brain function
Figure 21.5 Viruses are classified based on their core genetic material and capsid design. a Rabies virus has a single-stranded RNA ssRNA core and an enveloped helical capsid, whereas b variola virus, the causative agent of smallpox, has a double-stranded DNA dsDNA core and a complex capsid. Rabies transmission occurs when saliva from an infected mammal enters a wound. The virus travels through neurons in the peripheral nervous system to the central nervous system where it impairs brain function, and then travels to other tissues. The virus can infect any mammal, and most die within weeks of infection. Smallpox is a human virus transmitted by inhalation of the variola virus, localized in the skin, mouth, and throat, which causes a characteristic rash. Before its eradication in 1979, infection resulted in a 3035 percent mortality rate. credit rabies diagram: modification of work by CDC; rabies micrograph: modification of work by Dr. Fred Murphy, CDC; credit small pox micrograph: modification of work by Dr. Fred Murphy, Sylvia Whitfield, CDC; credit smallpox photo: modification of work by CDC; scale-bar data from Matt Russell .