The list of symptoms of Covid-19 has grown longer and stranger throughout the pandemic. With so many people now vaccinated, the warning signs of an infection have grown more subtle and vague. That’s becoming especially evident as the omicron variant gallops around the world, squeezing through the nooks and crannies in the wall of immunity that’s been built over the past two years.
An international team of researchers has been tracking signs of infection throughout the pandemic with the Covid Symptom Study using a mobile app where users could self-report their symptoms. Data on the omicron variant is still preliminary, but a group of 171 app users in the United Kingdom, most of whom are vaccinated, recently reported that their top symptoms for omicron were a runny nose, headache, fatigue, sneezing, and a sore throat. These were also the top symptoms for people infected with the delta variant.
That’s a departure from “the classic three” Covid-19 symptoms of fever, cough, and loss of sense of smell or taste associated with earlier variants, researchers say.
“For most people, an omicron positive case will feel much more like the common cold, starting with a sore throat, runny nose, and a headache,” Tim Spector, a professor of epidemiology at King’s College London and the lead scientist for the symptom study, told the BBC this week. ”We need to change public messaging urgently to save lives.”
Among the 171 people in the recent symptom data analysis who were suspected or confirmed to be infected with omicron by Britain’s National Health Service, the symptom study team found only half reported fever, cough, or a loss of taste or smell.
Researchers in Norway recently reported similar findings from an omicron outbreak among fully vaccinated guests of a Christmas party. In 87 confirmed or probable cases, the most common symptoms were cough, runny or stuffy nose, fatigue, sore throat, and headache. Just over half reported a fever, while 23 percent experienced a loss of taste and 12 had a decline in smell.
These cases are further evidence that the omicron variant is the most transmissible version of the virus so far, and it seems to be better able to evade prior immunity. Vaccines in the US still offer strong protection against severe illness, however, especially with a booster shot.
“We know we will continue to hear more about people who get infected who are vaccinated,” CDC Director Rochelle Walensky said at a White House press conference this week. “These people may get mild or asymptomatic infections and could unknowingly spread those infections to others.”
In South Africa, one of the first places where the omicron variant was detected, widespread vaccinations against the disease combined with some immunity from prior infection may explain why omicron seems to present with milder symptoms.
“We believe that it might not necessarily just be that omicron is less virulent, but we believe that this coverage of vaccination, also in addition to natural immunity of people who have already had contact with the virus, is also adding to the protection,” South Africa’s Health Minister Joe Phaahla told reporters last week. “That’s why we are seeing mild illness.”
In the US, 73 percent of the population has had at least one dose of a Covid-19 vaccine and more than 50 million people have been infected previously, so a significant portion of the population has some degree of protection against the disease.
Even so, some people with omicron will fall severely ill. According to the Centers for Disease Control and Prevention, the Covid-19 symptoms that demand emergency medical care include sudden confusion; inability to stay awake; persistent chest pain or pressure; trouble breathing; and lips, fingernail beds, and skin turning blue, pale, or gray.
While a smaller percentage of the infected get sick enough to go to the hospital, the overall increase in cases from omicron could result in enough illness to overwhelm the US health care system in the coming months.
In addition, severe illnesses often start out with mild symptoms, and many Covid-19 treatments are most effective in the early stages of the disease. The Food and Drug Administration recently granted emergency authorization to the drug Paxlovid from Pfizer, the first oral antiviral to get a green light from the agency. It’s recommended for “mild-to-moderate” Covid-19 cases in people with risk factors for severe disease.
The emergence of the cold-like symptoms with the omicron variant means that getting tested to confirm whether someone is infected with Covid-19 is more critical than ever to slow the spread of the virus. For people with preexisting health conditions, identifying infections early is key to deploying effective treatments in time.
Frequent rapid testing for Covid-19 can catch omicron cases, though they tend to have lower accuracy compared to more expensive and time-consuming PCR tests. Many local health departments are scaling up their public testing systems, and the FDA has increased the number of rapid rests authorized for use. But in some areas, rapid tests remain scarce and too costly to use regularly.
So it’s crucial to take mild Covid-19 symptoms seriously and just as important to prevent infections in the first place. That requires getting vaccinated against Covid-19, getting a booster dose if eligible, wearing an effective face mask in public settings, and social distancing. Despite the latest twists in the pandemic, these measures remain the best bets for keeping the virus in check.