Virusurile sunt agenți patogeni microscopici care nu au o structură celulară și nu pot supraviețui sau reproduce independent. Ele sunt considerate entități la granița dintre lumea vie și cea nevie, deoarece au nevoie de o celulă gazdă pentru a se multiplica.
-Simple Structure: They consist of genetic material (DNA or RNA) surrounded by a protein coat called a capsid. Some viruses also have an external membrane, called an envelope.
-Obligate Intracellular Parasite: They cannot perform vital functions (such as metabolism or reproduction) without infecting a host cell.
-Extremely Small Size: Usually, they range from 20 to 300 nanometers, making them much smaller than bacteria.
Various Shapes: They can be spherical, helical, complex, or icosahedral.