Coronaviruses have long been known as important pathogens in the veterinary field that can cause severe diseases in livestock and companion animals. In humans, however, coronaviruses have essentially been neglected for a long time since they were known to cause mainly mild respiratory symptoms (common cold), except for rare cases in elderly and immune-compromised people. This changed dramatically when SARS emerged. In 2002, a new zoonotic coronavirus emerged causing severe acute respiratory syndrome (SARS) in humans. Up to this date only two human coronaviruses were known, namely HCoV-229E and HCoV-OC43. But in the aftermath of the SARS-CoV outbreak two new human coronaviruses, HCoV-NL63 and HCoV-HKU1, were identified, and surprisingly they have already been for long time in the human population but have not been discovered until researchers specifically looked for coronaviruses. In 2012 the sixth human coronavirus, Middle East respiratory syndrome (MERS-)CoV, emerged in the Arabian Peninsula, and like SARS-CoV, MERS-CoV can cause severe respiratory disease in humans. Interestingly, the phenomenon of emerging coronaviruses has also been observed in the veterinary field, for example in pigs with the recent emergence of the high pathogenic swine acute diarrhea syndrome (SADS-)CoV.