The United Kingdom is facing alarming surges of norovirus cases, prompting health authorities to issue warnings about the potential for multiple reinfections among the population. The UK Health Security Agency (UKHSA) recently reported unprecedented levels of norovirus activity, marking the highest numbers since systematic tracking began in 2014.
Between February 3 and 16, 2025, laboratory-confirmed norovirus cases rose sharply by nearly 30%, doubling the five-season average for the same period. Notably, the rise of infections has been particularly severe within hospitals and care homes, where older adults—especially those aged 65 and over—are being most affected.
Dr. Toyin Ejidokun, consultant in health protection at UKHSA South West, expressed concern over the current state of outbreaks, noting, "Norovirus levels are still exceptionally high and now with multiple genotypes spreading at the same time, people could end up getting infected more than once this season." This reflects the dual emergence of two distinct norovirus strains: the long-standing GII.4 genotype and the newly dominant GII.17 strain, which has made headlines for its rapid transmission.
Norovirus, often referred to as the "winter vomiting bug," typically results in abrupt symptoms like vomiting, diarrhea, and stomach cramps. These symptoms usually develop one to two days post-infection and can vary significantly, particularly among vulnerable individuals, where severe cases can lead to rapid dehydration and hospitalization.
Dr. Damien Tully, an associate professor at the London School of Hygiene & Tropical Medicine, elaborated on the strain shift, explaining, "Since 2012, there has been one dominant norovirus variant circulating in the UK called GII.4. The surge this season is attributed to GII.17, which was previously responsible for only about 1% of cases over the last seven years. Given the current variant's low prevalence, most people are susceptible to infection, which explains the surge." Tully emphasizes how the decline of previous exposure due to COVID-19 measures has likely fueled the rapid spread of these genetically distinct strains.
The UKHSA's data show GII.17 now accounts for approximately 59% of all norovirus cases, yet its prevalence has declined from 76% earlier this winter. Meanwhile, GII.4 is making its comeback, rising to 29% of cases—a sharp increase from 10% just three months prior. This trend suggests the potential for a double peak of norovirus infections, which is not uncommon as competing strains circulate, particularly with one often dominating the others.
Despite the challenges posed by these fast-evolving viruses, Dr. Tully remains cautiously optimistic about the potential for future vaccination efforts. Research to understand the genomic evolution of norovirus not only aims to tackle the current outbreak but may also lead toward developing effective vaccines. "Uncovering the clues to norovirus's success will help us understand how to potentially create vaccines, hopefully within close reach," Tully noted.
Heightened public health measures are advised as the season progresses. Dr. Amir Khan, speaking on Good Morning Britain, highlighted the ineffectiveness of alcohol hand sanitizers against norovirus. He warns, "Norovirus particles are extremely infectious even at low doses, which makes proper handwashing after restroom use and before food preparation imperative." Sanitizing surfaces with bleach or disinfectants is also recommended to combat the virus, which is known for its resilience and ability to survive on surfaces for days.
Families are urged to practice strict hygiene protocols, particularly during this contagious winter season. The UKHSA's warnings suggest avoiding contact with those displaying symptoms and adhering to isolative precautions until 48 hours after symptom resolution.
Hospital systems are currently under increased stress, with recent reports indicating 95.3% of adult beds were occupied last week, and nearly 1,135 patients were hospitalized daily with norovirus. "The situation is grim, with many hospitals facing double pressures from increasing cases and patient overflow," noted Saffron Cordery, interim chief executive of NHS Providers.
With waves of norovirus continuing to pose threats, especially to the elderly and weakened immune systems, public awareness and preventive measures remain key to controlling the virus's spread among vulnerable populations. By embracing rigorous hygiene practices and remaining alert to symptoms, the community can help mitigate the impact of this contagious winter illness.