Hello, Greetings! "All viruses, including SARS-CoV-2, the virus that causes COVID-19, change over time. Most changes have little to no impact on the virus’ properties. However, some changes may affect the virus’s properties, such as how easily it spreads, the associated disease severity, or the performance of vaccines, therapeutic medicines, diagnostic tools, or other public health and social measures. " https://www.who.int/en/activities/tracking-SARS-CoV-2-variants/ Most regilar details about Covid variants are given on above link, so no use to repeat here. However I just want to know more, what can be the main cause/s to getting variants of a virus?, Can it be due to:- 1. Evolution 2. Natural selection 3. Random mutations 4. Status of our Natural immune response 5. Our interventions(preventive or treatments 6. Other? All above or some of above should have been definately responsible for getting such variants which we can discuss. Best wishes.