A highly transmissible norovirus variant is making waves in the US and UK, causing concern among health officials.

Identified as GII.17, this strain triggered a spike in infections last year after it first surfaced in April, impacting both the US and Europe. Currently, the virus is on the rise again in the US, while in the UK, where it competes with the long-standing GII.4 variant, GII.17 is responsible for 19% of reported cases.

Health experts highlight the strain’s high contagion rate, and the Centers for Disease Control and Prevention have emphasized that it results in approximately 50% more infections than other norovirus types in the US, as noted by the Daily Mail.

Despite a decline in GII.17 cases in the UK, it remains the country’s second most prevalent strain, comprising 19% of cases as of December 7, according to the UK Health Security Agency. Meanwhile, the previously dominant GII.4 variant has regained prominence, accounting for 31% of cases for the 2025/2026 season up to December 7.

Nicknamed the ‘rib-cracking’ winter virus, this norovirus strain is notorious for causing such severe vomiting that it can lead to rib pain, as reported by HealthAndMe.

Infectious disease specialist Dr. Scott Roberts from Yale University explained to TODAY, “New strains often spread quickly, which is exactly what we observed last year.”

“So far, we’re not yet to the level that we were at last year, which was really our worst year since pre-Covid… but it’s certainly going up. Time will tell how bad it will get. Now is the time to be vigilant. I expect things to get worse before they get better.”

Norovirus, also known as the ‘winter vomiting bug’ is spread by close contact with an infected person or touching surfaces that have the virus on them and then touching your mouth. It can also be passed on by eating food that has been prepared by someone with norovirus.

If you get symptoms, the NHS recommends staying away from work or school for two days after the sickness and diarrhoea have passed.

It also highlights that fruit juice or fizzy drinks can exacerbate the sickness, and you should instead drink fluids such as water or squash.