How has SARS-CoV-2 evolved?
Viruses have existed for over 3.5 billion years, so where here long before humans! They have had a long time to evolve and like virtually everything in existence, their primary goal is to reproduce.
Because there has been such a big 'pool' of infectious people, the SARS-CoV-2 virus has had a lot of opportunity to mutate and become more efficient. This has resulted in new strains, that have become increasingly effective at infecting people so can spread faster, but thankfully this has resulted in milder symptoms.
There are hundreds of variations that have been identified globally and variants of concern are now being allocated letters from the Greek alphabet. The Alpha variant, is the original Wuhan or native strain and folliwing Beta, Gamma and Delta, the Omicron variant is currently the most dominant strain. There are several sub-variants of Omicron.
Recently recombinant variants have been identified, which you may have heard of such as XE. These are as a result of a person being infected with 2 or more sub-variants at the same time. This is not unusual given the amount of variants in circulation in such a large number of people.
How have COVID-19 symptoms evolved?
The symptoms identified from the original alpha strain included fever, sore throat, persistent cough, shortness of breath and one of the primary identifiers of infection was a loss of taste and smell (anosmia).
As the virus has evolved, so have the symptoms. Tiredness is still a key symptom, however headaches and a runny nose are now the main symptoms. Having a persistent cough and loss of taste and smell are reported far less.
Omicron has resulted in a far greater percentage of people having asymptomatic infection. This is when you have infection but do not have any symptoms. Some research suggests asymptomatic infection with Omicron could be as high as 53-70%.
Obviously there are far greater numbers of tests being performed, so there are far higher rates of diagnosis. There is also ongoing research around the impact of vacciantion on asymptomatic infection, as the vaccines can prevent COVID-19 disease but not SARS-CoV-2 infection.
People with asymptomatic infection can still spread the virus.