Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins

Burton's Microbiology for the Health Sciences Chapter 18. Viral Infections

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 18 Outline Introduction How do Viruses Cause Disease? Infectious Diseases of the Skin Viral Infections of the Ears Viral Infections of the Eyes Viral Infections of the Respiratory System Viral Infections of the Oral Region Viral Infections of the Gastrointestinal Tract Viral Infections of the Genitourinary System Viral Infections of the Circulatory System Viral Infections of the Central Nervous System Recap of Major Viral Infections of Humans Appropriate Therapy for Viral Infections

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins How Do Viruses Cause Disease? Viruses multiply within host cells. It is during their escape from those cells – either by cell lysis or budding – that the host cells are destroyed. This cell destruction leads to most of the symptoms of a viral infection, which vary depending upon the location of the infection.

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Viral Infections of the Skin Chickenpox and Shingles –Varicella-zoster virus (a DNA virus which is also known as human herpesvirus 3) German Measles (Rubella) –Rubella virus, an RNA virus Measles (Hard Measles, Rubeola) –Measles (rubeola) virus, an RNA virus Monkeypox – Monkeypox virus, a DNA virus Smallpox –2 strains of variola virus (variola minor and variola major), a DNA virus Warts –At least 70 different types of human papillomaviruses (HPV), DNA viruses

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Viral Infections of the Eyes Adenoviral conjunctitivis and keratoconjunctivitis – caused by various types of adenoviruses Herpes simplex and varicella-zoster viruses can also cause keratoconjunctivitis. Hemorrhagic conjunctivitis – caused by adenoviruses and enteroviruses People with viral infections (e.g, cold sores) should wash their hands thoroughly before inserting or removing contact lenses or otherwise touching their eyes.

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Viral Infections of the Upper Respiratory Tract The Common Cold (Acute Viral Rhinitis, Acute Coryza) –Many different viruses cause colds. –Rhinoviruses (more than 100 serotypes) are the major cause in adults. –Other cold-causing viruses include coronaviruses, parainfluenza viruses, respiratory syuncytial virus (RSV), influenza viruses, adenoviruses, and enteroviruses. –Transmission occurs via respiratory secretions by way of hands and fomites or direct contact with or inhalation of airborne droplets.

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Viral Infections of the Lower Respiratory Tract Acute, Febrile, Viral Respiratory Disease –Caused by parainfluenza viruses, respiratory syncytial virus (RSV), adenovirus, rhinoviruses, certain coronaviruses, coxsackieviruses, and echoviruses; transmission occurs via direct oral contact or by droplets Avian Influenza (Bird Flu) –Avian influenza virus type A; 3 prominent subtypes – H5, H7, H9; bird to human transmission occurs via contact with infected poultry or contaminated surfaces Hantavirus Pulmonary Syndrome (HPS) –Caused by at least 5 different hantaviruses (Sin Nombre, Bayou, Black Creek Canal, New York-1 Monongahela); transmission occurs via inhalation of aerosolized rodent feces, urine, and saliva

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Viral Infections of the Lower Respiratory Tract, cont. Influenza, Flu –Influenza viruses, types A, B, and C; RNA viruses; transmission is via infected humans; pigs and birds also serve as reservoirs Severe Acute Respiratory Syndrome (SARS) –SARS-associated coronavirus (SARS-CoV) (shown here) –Transmission occurs via infected individuals by respiratory droplets, or by touching the mouth, nose, or eye after touching a contaminated surface or object

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Viral Infections of the Oral Region Cold Sores (Fever Blisters, Herpes Labialis) – Usually caused by herpes simplex virus type 1 (HSV- 1), but can be caused by herpes simplex type 2 (HSV-2) – DNA viruses in the family Herpesviridae – Either HSV-1 or HSV-2 can also infect the genital tract, although genital herpes infections are most often caused by HSV-2

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Cold Sore Caused by Herpes Simplex

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Viral Infections of the GI Tract Viral Gastroenteritis (Viral Enteritis, Viral Diarrhea) –The most common viruses infecting children in their first years of life are enteric adenoviruses, astroviruses, caliciviruses, and rotaviruses. –Viruses infecting children and adults include norovirus-like viruses and rotaviruses. –Transmission occurs via infected humans, most often by way of the fecal-oral route; possibly from contaminated water and shellfish.

