1 Pathogenic Viruses Name of virus; what family it belongs to; what disease it causes. –DNA or RNA? Ss or ds? –Characteristics of disease, symptoms. –Viral virulence factors Epidemiology: reservoirs, vectors Immunizations

2 Brief review Non-cellular “life forms” –Consists of nucleic acid and capsid (protein) –Some types possess envelope, spikes, accessory proteins Obligate intracellular parasites –Nucleic acid enters host cell, directs operations –Ultimately, new copies of viral N.A., proteins made Virus depends mostly on host cell machinery –Following assembly, new virions escape to infect new hosts

3 Attack and defense Virus has ways of attacking –Specific binding to host cell receptor Receptors involved in normal cell functions –Virus may regulate cell division for its own replication –Insertion of viral DNA into chromosome allows virus to hide from immune system

4 Defense by host Host has ways of defending –Cell mediated immunity (T cells): infected cells killed. –Antibodies intercept virions between cells, in fluids –Interferon produces anti-viral state, prevents replication

5 Our selections for Summer 2005 Herpes Virus family –HSV 1 & 2; VZV; and CMV Hepatitis viruses –Hep A, B, and C: all unrelated, and transmitted differently, but cause similar disease. Mosquito-borne viruses of Arkansas Influenza HIV (possible guest speaker)

6 Herpes virus family Human herpes viruses now numbered –But common names easier to use. As a family: –ability to become latent; –predilection for either nervous tissue or lymphocytes; –ability to cause cancer. Herpes roster: –Herpes simplex, Varicella zoster, cytomegalovirus, Epstein Barr, roseola, Kaposi’s sarcoma virus.

7 Herpes Simplex viruses HHV1 (above the waist) –Typically oral, cold sores; flu-like symptoms, etc. HHV2 (genital), STD and neonatal –Painful, contagious sores on genitals, overlap w/ HHV1. Latency –Viruses enter nearby nerve cells, remain until activated by stress of some sort, cause disease, then return. Spread and treatment: –Person to person by direct contact; spread within host by forming syncytia, escape immune system. –Acyclovir helps; no cure, lifetime infection.

8 Herpes family: Varicella Zoster Varicella: chicken pox; Zoster: shingles –Chickenpox (not a pox virus), respiratory, disease becomes systemic with fever, malaise, skin lesions. –Very contagious; usually mild, esp. in children –Virus can become latent in nerves like Herpes simplex Recurrence: shingles; rash, pain, on one side Acyclovir can lessen symptoms –Beware of salicylates + viruses: Reyes syndrome –Vaccination: Varivax: attenuated vaccine

9 Herpes family: Cytomegalovirus CMV (HHV5): Infection results in enlarged cells –Widespread asymptomatic infections, latency –Virus shed in body fluids: sex, birth, transplants –Problem for unborn, immunosuppressed, transplant patients; major cause of viral-induced birth defects.