The UK is experiencing a concerning surge in a highly contagious new Covid variant, officially named N.B.1.8.1, but popularly dubbed 'Nimbus'. Official data from the UK Health Security Agency (UKHSA) indicates a rapid increase in its prevalence, with the proportion of Covid tests positive for Nimbus doubling from just four percent in mid-May to eight percent by early June. This variant is feared by experts to be the most contagious strain yet, potentially driving a new wave of cases this summer across the nation.

Beyond Nimbus, the overall trend of Covid-19 infections is also escalating. UKHSA data for June 15 revealed that the total number of tests returning positive for any Covid variant had risen to 6.8 percent, up from 5.6 percent the previous month, marking the highest figure recorded this year. These figures, however, are likely an underestimate given the significant reduction in Covid testing since the peak of the pandemic. Coupled with rising infections, there has also been a slight increase in Covid-related hospital admissions, reaching just over 1.5 admissions per 100,000 people. The virus was also recorded as a factor in the deaths of 68 people in England in the week leading up to June 6.

British scientists have voiced concerns that the rise of Nimbus is exacerbated by declining public immunity. Many people's protection, built up from prior infections and older vaccine doses, has likely faded, increasing their susceptibility. Lab studies support these warnings, suggesting that Nimbus is not only more efficient at infecting human cells but also possesses an enhanced ability to evade the immune system, making reinfection more probable.

Despite its heightened transmissibility, there is currently no evidence to suggest that Nimbus, a descendant of the Omicron variant, causes more severe illness or death compared to previous strains. However, medical professionals reiterate that any Covid infection can still be dangerous, particularly for vulnerable populations such as the elderly or those with compromised immune systems.

Symptoms associated with the Nimbus variant generally align with those of other Covid strains, including fatigue, fever, muscle aches, and a sore throat. However, medics have highlighted a particularly striking symptom: a "razor blade" sore throat, which can feel like a sharp, stabbing pain when swallowing. Other distinct signs include swollen neck glands and redness in the back of the mouth. A new or persistent cough, characterized by three coughing episodes in 24 hours or prolonged coughing for over an hour, along with a high temperature or shivering chills, are also strong indicators. Other potential symptoms encompass a loss or change to sense of smell or taste, shortness of breath, a runny nose, body aches, headaches, loss of appetite, diarrhoea, vomiting, and nausea.

Regarding protection, current Covid vaccines, which have been reformulated to target Omicron descendants, are anticipated to remain effective against Nimbus. Vaccine manufacturers are actively updating their shots to specifically combat the Nimbus strain, with Moderna announcing its updated mNEXSPIKE shot will be available by the fall. However, recent UKHSA data on vaccine uptake in England reveals a concerning trend: only 59 percent of Britons aged over 75 have received a Covid vaccine, and this figure plummets to just one in four among under 75s with compromised immune systems, despite their eligibility for the jab on the NHS. NHS England's spring Covid vaccine drive recently concluded.

Globally, Nimbus is expanding its footprint, now accounting for 10.7 percent of Covid infections worldwide, a significant jump from 2.5 percent in May. The variant first emerged in China, where it has been linked to an uptick in cases and emergency department visits. It has also gained considerable traction in the United States, where it constitutes over a third of Covid cases, making it the second most common variant. Interestingly, the name 'Nimbus' was coined by Canadian evolutionary biologist T Ryan Gregory, known for naming many popular Covid strains. In the UK, while Nimbus is on the rise, it still accounts for a minority of total Covid cases, with LP.8.1.1 and XFG, also Omicron descendants, being the most common variants circulating.