English: Intrinsic and extrinsic factors that can make viruses unsuccessful during their life cycle stages. Host specificity refers to the attachment and insertion of genetic material (DNA or RNA) into the hosts, latent period refers to the duration of the viral infection within the host during which virus particles are produced, burst size refers to the number of viral progeny released and particle state refers to the state where viruses are not within a host. Extrinsic factors are divided into host resistance mechanisms, abiotic and biotic stressors, and they can affect viruses during any of their life stages.