The COVID-19 pandemic, also known as the coronavirus pandemic, is an ongoing global pandemic of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The novel virus was first identified in the Chinese city of Wuhan in December 2019; a lockdown in Wuhan and other cities in surrounding Hubei failed to contain the outbreak, and it quickly spread to other parts of mainland China and around the world. The World Health Organization (WHO) declared a Public Health Emergency of International Concern on 30 January 2020, and a pandemic on 11 March 2020. Multiple variants of the virus have emerged and become dominant in many countries since 2021, with the Alpha, Beta, and Delta variants being the most virulent. As of 18 October 2021, more than 240 million cases and 4.9 million deaths have been confirmed, making it one of the deadliest pandemics in history.
COVID-19 symptoms range from none to life-threatening. Severe illness is more likely in elderly patients and those with certain underlying medical conditions. Transmission of COVID-19 occurs when people breathe in air contaminated by droplets and small airborne particles.