Like previous variants of COVID-19, Omicron has brought with it a new range of early-onset symptoms to watch out for, South African scientists say.
The new variant of the virus was first detected less than a month ago, but is already the dominant strain of the virus in London, is expected to take over from Delta in Europe by early 2022, and is threatening to break infection records wherever it shows up.
Data released by South Africa's largest private health insurance administrator Discovery Health on Wednesday (NZ time) found it was better able to infect vaccinated people than the Delta strain; and though a double-vaccinated person was still less likely to end up in hospital, protection dropped from 93 percent (against Delta) to just 70.
Discovery chief executive Ryan Noach has now revealed the data - covering 78,000 Omicron cases - show the earliest symptoms of an infection are slightly different to those of previous strains.
The most common is a scratchy throat, followed by nasal congestion, a dry cough and muscle aches in the lower back, The Telegraph reported.
UK analysis backed up the South African data.
"I think one of the things we do know is the clinical syndrome is rather different," University of Oxford chair of medicine Sir John Bell told BBC Radio 4. "The symptoms people get from this particular virus are different to the previous variants."
He said a "stuffy nose" was also common at the early stage of an infection.
People who contracted the original strain of COVID-19 which emerged in early 2020 often reported losing their sense of smell or taste before anything else.
Delta, which likely evolved in India in 2020 ahead of the nation's massive wave of infection in early 2021, brought early symptoms more like the common cold, with fewer experiencing a loss of sense of smell or taste.
Unvaccinated people seem to be more susceptible to early symptoms than vaccinated, South African doctor Angelique Coetzee told Sky News.
"Unvaccinated patients seem to experience the severity of the myalgia and headache more intensely than our vaccinated patients."
Early data has found Omicron appears to have a lower hospitalisation rate than Delta and other strains of COVID-19, but it's not clear yet whether that's because the virus itself isn't as virulent, or whether it's just struggling to break through people's immunity, whether from vaccines or prior infection.
While vaccines aren't as effective against Omicron, they still offer 70 percent protection against hospitalisation, the South African data shows.
"This is relatively good news, we might have easily seen a bigger drop," microbiologist Ravi Gupta of the University of Cambridge told The Telegraph.
But its extreme infectivity - some estimating it's four times as transmissible as Delta, which was catchy enough to end New Zealand's elimination strategy - means it still has the potential to overload countries' health systems.
"Even if omicron does cause less severe disease, the sheer number of cases could once again overwhelm unprepared health systems," Tedros Adhanom Ghebreyesus, head of the World Health Organization, said at a press conference.
He warned the variant was "probably in most countries" already, even if they hadn't yet picked it up.
WHO health emergencies director Mike Ryan said Omicron would be "very hard to stop", but trying to would at least slow it down so health systems can cope.
"Health systems are weaker now than they were a year ago in reality. So unfortunately, sometimes you can get up after the first punch, but it’s very hard to get up after the second. And that’s the difficulty. We’re relying on health workers of the health system that have been weakened by this response."
