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Reports of respiratory illness have now reached "high" or "very high" levels across at least 16 state or big city health departments, the Centers for Disease Control and Prevention said, as trends of COVID-19 and influenza have accelerated in many parts of the country. And while a fast-growing new COVID variant called JN.1 is estimated to be driving a large share of the current winter wave of infections, officials say there have so far been no signs of new or unusual symptoms caused by the virus.

Here's the latest about what we know about this winter's wave so far.

Are COVID-19 symptoms still the same?

Experts caution that teasing out subtle changes to the symptoms being caused by different COVID-19 variants has proven tricky, given the now wide-ranging variety of antibodies that people have from either vaccinations, prior infections by different variants, or both.

"The types of symptoms and how severe they are usually depend more on a person's immunity and overall health rather than which variant causes the infection," the CDC said in a report on Dec. 8 discussing the JN.1 strain.

New survey data from the United Kingdom's health authorities, where COVID-19 and influenza trends are also on the rise, suggest common symptoms being reported from this winter's onslaught of respiratory infections, among all surveyed residents, include:

• Runny Nose (31.1%)
• Cough (22.9%)
• Headache (20.1%)
• Weakness or tiredness (19.6%)
• Muscle ache (15.8%)
• Sore throat (13.2%)
• Trouble sleeping (10.8%)
• Worry or anxiety (10.5%)

How those symptoms differ depending on whether people are specifically testing positive for COVID-19 versus other infections is not yet clear, though the U.K. Health Security Agency's Jonathon Mellor said Thursday that those more detailed analyses could come once their sample size grows.

Research through last winter, co-authored by health authorities in the U.K., found symptoms were similar for COVID-19 and other germs that often drive respiratory illnesses during the winter.

"Cough, sore throat, sneezing, fatigue and headache were all among the most commonly reported symptoms for each of the three infections, suggesting that discriminating between SARS-CoV-2, influenza and RSV based on symptoms alone may prove challenging," they wrote in a preprint, that has not been peer-reviewed, released in October.

That is also in line with other research from previous waves of COVID-19.

Research through 2022 from the CDC's nationwide household transmission study, released as a preprint in May, which has also not yet been peer-reviewed, found commonly reported symptoms among household contacts infected by the BA.5 variant were:

• Any symptom (77%)
• Cough (63%)
• Fever (48%) 
• Shortness of breath (22%)
• Change of taste or smell (20%)

Prevalence of most COVID symptoms were not far off from those reported before even the Delta variant emerged in late 2020.

The exception to this is reports of change in taste or smell, which declined from 42% early in the pandemic. Unlike many other COVID-19 symptoms, researchers around the world have confirmed a steep decline in reports of loss of taste or smell — a symptom that was much more common when COVID first swept the globe.

Faster incubation period?

Other subtle changes that scientists have tracked to the virus is a gradual decline in the "incubation period," or length of time that it takes for people to get sick after being exposed to COVID-19. 

Research published by the CDC from authors in Japan and Singapore earlier this year found this time may have shortened to as little as 2 to 3 days on average.

Long COVID rates and symptoms

Data suggests long COVID rates may have declined since the beginning of the pandemic. Exact definitions vary, but the CDC generally considers long or "post-COVID" conditions to be symptoms that persist or emerge at least four weeks after otherwise recovering from the virus.

"Approximately 1 in 10 adults with previous COVID-19 were experiencing long COVID at the end of the study period, highlighting the ongoing importance of COVID-19 prevention actions, including vaccination," a CDC study of Census Bureau survey data said in August, noting that its prevalence among people who said they previously caught COVID-19 had not changed since January 2023.

In a separate CDC analysis of the same ongoing survey, 4.6% of American adults in October reported having limitations on their activities from long-term symptoms of the virus, down from 5.7% at the same time in 2022.

Another study, published in the medical journal JAMA in May, identified 12 symptoms most commonly associated with long COVID:

• post-exertional malaise (debilitating fatigue that gets worse after physical or mental activity)
• fatigue
• brain fog
• dizziness
• gastrointestinal symptoms
• heart palpitations
• issues with sexual desire or capacity
• loss of smell or taste
• thirst
• chronic cough
• chest pain
• abnormal movements

Other symptoms were reported by smaller numbers of patients, with the study noting 37 symptoms that were more common in those who'd had a COVID infection, after 6 months, than in people who hadn't been infected.

Have COVID-19 testing recommendations changed?

Guidance from U.S. authorities on testing and treatment remain largely unchanged for this winter.

For most COVID-19 home tests, like the free rapid antigen kits that all American households can request from the Biden administration this winter, the FDA's guidance remains unchanged since last winter.

• More free COVID-19 tests can be ordered now. Here's how.

If you at first get a negative result from the antigen test, but have symptoms or think you were exposed to the virus, the FDA says you should swab your nose "again 48 hours after." 

That was the result of studies the FDA and National Institutes of Health backed earlier during the pandemic which found the likelihood of false negative results from antigen tests was reduced after repeated testing.

These recommendations only apply to antigen tests, which the CDC says "are generally less sensitive" to picking up infections.

Home molecular tests for COVID-19, like the Lucira kit from Pfizer that in February was first greenlighted by the FDA to test for influenza as well, have yielded more accurate results.  Among positive COVID-19 samples, 88.3% were correctly spotted in studies of the test.

Another method some have floated to try to improve the accuracy of COVID testing has been to swab inside the throat or mouth as well, similar to what is done for some tests in many countries overseas. So far, that approach hasn't been authorized by the FDA for use in home tests, in part over safety concerns, though the agency now says it is "open" to considering it.

"Although there are not currently any COVID-19 tests authorized by the FDA for self-collection of throat swabs, the FDA is open to reviewing tests with novel sample types," James McKinney, an FDA spokesperson, told CBS News in a statement.

A study published this month from Denmark found combining self-collected nose and throat swabs upped the sensitivity of testing by 15.5 percentage points.

"As with all devices, the FDA would evaluate them for both safety and effectiveness, including considering any possible safety concerns regarding self-collection of throat swabs.  Self-collection of throat swabs is more complicated than nasal swabs — and if done incorrectly, can potentially cause harm to the patient," said McKinney.

In:
• COVID-19
• COVID-19 Pandemic

Alexander Tin

Alexander Tin is a digital reporter for CBS News based in the Washington, D.C. bureau. He covers the Biden administration's public health agencies, including the federal response to infectious disease outbreaks like COVID-19.

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