Common coronaviruses are viruses that cause mild to moderate respiratory illness in humans and is often responsible for upper respiratory tract disease and the common, seasonal cold. Most people are infected with a common coronavirus during their lifetime and recover on their own without treatment. They are found worldwide in temperate and tropical countries, as well as low-, middle-, and high-income countries. HCoV infection can occur at any time of the year, with unpredictable year-to-year patterns, and outbreaks are reported in some years and in certain parts of the world. All common coronaviruses species may circulate yearly and even simultaneously, with the highest rates of HCoV infection seen in winter and spring months in temperate climates.