Norovirus, often dubbed the 'winter vomiting bug', is a formidable and highly contagious stomach bug that strikes an estimated 684 million people globally every year. This family of viruses, comprising about 50 different strains, leads to a severe and unpleasant bout of infectious gastroenteritis, forcing sufferers into a miserable cycle of vomiting and diarrhoea.
How Does Norovirus Spread So Easily?
The virus is notoriously contagious, requiring a minuscule dose to cause infection. It typically spreads via the 'faecal-oral route', where tiny viral particles from an infected person's saliva or faeces contaminate hands, food, or surfaces. "The infectious dose of noroviruses is less than 20 virus particles," explains Dr Laraine Washer, a medical director at the University of Michigan. This is a stark contrast to Covid-19, which requires hundreds of particles.
These resilient particles can survive on hard surfaces like doorknobs for up to two weeks. People become contagious about two days before symptoms appear and can remain so for days or even weeks after recovery. Close-contact environments like care homes, nurseries, airports, and—infamously—cruise ships are hotspots for outbreaks. The US Centers for Disease Control and Prevention (CDC) has already reported 16 norovirus outbreaks on cruise ships in US ports in 2025 alone.
Recognising and Responding to Symptoms
Symptoms often begin abruptly with abdominal cramps, chills, nausea, and progress to forceful vomiting and watery diarrhoea. While most cases are medically considered mild and resolve within 72 hours, the experience is profoundly debilitating. Dr Ambreen Allana, an infectious disease physician, notes that sufferers often feel completely wiped out with fatigue and low-grade fever.
Most healthy adults and older children recover at home without medical intervention. The key is aggressive hydration with fluids like water, oral rehydration solutions, or ice lollies. "Try drinking the same amount of Gatorade or water as the volume that comes out," advises Dr Allana. Anti-nausea medication may help keep liquids down, but anti-diarrhoea medicines like Imodium should be avoided as they can prolong the infection.
However, norovirus causes 70,000 hospitalisations and 570-800 deaths annually in the US, primarily among the very young, the elderly, and the immunocompromised. These groups are at high risk of dangerous dehydration and kidney injury. If a high-risk individual cannot keep fluids down, seeking medical care for intravenous (IV) fluids is crucial.
Prevention is Your Best Defence
There is currently no vaccine for norovirus, due to its many strains and frequent mutations. Prevention therefore hinges on rigorous hygiene and cleaning practices.
Handwashing is paramount. Alcohol-based hand sanitisers are ineffective against norovirus. The CDC and experts like Dr Allana stress washing hands thoroughly with soap and water for at least 20 seconds. Infected individuals should not prepare food for others.
Cleaning requires potent chemicals. Surfaces should be disinfected with a diluted bleach solution (one cup per gallon of water) or undiluted 3% hydrogen peroxide. Most common disinfectant wipes are not strong enough. When doing laundry, use hot water and bleach if possible, as the virus can survive temperatures up to 70°C (158°F).
During peak season (December to February in the UK), consider avoiding high-risk settings like buffets and potlucks where many people handle serving utensils. If someone in your household is ill, designate a separate bathroom if possible.
Finally, do not assume prior infection grants lasting immunity. "We don't develop robust memory immunity to norovirus," says immunologist Dr Andrea Love. "People can become infected by norovirus every few months." Constant vigilance with hygiene remains the most effective shield against this pervasive winter bug.
