A sub-variant of the Omicron strain of coronavirus has been classified as a “variant of interest” by the World Health Organization, because of “its rapidly increasing spread”.
JN.1 has been found in many countries around the world, including India, China, UK and the United States.
The risk to the public is currently low and current vaccines continue to offer protection, the WHO says.
But it warns Covid and other infections could rise this winter.
Respiratory viruses such as flu, respiratory syncytial virus (RSV) and childhood pneumonia are also on the rise in the northern hemisphere.
The virus which causes Covid is constantly changing over time and sometimes this leads to new variants developing.
Omicron has been the globally dominant variant for some time.
The World Health Organization (WHO) is currently tracking a number of variants of interest linked to Omicron – including JN.1 – although none of them are deemed to be concerning.
But JN.1 is spreading quickly in many corners of the world.
It is currently the fastest-growing variant in the United States, according to the US Centres for Disease Control and Prevention, accounting for 15-29% of infections.
The UK Health Security Agency says JN.1 currently makes up around 7% of positive Covid tests analysed in a lab. It said it would continue to monitor all available data on this and other variants.