Final answer:
Genetic changes such as antigenic drift and antigenic shift, and vectors like mosquitoes and ticks, are biological factors that can significantly affect the spread of viral pathogens.
Step-by-step explanation:
Biological Factors Affecting the Spread of a Virus Pathogen
Two important biological factors that affect the spread of a virus pathogen are genetics and vectors.
Genetics
Viruses undergo genetic changes through processes such as antigenic drift and antigenic shift. Antigenic drift involves small, gradual changes that occur as the virus replicates. This can modify the virus's surface proteins and lead to seasonal flu outbreaks. Antigenic shift, on the other hand, is a more sudden and significant change that can occur when two different strains of a virus merge. This can lead to the creation of a new, highly virulent strain against which people have little to no immunity, potentially causing pandemics.
Vectors
Vectors are organisms that transmit pathogens between hosts. Common vectors for viral diseases include mosquitoes, ticks, and flies. These vectors can either mechanically transmit the virus, by carrying it on their body, or biologically, where the virus reproduces inside the vector before being transmitted to a new host. An infected vector can thus spread the virus more widely and rapidly across populations.