Omicron Vs. Delta Symptoms: How New COVID Strain Might Differ From Previous Cases

Health experts are still investigating, but here's what we know so far

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While scientists and experts are still working to find answers to many unanswered questions surrounding the new omicron COVID variant, some doctors in South Africa who have treated cases said the symptoms appear to differ from what many have come to expect with the delta variant.

As the emergence of the new COVID variant omicron begins to restrict U.S. travel and raises global concerns due to its increased risk of reinfection, scientists and doctors are working to collect data around how and why this variant behaves differently than others.



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Three top Boston doctors explain what the new omicron variant is, whether it's already in the U.S., what the symptoms are and if vaccines protect against it on the weekly “COVID Q&A” series.

So what are the symptoms of the new omicron COVID variant and the delta COVID variant?

Though health experts have said it will take weeks to understand how the variant may affect diagnostics, therapeutics and vaccines, here's what we know so far.

Omicron COVID variant symptoms

COVID symptoms linked to the omicron variant have been described as "extremely mild" by doctors in South Africa who first raised the alarm over the new strain.

Most of the new cases in South Africa have been among people in their 20s and 30s, and doctors note that age group generally has milder symptoms of COVID-19 in any case.

They warn though that older people infected by the new variant could have more severe symptoms.

“We've seen a sharp increase in cases for the past 10 days. So far they have mostly been very mild cases, with patients having flu-like symptoms: dry coughs, fever, night sweats, a lot of body pains," said Dr. Unben Pillay, a general practitioner in Gauteng province where 81% of the new cases have been reported.

Dr. Angelique Coetzee, chair of the South African Medical Association, told the BBC on Sunday that she started to see patients around Nov.18 presenting with "unusual symptoms" that differed slightly to those associated with the delta variant, which is the most virulent strain of the virus to date and globally dominant.

"It actually started with a male patient who's around the age of 33 ... and he said to me that he's just [been] extremely tired for the past few days and he's got these body aches and pains with a bit of a headache," she told the BBC.

The patient didn't have a sore throat, she said, but more of a "scratchy throat" but no cough or loss of taste or smell — symptoms that have been associated with previous strains of the coronavirus.

Coetzee said she tested the male patient for COVID, and he was positive, as was his family, and then said she saw more patients that day presenting with the same kinds of symptoms that differed from the delta variant.

Other patients she had seen so far with the omicron variant had also experienced what she described as "extremely mild" symptoms, and she added that her colleagues had noted similar cases.

"What we are seeing clinically in South Africa — and remember I'm at the epicenter of this where I'm practicing — is extremely mild, for us [these are] mild cases. We haven't admitted anyone, I've spoken to other colleagues of mine and they give the same picture."

Delta COVID variant symptoms

Symptoms of the delta COVID variant are similar to that of the alpha COVID strain (B.1.1.7), but are found to cause more cold-like symptoms.

"Headache, sore throat, runny nose, and fever are present based on the most recent surveys in the U.K., where more than 90% of the cases are due to the delta strain," Dr. Inci Yildirim, a Yale Medicine pediatric infectious diseases specialist said when the strain was first detected earlier this year.

According to scientists at Yale Medicine, the delta variant is 50% more contagious than the alpha COVID variant, meaning the number of people that could potentially be infected by each COVID-positive individual is significantly higher. 

Experts said it remains unclear how the omicron variant compares in terms of its ability to spread.

Alpha COVID variant symptoms

The most commonly reported symptoms from B.1.1.7, the first COVID variant originally detected in the United Kingdom, include fatigue, headache, sore throat, fever or loss of taste and smell, according to Johns Hopkins Medicine.

But COVID can show up in a myriad of forms depending on the person, and symptoms like fever, fatigue and breathing problems have been reported to linger on and off for days and weeks —often referred to as 'long COVID' — following the initial onset of the virus, according to experts.

What's the full list of COVID-19 symptoms, according to the CDC?

Without getting tested, medical experts say it will be nearly impossible to tell the difference between the omicron COVID variant from the beginning of influenza or even most common colds in the winter.

Overall, according to the Centers for Disease Control and Prevention, people with COVID-19 have reported a wide range of symptoms, from mild to severe.

Symptoms may appear two to 14 days after exposure to the virus and can include:

  • Fever or chills
  • Cough
  • Shortness of breath or difficulty breathing
  • Fatigue
  • Muscle or body aches
  • Headache
  • New loss of taste or smell
  • Sore throat
  • Congestion or runny nose
  • Nausea or vomiting
  • Diarrhea

If the omicron COVID variant has mild symptoms, why is it a 'variant of concern'?

WHO Health Emergencies Programme COVID-19 Technical Lead Dr. Maria Van Kerkhove said early evidence on omicron shows that the variant has a large number of mutations, some of which have concerning characteristics -- including an increased risk of reinfection compared to other highly transmissible variants.

That means people who contracted COVID and recovered could be more subject to catching it again with this variant.

Variants are categorized into three categories: (1) "variants of interest," (2) "variants of concern" and (3) "variants of high consequence."

A variant of concern is one in which "there is evidence of an increase in transmissibility, more severe disease (e.g., increased hospitalizations or deaths), significant reduction in neutralization by antibodies generated during previous infection or vaccination, reduced effectiveness of treatments or vaccines, or diagnostic detection failures," according to the CDC.

How effective are vaccines against each COVID variant?

Studies have shown that the COVID-19 vaccines are effective against both the alpha variant and the delta variant.

However, scientists don't know yet how effective vaccines are against the new omicron COVID variant, which has been detected in North America but not yet in the United States.

Moderna's Chief Medical Officer Paul Burton said Sunday the vaccine maker could roll out a reformulated vaccine against the omicron coronavirus variant early next year.

The vaccine maker "mobilized hundreds" of workers starting early Thursday morning, on Thanksgiving, to start studying the new variant, the company said in a statement

It's not clear whether new formulations will be needed, or if current COVID vaccinations will provide protection against the new variant that has begun to spread around the globe.

"We should know about the ability of the current vaccine to provide protection in the next couple of weeks, but the remarkable thing about the mRNA vaccines, Moderna platform is that we can move very fast," Burton said on BBC's "Andrew Marr Show."

"If we have to make a brand new vaccine I think that's going to be early 2022 before that's really going to be available in large quantities," the Moderna chief added.

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