The United States’ leading COVID-19 advisor, Dr Anthony Fauci,  warned the country to brace for a fresh surge of infections that could see cases double as fall and winter approach, fuelled largely by the incessant spread of the Delta variant. 

Over the last few weeks and months, the variant has torn through cities and towns in the US, putting paid to previous predictions of an exit out of the pandemic, and prompting Dr Fauci to caution, “We’re now dealing with, really, a different virus.” 

The world has been grappling with COVID-19 for over twenty months now and the development of a slew of vaccines is testament to how much we’ve learnt of the virus so quickly. But it’s safe to say that, with the emergence of so many new worrying variants, scientists have been caught off guard. 

With COVID-19 being an entirely unknown pathogen, epidemiological experts only had our previous experiences of coronaviruses to fall back on when predicting the threat borne out of SARS-CoV-2 mutations. But although the mutation rate of COVID-19 has been slow, the sheer scale of the outbreak, and the sizes of the populations that remain susceptible to infection, afford the virus a dangerous advantage. 

Having now entered August, the World Health Organisation is specifically monitoring variants like Eta, Kappa, Iota, Lambda and Delta, among others. Lambda has already become the most dominant strain in South America and has recently been found in Texas and South Carolina in the US as well. But the rate at which the Delta variant has spread, first in the UK and now in the US has scientists concerned that, given persistent low rates of vaccination, we may forever be one step behind the virus. 

Unlike other pathogens like E.coli, the COVID-19 virus only has about 15 genes that it can scramble to produce fresh mutations. What’s more, research has shown that the virus has fairly effective genetic verification mechanisms that reduce errors in replication. 

But while those factors may mean that the rate of COVID-19’s mutation may be low, the number of copies the virus makes in a human body can run up to 10 billion – enough to produce billions of mutations. Most of these mutations are harmless but every now and then, one arises that is capable of out-competing others for dominance, potentially triggering a fresh outbreak. 

In order to achieve this, a variant will, ordinarily, need to adapt features that allow it to travel further distances in the air or latch more firmly in people’s nasal passages so as to boost transmissibility. As more people get vaccinated, the chances of such variants spreading fall, but those who remain unvaccinated continue to serve as mutation labs for the new variants. 

A virus’ ability to evade the human body’s immune response doesn’t necessarily make it more dangerous, and there is some optimism to be had in the studies showing that, despite vaccines being found to be significantly less effective against some strains, they remain effective in preventing serious infection. Real-life studies showing higher rates of vaccine effectiveness than those found in clinical settings also indicate that our bodies have a series of weapons that improve our ability to stave off the virus beyond just COVID-19 antibodies. 

Still, scientists remain concerned that the Delta variant – now believed to be the most transmissible – does not necessarily represent a ceiling of infectiousness. A variant with even greater transmissibility capabilities making its way through an unvaccinated cluster could yet spell more misery, leading to healthcare infrastructure being stretched even further. 

There is also a worry that the virus may mutate to affect different parts of the body (apart from the lungs), causing a potential scenario where symptoms are delayed. If this does indeed manifest, asymptomatic carriers will continue to unwillingly spread the virus. 

The composition of the virus does suggest that, at some point, it will effectively run out of ways to become more potent or aggressive. After all, the simple nature of its spike protein indicates that it can only mutate a few hundred times, most of which are harmless. But in the face of trailing vaccination rates, its capacity to haunt populations will endure, and the possibilities of future, more dangerous variants cannot be ruled out.