Coronaviruses are a group of related viruses that cause disease in mammals and birds. In humans, these viruses infect the respiratory tract causing illnesses that range from mild to lethal. They are an extremely common cause of colds (which can also be caused by other viruses e.g. rhinovirus). More lethal variants include SARS (severe acute respiratory syndrome) and MERS (middle eastern respiratory syndrome).
The virus that causes covid-19 (coronavirus disease 2019) SARS-CoV-2 is a new strain that has not been previously identified in humans. As the virus is novel, we are racing to learn all we can about it whilst simultaneously implementing evidence-based plans to reduce transmission and manage cases. This is a global task- the entire population was vulnerable to this novel virus, which has enabled extremely rapid spread.