The COVID-19 pandemic or 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 Wuhan, China, in December 2019; a lockdown in Wuhan and other cities in Hubei province failed to contain the outbreak, and it 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. Since 2021, variants of the virus have emerged and become dominant in many countries, with the Delta, Alpha and Beta variants being the most virulent. As of 26 September 2021, more than 231 million cases and 4.74 million deaths have been confirmed, making it one of the deadliest pandemics in history. COVID-19 symptoms range from unnoticeable to life-threatening. Severe illness is more likely in elderly patients and those with certain underlying medical conditions. The disease transmits when people breathe in air contaminated by droplets and small airborne particles. The risk of breathing these in is highest when people are in close proximity, but the virus can transmit over longer distances, particularly indoors. Transmissi... ()