Coronaviruses can be quite promiscuous with their genes. If two or more strains infect the same cell, then mixing (homologous recombination) can occur, creating a chimera. This diagram shows two parental viruses at the top, both contribute to the chimeric daughter virus at bottom centre. The daughter has inherited the genes for the spike protein from the red parent. This is one possible origin of SARS2, the novel coronavirus.