Last week new figures showed that Covid-19 infections in the UK increased by 43 per cent in the week after the platinum jubilee celebrations, with the two new sub-variants believed to be behind the sudden increase.
Additionally, around 1.4 million people in the UK had coronavirus in the week ending 11 June, up from around 990,000 the week before.
Speaking during a briefing by the Independent Scientific Advisory Group for Emergencies (Sage) in May, Professor Christina Pagel said: “The new wave is now starting.”
She added: “We will have a new wave of infections this month. Now hopefully it won’t be as high as the previous two waves and might be lower. But we can’t count on that and either way we are going to see more people becoming infected.”
Here are the most infectious Covid-19 variants since the pandemic first began:
The original virus:
The novel coronovirus SARS-CoV-2 first emerged in Wuhan, China in 2019. By March 2021, Covid-19 had spread across the world, causing national lockdowns and closing borders as the world faced a global health pandemic.
Currently, there are roughly eleven variants which are being monitored, including the well-known Alpha and Delta variants.
But the only strain which is currently a variant of concern comes from the Omicron family. This means it is more contagious, can cause more severe disease, and could be less susceptible to public health measures.
The Alpha variant was first detected in UK and a variant of concern in December 2020. By December 2021, it was identified in 192 locations worldwide.
The alpha variant has 17 mutations compared to the original Wuhan strain.
It is around 1.5 times more transmissible than earlier covid variants, and the risk of it leading to death is around 1.6 times higher, according to the BMJ.
Identified originally in India in late 2020, the Delta strain swept across the globe and is thought to have brought about the UK’s third wave in autumn 2021.
According to data analysed by ONS, the risk of death involving Covid-19 was estimated to be 67 per cent lower following Omicron infection compared to Delta - thereby, making Delta more deadly.
A study by The Lancet also found that the Delta variant might lead to a higher health-care burden than with the Alpha strain, as it reported that people in England had double the hospitalisation risk with Delta than with Alpha.
Omicron took hold in the UK at the end of 2021, dampening Christmas and New Year plans.
It was first detected in southern Africa in November 2021 and now has several subvariants, two of which are currently spiking concerns of another wave.
In mid-May, the UK Health Security Agency (UKHSA) elevated the classification of the Covid-19 variants Omicron BA.4 and Omicron BA.5 to variants of concern. Prior to this, BA.2 - also known as Stealth Omicron - was the prominent variant in the UK.
Omicron is more transmissible than the original virus first seen in Wuhan and Delta.
Its capacity to evade immunity may be because more than 30 of the variant’s mutations are on the virus’s spike protein which attaches itself to human cells.
However, the variant is generally milder than infections caused by the Delta variant, though it can still cause severe infections and death.
In a SAGE conference in January, they cited analysis from Imperial College London which suggests a reduction in risk of hospitalisation of 35-65 per cent for Omicron when compared to Delta in the most recent wave for those who had two doses of a vaccine.
Further, during the peak of the Omicron wave, researchers from Imperial found that the risk of reinfection with Omicron is 5.4 times greater than that of the Delta variant.
Lisa Maragakis, senior director of infection prevention at Johns Hopkins Hospital in Baltimore, said: “The omicron variant is responsible for the largest surge since 2019.”
The new BA.4 and BA.5 strains have more in common with the earlier, more dangerous Alpha and Delta variants because they may have evolved to refavour infection of lung cells, according to preliminary data from Kei Sato at the University of Tokyo and colleagues.
Whereas, the highly transmissible original Omicron targeted upper respiratory tract tissue, which may be why the infections tend to be milder in most people.