Final answer:
Virus particles find the 'right' cell by attaching to specific receptor sites on the cell surface.
Step-by-step explanation:
Virus particles find the 'right' cell by attaching to specific receptor sites on the cell surface. This attachment is mediated by attachment proteins in the capsid or glycoproteins embedded in the viral envelope. The interaction between the viral attachment proteins and the cell receptor determines the host species and specific cell types that can be infected by the virus.
For example, the virus that causes human influenza (flu) binds specifically to receptors on the membranes of cells in the respiratory system. These receptors are unique to humans and cannot be recognized by the virus in other species, such as chickens.
Overall, the specificity of attachment is essential for viruses to successfully enter the host cell, replicate, and spread to other cells or individuals.