What is a coronavirus?
Coronaviruses form a large family of viruses that can cause a range of illnesses. They include the common cold as well as more serious diseases such as SARS (severe acute respiratory syndrome), MERS (Middle East respiratory syndrome) and, more recently, COVID-19.
Coronaviruses have been around for many years so humans have built up a general immunity to them. This means when we get a common cold, it is usually not very severe.
However, coronaviruses are not just present in humans. Many animals develop coronavirus-related illnesses and sometimes those viruses can mutate and be passed on to humans. When this happens, the disease can be more severe because the human body has not had to fight the illness before. SARS, MERS and COVID-19 are examples of this happening in recent years.
When a new strain of coronavirus is discovered, it is called a ‘novel' coronavirus.
Different types of coronavirus
A cold is a very common viral infection that affects the nose, throat and upper airways.
Learn more about COVID-19, including when to get tested or self-isolate, symptoms, how to avoid infection, physical distancing and restrictions.
Severe acute respiratory syndrome (SARS) is a virus that can cause severe pneumonia.
Middle East respiratory syndrome (MERS) is a disease that can cause fever, cough, shortness of breath and pneumonia in infected people.
Colds and flu symptoms can be very similar to the symptoms of COVID-19. Even if your symptoms are mild, get tested for COVID-19 immediately — use the colds and flu Symptom Checker if you're not sure what to do.
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Last reviewed: December 2021