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Most Common Types of Viral Hepatitis Type A Hepatitis (HAV Infection, Infectious Hepatitis, Epidemic Hepatitis) –Hepatitis A virus (HAV); a linear ssRNA virus –Fecal-oral transmission Type B Hepatitis (HBV Infection, Serum Hepatitis) –Hepatitis B virus (HBV); an enveloped, circular dsDNA virus –Sexual transmission or household contact with an infected person; injected drug use; tattooing; needlesticks Type C Hepatitis (HCV Infection, Non-A Non-B Hepatitis) –Hepatitis C virus (HCV); an enveloped, linear ssRNA virus –Primarily parenterally transmitted; rarely sexually Type D Hepatitis (HDV Infection, Delta Hepatitis) –Hepatitis D virus (HDV, delta virus); an enveloped, circular ssRNA viral satellite; coinfection with HBV is necessary –Exposure to infected blood and body fluids, etc.

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Most Common Types of Viral Hepatitis, cont. Type E Hepatitis –Hepatitis E virus (HEV); a nonenveloped, ssRNA virus –Fecal-oral transmission; primarily fecally contaminated drinking water; also person-to-person Type G Hepatitis –Hepatitis G virus (HGV); a linear ssRNA virus –Parenteral transmission

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Viral STDs Anogenital Herpes Viral Infections (Genital Herpes) –Usually caused by herpes simplex virus type 2 (HSV- 2); occasionally by HSV-1 –Transmission occurs via infected humans by direct sexual contact; oral-genital, oral-anal, or anal-genital contact when lesions are present Genital Warts (Genital Papillomatosis, Condyloma Acuminatum) –Human papillomaviruses (HPV); DNA viruses –Transmission occurs via infected humans by direct contact, usually sexual –Genital warts can become malignant

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Viral Infections of the Circulatory System Human Immunodeficiency Virus (HIV) Infection, Acquired Immunodeficiency Syndrome (AIDS) –Human immunodeficiency virus (HIV); 2 types - HIV- 1 (most common) and HIV-2; ssRNA viruses –Transmission occurs via infected humans, by direct sexual contact; contaminated needles/syringes; transfusion of contaminated blood; transplacental transfer from mother to child; transplantation of HIV- infected tissues or organs; needlestick, scalpel, and broken glass injuries

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Viral Infections of the Circulatory System, cont. Infectious Mononucleosis( “Mono,” “Kissing Disease”) –Caused by Epstein-Barr virus (EBV), which is also known as human herpesvirus 4; a DNA virus in the family Herpesviridae –Transmission occurs via infected humans, person-to- person, direct contact with saliva Mumps (Infectious Parotitis) –Caused by mumps virus; an RNA virus –Transmission occurs via infected humans by droplet spread and direct contact with saliva

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Viral Hemorrhagic Diseases (Viral Hemorrhagic Fevers) Caused by many different viruses, including dengue virus, yellow fever virus, Crimean-Congo hemorrhagic fever virus, Lassa virus, Ebola virus, and Marburg virus Ebola and Marburg viruses are extremely large filamentous viruses Infected humans serve as reservoirs; infected African green monkeys also serve as reservoirs in Marburg infection Transmission is person-to-person via direct contact with infected blood, secretions, internal organs, or semen; also needlestick

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Viral Infections of the CNS Lymphocytic Choriomeningitis –Caused by lymphocytic choriomeningitis virus (LCMV) –Transmission occurs via exposure to mouse urine, droppings, saliva, or nesting materials Poliomyelitis (Polio, Infantile Paralysis) –Caused by polioviruses; RNA viruses –Transmission is person-to-person, primarily via the fecal-oral route; also throat secretions

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Viral Infections of the CNS, cont. Rabies –Caused by rabies virus; a bullet-shaped, enveloped RNA virus –Many reservoirs, including dogs, foxes, coyotes, wolves, jackals, skunks, raccoons, mongooses, bats –Transmission occurs via the bite of a rabid animal which introduces virus-laden saliva; airborne transmission from bats in caves also occurs Viral Meningitis (Aseptic Meningitis, Abacterial Meningitis) –Caused by many different viruses

Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Selected Arthropodborne Viral Encephalitides of the United States DiseaseReservoirsVectors Eastern Equine Encephalitis (EEE) Birds, horses Aedes, Coquilletidia, Culex, and Culiseta mosquitoes California EncephalitisRodents, rabbits Aedes and Culex mosquitoes LaCrosse EncephalitisChipmunks, squirrelsAedes mosquitoes St. Louis EncephalitisBirdsCulex mosquitoes West Nile Virus Encephalitis Birds, perhaps horsesCulex mosquitoes Western Equine Encephalitis (WEE) Birds, horses Aedes and Culex mosquitoes