In the quiet margins of European gardens and Asian fields, hedgehogs carry a family of coronaviruses related to the deadly MERS pathogen — and scientists at Washington State University have now traced the precise biological key these viruses use to enter living cells. The discovery, published in Nature Microbiology, reveals that while humans are not currently vulnerable, cats, rats, and other animals share a cellular receptor that could welcome these pathogens across species lines. It is a reminder that viral evolution is not an event but a process, unfolding slowly through each animal encount