UK Health Officials Warn of Second Norovirus Wave

Norovirus cases in England have continued to surge, with laboratory reports at their highest levels since current records began in 2014, according to the UK Health Security Agency (UKHSA). 

An average of 1134 patients were hospitalised daily with norovirus last week. While slightly lower than the previous week’s 1160, this remains nearly two and a half times higher than the same period last year, when the average was 470.

Between 3 and 16 February, laboratory-confirmed cases were 29.4% higher than the previous fortnight and more than double the five-season average for the same period, UKHSA data showed.

“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,” said Amy Douglas, lead epidemiologist at UKHSA, in a statement. “We are seeing the biggest impacts in health and social care settings, such as hospitals and care homes,” she added.

Professor Arlene Wellman, group chief nurse for St George’s, Epsom and St Helier, warned that once norovirus enters a hospital, it can spread rapidly. “It can rip through our wards like wildfire, making patients even sicker,” she told the Science Media Centre (SMC).

Potential Second Wave Driven by Multiple Strains

The increase in cases this season has been associated with the recent emerged of the GII.17 genotype. However, the latest data showed that another common strain, GII.4, is now increasing. 

Before GII.17 emerged, GII.4 was the dominant strain, typically increasing each winter. 

Dr Damien Tully, associate professor in bioinformatics at the London School of Hygiene & Tropical Medicine, explained that GII.17 had been responsible for only 1% of cases in the past 7 years.

Although GII.17 remains the most common strain, accounting for 59% of cases, its prevalence has declined from 76% since November. Meanwhile, the GII.4 strain has risen sharply, now accounting for 29% of cases – up from just 10% 3 months ago, the UKHSA reported.

People who have already had norovirus this season could be reinfected, as immunity to one strain did not fully protect against others, the agency warned.

Paul Hunter, professor in medicine at the University of East Anglia, noted that a double peak in norovirus cases is “not unusual”. He told the SMC that it was “the norm” to see two different strains within a season, “though one tends to predominate”.

According to Tully, “The second wave, while a cause for concern, should not be entirely surprising, as the GII.4 strain has dominated for over a decade and is a tough competitor.” He added: “Time will tell if the new GII.17 variant – which was evolving between three and six times faster compared to other GII.17 variants – can end GII.4’s 12-year reign as the dominant strain.”

Hospitals Under Pressure

Hunter suggested that the sharp rise in cases could be partly due to increased testing. “Testing for norovirus has become increasingly common in recent years as a result of new technology, and so some of this increase will be an artifact of increased testing,” he suggested. He also noted that low population immunity, following reduced exposure due to COVID-19 measures, may be contributing to the surge.

“Given the current variant’s low prevalence over past years, most people are susceptible to infection, which explains the huge surge in cases,” Tully underlined. 

Hospital capacity remains under strain, with 95.3% of adult beds occupied last week and an average of 96,807 patients in hospital each day, the UKHSA reported.

“NHS wards are full to the brim with barely any spare beds,” Saffron Cordery, interim chief executive of NHS Providers, said in statement. “A tough situation is being made even tougher, with far too many patients stuck in hospital – almost one in seven – who are well enough to go home but can’t, often due to pressures on social and community care services,” she added. 

Dr Rob Hicks is a retired NHS doctor. A well-known TV and radio broadcaster, he has written three books and has regularly contributed to national newspapers, magazines, and online. He is based in the UK.