Why people are getting norovirus twice

Independent

27-02-2025

Known for its rapid spread and stomach-churning symptoms, norovirus has long been a common culprit behind wintertime stomach bugs.
However, health officials are now warning the public about the potential for a 'second norovirus wave', as reports suggest that more individuals are contracting the vomiting bug more than once.
The UK Health Security Agency (UKHSA) has noted that those who've already battled the virus this winter may be at risk of reinfection due to multiple strains.
To shed light on this growing concern, we spoke to a GP who has explained why people could get norovirus more than once…
What is norovirus?
' Norovirus is a highly contagious virus that causes vomiting and diarrhoea, often referred to as the 'winter vomiting bug',' says Dr Chun Tang, GP at Pall Mall Medical. 'It spreads like wildfire, usually through contaminated food, water, surfaces, or direct contact with an infected person.'
According to the NHS website, the primary symptoms include sudden nausea, vomiting, and diarrhoea. Patients may also experience a high temperature, headaches and stomach pains.
'It usually comes on very quickly, making you feel awful for a couple of days, but most people recover without any complications,' says Tang. 'The biggest risk is dehydration, so staying hydrated is key.'
Why are people getting it twice?
'Unlike some viruses, norovirus doesn't give you long-term immunity,' explains Tang. 'There are many different strains, so even if you've had it before, you can still catch a different version of it.
'Plus, any immunity you do develop is short-lived, which means you can get sick again.'
The two primary norovirus strains circulating in the UK at the moment are the GII.17 genotype, which is believed to be responsible for the surge in cases this winter, and the GII.4 strain.
New UKHSA data shows that while the GII.17 genotype remains dominant, accounting for 59% of cases, its prevalence has dropped from 76% since November.
Meanwhile, the GII.4 strain has seen a sharp rise, now representing 29% of cases compared to just 10% three months ago.
What is the difference between the GII.17 and the GII.4 strain?
'The GII.4 strain has historically been the dominant one, causing most outbreaks,' notes Tang. 'However, the GII.17 genotype has been increasing in some parts of the world, and researchers think it may behave slightly differently in terms of how our immune systems respond to it.
'The recent sharp rise in GII.4 cases suggests it may have mutated again, making it more infectious or better at evading immunity.'
Who is more at risk?
Children younger than five years old, older adults, and people with weakened immune systems are more likely to develop severe infections, according to the Centers for Disease Control and Prevention website.
'This is because [these groups] struggle to stay hydrated, which is the biggest danger with norovirus,' explains Tang. 'For babies and the elderly, dehydration can lead to hospitalisation if it's not managed properly.'
How contagious is it?
'Norovirus spreads through tiny particles in vomit and stool, which can linger on surfaces or even in the air after someone vomits,' highlights Tang. 'You only need a few viral particles to become infected, which is why outbreaks happen so quickly in shared spaces.'
Can it be treated?
'There's no specific treatment for norovirus – it's all about resting, staying hydrated, and letting your body fight it off,' says Tang.
A common misconception is that alcohol hand gels kill norovirus.
'They don't,' clarifies Tang. 'Norovirus is resistant to alcohol, so washing your hands thoroughly with soap and water is the best way to prevent its spread.'
Should people go to the doctors about norovirus?
Most people don't need to see a doctor and can recover at home with rest and fluids.
'However, if you're struggling to keep fluids down, showing signs of severe dehydration (like dizziness, confusion, or very little urination), or have a baby or elderly person who seems particularly unwell, it's best to seek medical advice,' advises Tang.
What can you do to prevent yourself from catching it?
'The best prevention is good hygiene – wash your hands properly with soap and water, especially after using the bathroom or before preparing food,' recommends Tang. 'Also, avoid close contact with sick people and disinfect surfaces regularly.
'If you do get norovirus, stay home for at least 48 hours after symptoms stop to prevent spreading it to others.'