Why so many Covid-19 variants are showing up now

In November 2020, the UK's lockdown to control Covid-19 cases appeared successful overall, but infections in Kent continued to rise. Researchers later discovered that the virus in Kent had changed, becoming a new, more contagious variant that spread rapidly across England and globally, reaching 30 other countries in two months and becoming the most common form in the US within five months. More variants are now emerging worldwide.

Viruses are simple structures of protein and genetic material (DNA or RNA) with the sole goal of replication. They use host cells to copy their genetic code, but during this process, mistakes (mutations) occur. These mutations alter the virus's instructions, leading to a slightly changed virus, or variant. While most mutations are harmless or weaken the virus, some can give it an advantage, such as improved binding to human cells, as seen with the SARS-CoV-2 virus since December 2019.

Scientists observed that SARS-CoV-2 was evolving to bind human receptors and enter cells more effectively. The B.1.1.7 variant, later named 'Alpha,' had multiple mutations on its spike protein that enhanced its ability to bind to cells, making it more transmissible and leading it to become a dominant strain globally. This raised concerns about why these variants seemed worse now, given that mutations occur constantly.

Viruses don't make conscious decisions; mutations are random errors. However, the longer a virus circulates and the more people it infects, the more mutations accumulate. This accumulation increases the chances for the virus to evolve into something more dangerous. The four 'variants of concern' identified by the WHO, including Delta, all have mutations on the spike protein. The Delta variant, a 'double mutant,' possesses mutations that increase transmissibility and allow it to evade natural immune responses, potentially leading to re-infection.

Vaccine-induced immunity is stronger than natural immunity, making it unlikely that a variant will completely evade current vaccines. However, an extended pandemic with widespread replication cycles could allow the virus to evolve solutions to immunity from vaccination. To stop the emergence of new variants, the virus's spread must be halted globally. The existing vaccines remain effective against all current variants, but the slow global distribution of vaccines gives the virus more time to mutate and impact unvaccinated populations, underscoring that the pandemic is far from over.