Health officials across the UK are grappling with an unexpected and early surge in cases of the highly contagious norovirus, a stomach bug known for causing severe vomiting and diarrhoea. Data from the US Centers for Disease Control and Prevention (CDC) indicates this year's peak has arrived weeks ahead of the typical post-holiday season schedule, leaving experts searching for answers.
An Unseasonal and Sharp Increase
The latest CDC figures reveal a significant jump in norovirus activity. For the week of November 22, 12.5 percent of tests came back positive, a rate similar to the 13 percent seen the week before. This represents a 25 percent surge compared to just two weeks prior, when one in ten tests were positive. Crucially, outbreaks reported between August 1 and November 13 this year have more than doubled, reaching 153 compared to 69 during the same period last year.
Norovirus typically thrives in winter, with cases spiking after Christmas and New Year gatherings. "Norovirus thrives in winter and as people move indoors and mix more closely so transmission becomes far easier," explained Dr Olalekan Otulana, a physician at Cassiobury Court in the UK. The current early spike, without a clear reason, has taken experts by surprise and could disrupt upcoming festive plans.
Potential Causes and Public Health Impact
Experts suggest a combination of factors may be behind the premature surge. Dr Otulana pointed to "seasonal factors and shifting immunity patterns," noting that yearly variations in circulating virus strains can reduce prior immunity. A dominant strain known as GII.17 has become increasingly prevalent and is suspected to be a contributor.
"The two possibilities is that something in the virus changed to make it more transmissible, or there were changes in the population that a larger proportion were susceptible," said Dr Robert Atmar, a professor at Baylor College of Medicine. "And probably it’s a combination of both."
The true scale of infection is likely much higher than reported figures suggest. Norovirus affects an estimated 21 million Americans annually, with only a fraction seeking formal testing. In the UK, it is a major annual burden on the NHS. The virus is notorious for its rapid onset, with symptoms appearing 12 to 48 hours after exposure. While most recover within days, it causes around 900 deaths annually in the US, primarily among adults aged 65 and older, due to complications like severe dehydration.
Symptoms, Risks, and Prevention
Norovirus symptoms are violently abrupt, including projectile vomiting, diarrhoea, nausea, and stomach cramps. It can also cause fever, headaches, and body aches. The primary danger is dehydration from fluid loss, which can lead to dangerous electrolyte imbalances, low blood pressure, and in severe cases, seizures.
The virus spreads easily through contact with contaminated surfaces, food, or directly from an infected person. A key point for public awareness is that alcohol-based hand sanitisers are ineffective against norovirus. "The most effective protection comes from handwashing with soap and water, especially before eating and after using the toilet," stressed Dr Otulana.
With the holiday season approaching, health officials urge vigilance. The unusual timing of this surge serves as a stark reminder that this ultra-contagious bug requires robust hygiene practices to prevent its spread in homes, care settings, and at festive gatherings.
