COVID-19 infection is caused by the novel coronavirus SARS-CoV-2 and has become a global pandemic since its emergence in late 2019. The virus primarily spreads through respiratory droplets and can cause a range of symptoms, from mild respiratory issues to severe pneumonia and death. Research into COVID-19 infection focuses on understanding how the virus spreads, identifying risk factors for severe illness, developing diagnostic tests and treatments, and developing vaccines to prevent future infections. Current efforts are also focused on studying the long-term effects of COVID-19, known as "long COVID," and investigating how the virus may mutate and impact future waves of the pandemic.