Since January 2020, Elsevier has created a free COVID-19 resource center with English and Mandarin information on the novel coronavirus. The center is hosted on Elsevier Connect, a public news and information website. Elsevier grants permission to make all its COVID-19-related research immediately available in PubMed Central and other public repositories for unrestricted research use. This review discusses the epidemiology, genetic recombination, and pathogenesis of human coronaviruses (HCoVs). HCoVs include those causing the common cold, SARS, and MERS. Dromedary camels in Saudi Arabia harbor three HCoV species, including a dominant MERS lineage responsible for outbreaks in 2015. Coronaviruses (CoVs) are enveloped viruses with a large RNA genome. They are divided into four genera: alpha, beta, gamma, and delta. Beta-CoVs include lineages A, B, C, and D. Lineage A viruses encode a protein similar to the S protein. CoVs infect various animals, including humans, and can cause respiratory and gastrointestinal diseases. Six CoVs infect humans: 229E, OC43, SARS-CoV, NL63, HKU1, and MERS-CoV. These viruses can recombine, leading to new strains. HCoVs are distributed globally, with 229E, OC43, and NL63 prevalent in temperate regions. SARS-CoV caused a severe outbreak in 2002-2003, while MERS-CoV has caused ongoing outbreaks in the Middle East. MERS-CoV is associated with camels and can cause severe respiratory disease. The ecology of HCoVs shows that some are well-adapted to humans, while others are maintained in animal reservoirs. SARS-CoV and MERS-CoV are likely spread through zoonotic reservoirs. SARS-CoV is thought to originate from bats, while MERS-CoV may also originate from bats. Genetic recombination in CoVs is common, leading to new strains. For example, MERS-CoV in camels has recombined to form dominant strains. Recombination events are observed in various CoVs, including SARS-CoV and MERS-CoV. The review highlights the importance of understanding CoV evolution, recombination, and potential for new outbreaks. Future research should focus on monitoring CoV emergence and understanding their transmission dynamics. Lessons from SARS and MERS outbreaks emphasize the need for preparedness against future CoV threats.Since January 2020, Elsevier has created a free COVID-19 resource center with English and Mandarin information on the novel coronavirus. The center is hosted on Elsevier Connect, a public news and information website. Elsevier grants permission to make all its COVID-19-related research immediately available in PubMed Central and other public repositories for unrestricted research use. This review discusses the epidemiology, genetic recombination, and pathogenesis of human coronaviruses (HCoVs). HCoVs include those causing the common cold, SARS, and MERS. Dromedary camels in Saudi Arabia harbor three HCoV species, including a dominant MERS lineage responsible for outbreaks in 2015. Coronaviruses (CoVs) are enveloped viruses with a large RNA genome. They are divided into four genera: alpha, beta, gamma, and delta. Beta-CoVs include lineages A, B, C, and D. Lineage A viruses encode a protein similar to the S protein. CoVs infect various animals, including humans, and can cause respiratory and gastrointestinal diseases. Six CoVs infect humans: 229E, OC43, SARS-CoV, NL63, HKU1, and MERS-CoV. These viruses can recombine, leading to new strains. HCoVs are distributed globally, with 229E, OC43, and NL63 prevalent in temperate regions. SARS-CoV caused a severe outbreak in 2002-2003, while MERS-CoV has caused ongoing outbreaks in the Middle East. MERS-CoV is associated with camels and can cause severe respiratory disease. The ecology of HCoVs shows that some are well-adapted to humans, while others are maintained in animal reservoirs. SARS-CoV and MERS-CoV are likely spread through zoonotic reservoirs. SARS-CoV is thought to originate from bats, while MERS-CoV may also originate from bats. Genetic recombination in CoVs is common, leading to new strains. For example, MERS-CoV in camels has recombined to form dominant strains. Recombination events are observed in various CoVs, including SARS-CoV and MERS-CoV. The review highlights the importance of understanding CoV evolution, recombination, and potential for new outbreaks. Future research should focus on monitoring CoV emergence and understanding their transmission dynamics. Lessons from SARS and MERS outbreaks emphasize the need for preparedness against future CoV threats.