The present invention provides the complete genomic sequence of a novel human coronavirus, coined as coronavirus-HKU1 ("CoV-HKU1"), isolated in Hong Kong from a patient who had a recent history of visit to Schenzhen, China. The virus belongs to the order Nidovirales of the family Coronaviridae, being a single-stranded RNA virus of positive polarity. The invention also provides the deduced amino acid sequences of the complete genome of the CoV-HKU1. The nucleotide sequences and deduced amino acid sequences of the CoV-HKU1 are useful in preventing, diagnosing and/or treating the infection by CoV-HKU1. Furthermore, the invention provides immunogenic and vaccine preparations using recombinant and chimeric forms as well as subunits of the CoV-HKU1 based on the nucleotide sequences and deduced amino acid sequences of the CoV-HKU1.