Live updates: follow the latest news on Covid-19 variant Omicron
The Omicron variant of Covid-19 has spread rapidly throughout the world, leading many countries to reintroduce or tighten restrictions in an effort to slow its spread.
While initial evidence suggests Omicron may be less severe than previous Covid variants, it is believed to be more transmissible and more able to evade the protection offered by current vaccines.
What are the symptoms of the Omicron Covid variant?
In the UK, the National Health Service has said the main symptoms of Covid-19 are a high temperature, a new and continuous cough, and changes to people's sense of smell or taste.
But early signs suggest that there are other symptoms that may be more specific to the Omicron variant, including sneezing, fatigue, a headache, lower back pain, fever, scratchy throat, night sweats and a runny nose.
There are also signs that a changed sense of smell or taste is less likely to be a symptom, as has been the case previously.
How easy does Omicron spread?
Early research from experts in Hong Kong, based on lab testing of tissue samples, has shown Omicron replicates up to 70 times faster in the airways leading to the lungs than the Delta variant, which may help explain its rapid spread throughout the population.
But its apparent mildness may be explained by the same Hong Kong study that showed Omicron replicates 10 times slower in the lungs than Delta does.