Norovirus: Understanding its transmission and prevention in the UK

Introduction 
Norovirus is recognised as the leading cause of viral gastroenteritis in the United Kingdom, responsible for over 50% of all gastroenteritis outbreaks¹. Often termed the “winter vomiting bug,” norovirus poses significant challenges due to its high infectivity and environmental resilience. 

Virology and infectivity 
Norovirus belongs to the family Caliciviridae and is a non-enveloped, single-stranded RNA virus². Remarkably infectious, as few as 10 to 100 viral particles can cause infection in humans^3,4. Its incubation period ranges from 12 to 48 hours, with symptoms typically lasting one to three days⁵. 

Transmission routes 
Transmission of norovirus primarily occurs via the faecal-oral route⁶: 

• Person-to-person contact: Direct interaction with an infected individual facilitates spread⁷. 

• Contaminated food and water: Ingestion of virus-laden food or beverages⁸. 

• Fomites: Contact with contaminated surfaces can lead to hand-to-mouth transfer⁹. 

• Aerosolisation: Vomiting can aerosolise viral particles, leading to inhalation and subsequent ingestion¹⁰. 

Environmental persistence 
Norovirus exhibits remarkable stability in the environment. Studies have shown that it can survive on surfaces for up to two weeks and remain viable in water for several months¹¹. The virus is resistant to common disinfectants and can withstand a range of temperatures and pH levels¹². 

Hand transfer and surface contamination 
Contaminated hands can transfer norovirus to up to seven clean surfaces, perpetuating the cycle of infection¹³. This highlights the critical role of hand hygiene and environmental cleaning in controlling outbreaks. 

Hand hygiene: limitations of alcohol-based hand rubs 
While alcohol-based hand rubs (ABHR) are effective against many pathogens, they are less effective against non-enveloped viruses like norovirus^14,15. The lipid envelope targeted by alcohol in enveloped viruses is absent in norovirus, reducing ABHR’s virucidal activity. 

Importance of hand washing with soap and water 
The UK Health Security Agency (UKHSA) and World Health Organization (WHO) recommend thorough hand washing with soap and water as the most effective method for removing norovirus from hands.^16,17 Mechanical action during hand washing helps dislodge and rinse away viral particles. 

Surface disinfection 

Efficacy of disinfectants 
Effective disinfection requires agents that are proven to inactivate norovirus. Disinfectants should meet the requirements of the European Standard EN 14476, a prescribed method of demonstrating effective virucidal activity against norovirus under dirty conditions (i.e., in the presence of organic matter) and with realistic contact times¹⁸. 

Clinell Universal Wipes: Meeting EN 14476 Standards 
Clinell Universal Wipes are combined detergent and disinfectant wipes that have shown efficacy against norovirus. They comply with EN 14476 under dirty conditions with a contact time of 60 seconds¹⁹. This makes them a practical choice for surface decontamination in both healthcare and community settings. 

Preventive measures 

Hand hygiene practices 

• Wash hands frequently with soap and water for at least 20 seconds, especially after using the toilet and before eating or preparing food¹⁶. 

• Avoid relying solely on ABHR, especially during norovirus outbreaks. 

Environmental cleaning 

• Use disinfectants effective against norovirus, ensuring they meet EN 14476 standards¹⁸. 

• Pay special attention to high-touch surfaces like door handles, taps, and toilet flush handles²⁰. 

Isolation and exclusion 

• Exclude symptomatic individuals from work, school, or social gatherings until 48 hours after symptoms have resolved²¹. 

• In healthcare settings, isolate infected patients to prevent nosocomial transmission²². 

Food safety measures 

• Implement strict hygiene protocols in food handling and preparation⁸. 

• Ensure shellfish and other high-risk foods are cooked thoroughly to inactivate the virus. 

Conclusion 

Norovirus remains a formidable public health challenge due to its high infectivity and environmental robustness. Emphasising the limitations of ABHR against norovirus, it is imperative to promote hand washing with soap and water and the use of effective disinfectants that meet EN 14476 standards. Through diligent hygiene practices and appropriate environmental cleaning, the spread of norovirus can be significantly mitigated.