ALT Scientific image showing how human coronavirus HKU1 may attach to cells in the nose. On the left, a microscope image shows the virus-binding part of the spike protein attaching to the hair-like surface of ciliated airway cells. On the right, a computer model shows the spike protein leaning toward the cell membrane to reach a sugar-containing molecule called GT3. This supports a possible link between sugar recognition and the virus’s preference for ciliated airway cells.