With its rapid emergence, prolific spread and high number of breakthrough cases, omicron has shaken providers and citizens worldwide. Individuals infected with the variant have reported a wide range of symptoms, from nothing to seemingly every common cold symptom in the book.
"This is a pretty different surge," Brendan Carr, MD, chair of emergency medicine for New York City-based Mount Sinai Health System, told NPR.
Here's what we know:
The beginning
With omicron, symptoms likely come on more quickly once infected. Several preliminary studies have found that the incubation period — the time it takes to develop symptoms after being exposed — is about three days, shorter than any variant yet. A shorter incubation period often means someone infected becomes contagious faster. The incubation period is estimated to be about five to six days for the original strain, five days for the alpha variant and four days for delta.
Omicron has a much higher rate of asymptomatic spread than other variants, according to early findings published Dec. 27 by preprint server MedRxiv.
Symptoms
Many patients with omicron have a variety of symptoms that resolve quickly and don't require hospital care, NPR reported. Physicians told the news publication that omicron cases frequently look like ordinary upper respiratory infections.
"It's mostly that runny nose, sore throat and nasal congestion," John Vanchiere, MD, PhD, associate director of the Center for Emerging Viral Threats at Ochsner LSU Health Shreveport (La.), told NPR. "The cough is milder [than previous variants], if there's any cough at all, and fever seems to be a little less common."
The four most common symptoms of the omicron variant are cough, fatigue, congestion and runny nose, according to a CDC analysis of the first 43 cases investigated in the U.S. The CDC's list of COVID-19 symptoms includes fatigue, muscle or body aches, headache, sore throat, congestion or runny nose, nausea or vomiting, and diarrhea. Asymptomatic infections are also common. Early data from the U.K. found fever and cough aren't as prevalent with omicron, finding the five most common symptoms to be runny nose, headache, fatigue, sneezing and sore throat.
Sore throat may be a predictor of omicron among mild breakthrough cases, NBC Chicago reported Jan. 11.
Hospitals are seeing more patients now compared to earlier surges have milder symptoms and are seeing more incidental discovery of the disease, Cesar Arias, MD, PhD, chief of the division of infectious diseases at Houston Methodist Hospital and co-director of the Center for Infectious Disease Research at the system's research institute, told Becker's.
Mild omicron cases look like a bad cold, Dr. Arias said, noting that headache seems to be prominent, along with some sort of malaise and cough. He specified that the cough is typically a dry cough, very rarely a productive cough. Shortness of breath is not as prominent as it previously was for mild cases, according to Dr. Arias.
Unvaccinated individuals appear to experience symptoms similar to those seen early in the pandemic, said Allison Arwady, MD, commissioner for the Chicago Department of Public Health, according to NBC Chicago.
Severe cases
Severity varies by individual, depending on many factors, including vaccination status, age, overall health and socioeconomic factors.
A study involving nearly 70,000 COVID-19 patients at Kaiser Permanente of Southern California found patients with omicron infections were less likely to be hospitalized for COVID-19, and when they were, they had shorter hospital stays.
"In the older age group, it's still a nasty disease, even if it's less [nasty] than the delta variant," Pamela Davis, MD, PhD, a pulmonologist at Cleveland-based Case Western Reserve University, told NPR. "You don't get off scot-free just because you happen to be infected in the time of omicron."
Dr. Arias has seen severe presentation of the disease particularly in high-risk patients, such as immunocompromised individuals, the elderly or someone with one or more comorbidities. Most severe cases are definitely among the unvaccinated, he said. Dr. Arias emphasized the clear effect vaccination status has on severity, noting that even patients without a booster fare much better than those without any vaccination.
Among patients with severe omicron cases, their main complaint has been fever and respiratory symptoms that require some sort of oxygen, Dr. Arias said.
Recovery
"Those with a mild case of COVID-19 usually recover within one to two weeks," said Lisa Maragakis, MD, senior director of infection prevention for Baltimore-based Johns Hopkins Medicine.
"For severe cases, recovery can take six weeks or more, and there may be lasting damage to the heart, kidneys, lungs and brain," Dr. Maragakis said.
Most omicron patients don't end up requiring intensive care, Dr. Arias said, noting that when they do, they most likely have multiple comorbidities or other illnesses that require attention. Dr. Arias credited increasing knowledge of the disease and experience treating COVID-19 patients, saying most patients don't progress to the ICU.
There's still much unknown about long-haulers, or those who had COVID-19 and then experience persistent, recurring or reappearing symptoms four or more weeks after first being infected.
Conclusion
Speaking with Becker's at the end of a long shift, Dr. Arias asked that this piece emphasize the importance of vaccination. Vaccination against COVID-19 helps healthcare workers treat patients more quickly, and, beyond that, more successfully, Dr. Arias said. Vaccination clearly plays a role in disease presentation and severity. The ask feels small when considering the alternative potential hospital stay.