortunately,” Brammer said. “So basically it looks like a typical flu season, except in terms of timing. It was just a little earlier than usual. »

Overall, influenza and other respiratory virus activity remains “high” or “very high” in about half of the states, according to new CDC data, and the United States continues to face multiple respiratory viruses circulating at high levels.

RSV activity also peaked in the United States, reaching a seasonal high in mid-November. But even after a sharp decline in trends over the past month and a half, weekly hospitalization rates for RSV remain above the peaks of more recent seasons.

RSV is particularly dangerous for children, and at least 13 out of every 100,000 children under 5 were hospitalized with RSV in the last week of the year, bringing the cumulative hospitalization rate this season to 5 out of 1,000 children in this age group. .

Meanwhile, Covid-19 activity has been on the rise for a few months.

Hospitalizations have been on the rise since November and surpassed the most recent peak this summer, before the updated recall became available, according to federal data.

Case reporting has become more erratic during the pandemic, but sewage monitoring data from Biobot Analytics suggests Covid-19 activity is also higher than it was during the outbreak. delta.

The fast-growing Omicron subvariant XBB.1.5 now accounts for about 43% of new Covid-19 cases in the United States, according to the CDC, making it the strain causing the most new infections in the United States. United.

It is notably the only variant that is gaining ground in the United States.

XBB.1.5 was first detected in New York in October. It has grown rapidly throughout the Northeast, and the CDC estimates it accounts for more than 80% of new cases in that region.

From there, XBB.1.5 seems to be gaining momentum along the East Coast. It now accounts for about half of Covid-19 cases in mid-Atlantic states and nearly a third of cases in the Southeast. It is less common in other parts of the United States.

The rise of XBB.1.5 coincided with an increase in hospitalizations linked to Covid-19, especially among seniors.

XBB.1.5 has a key mutation that helps it bind more tightly to cells. Experts believe this could help him be more contagious.

Yet only 16% of the US population received their updated Covid-19 booster shot. Data from October shows that people aged 5 and over who received an updated booster had a 19 times lower risk of dying from Covid-19 compared to those who were not vaccinated. The odds of testing positive were three times lower for those who had their recall updated.

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