Preliminary research and anecdotal evidence from physicians suggest the omicron variant may cause slightly different symptoms than previous coronavirus strains. However, experts say it's still too early to make any definitive statements, according to The New York Times.
Here's what early research shows:
1. A Dec. 17 CDC analysis of the first 43 omicron cases investigated in the U.S. found the four most common symptoms were cough, fatigue, congestion and runny nose. The CDC noted characteristics of the cases described in its analysis may not be generalizable, as the findings might be associated with individual characteristics.
2. A separate CDC report published Dec. 31 analyzed an early cluster of omicron cases in Nebraska. Six members of the same household tested positive for COVID-19 Dec. 1 shortly after one family member — a 48-year-old unvaccinated man — returned from a trip to Nigeria. Of the man's five household contacts who tested positive, four were unvaccinated.
The man and four other household members all had previously confirmed COVID-19 infections. These individuals said their COVID-19 symptoms and illness severity from the omicron variant were similar or milder than their previous infections. The fifth unvaccinated family member who had not previously had COVID-19 experienced cough, joint pain, congestion, fever and chills.
"It is unknown whether the mild clinical syndromes or differing symptom descriptions are a result of existing immunity or altered clinical features associated with omicron infection," CDC said.
3. In mid-December, Discovery Health — South Africa's largest health insurer — released preliminary real-world data on 211,000 COVID-19 cases, 78,000 of which involved the omicron variant. The data showed the most common symptoms among omicron patients were a scratchy or sore throat, nasal congestion, a dry cough and muscle pain, especially in the low back area. The data only covers the first three weeks of the country's omicron outbreak and could change as the wave continues, researchers said.
4. Preliminary research suggests loss of sense of taste and smell may be less common with omicron. A December analysis of a small omicron outbreak among 111 vaccinated people in Norway found just 23 percent of people lost their sense of taste, and 12 percent lost their sense of smell. In contrast, a systematic review published in 2020 suggests that 48 percent of people infected with the original SARS-CoV-2 strain reported loss of smell and 41 percent experienced loss of taste.
Ultimately, omicron symptoms may largely overlap those caused by prior variants "because they are essentially doing the same thing," Otto Yang, MD, an infectious disease physician at the University of California Los Angeles' David Geffen School of Medicine, told the Times. "If there are differences, they're probably fairly subtle."