Zoonotic viruses replicate in the reservoir animal host and are usually transmitted to human by direct contact or the bite of a hematophagus arthropod.
For example, rabies virus is transmitted by the saliva from a bite of a rabid animal and simian foamy virus can be transmitted by bites from an infected monkey.
Viruses are transmitted either through the mucosal surfaces of the airways, the intestinal or genital tract, or the eye, abrasion of the skin or by directly gaining access to the bloodstream.
Mucosal entry is most common. Viruses, such as influenza viruses, parainfluenza viruses, certain types of adenoviruses or rhinoviruses spread through the airways and are transmitted by droplets at are formed during coughing or sneezing of an infected individual.
Other viruses such a human Papilloma virus (HPV) is spread through sexual contact. HPV may be transmitted through direct contact (oral to genital, oral to oral, skin to skin) although it is typically transmitted through the skin-to-skin route.
Although humans may become ill as a result of the virus, they are generally considered dead-end hosts for many of the viruses because they do not develop sufficient viremia to infect feeding vectors and thus do not contribute to the transmission cycle.
Virus mode of transmission
