virus — a small infectious agent that can only replicate inside living cells

a scientist peers into a microscope while tiny spherical organisms with spiky surfaces float around cellular structures. The small round agents attach themselves to larger healthy cells in the petri dish. Once attached, the cells begin changing color and multiplying the infectious agents inside them. Another scientist points at the microscope screen showing the replication process in action. The organisms spread from cell to cell, creating more copies of themselves. small infectious agents that can only replicate inside living cells