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Clinical Virology: Part Two The Viruses

Clinical Virology: Part Two The Viruses. MLAB 2434 – Microbiology Keri Brophy-Martinez. Respiratory Viruses. Influenza Viruses ssRNA virus Causes crucial health problems epidemics and pandemics Antigenic drifts and shifts Major or minor changes in viral surface glycoproteins

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Clinical Virology: Part Two The Viruses

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  1. Clinical Virology: Part TwoThe Viruses MLAB 2434 – Microbiology Keri Brophy-Martinez

  2. Respiratory Viruses • Influenza Viruses • ssRNA virus • Causes crucial health problems • epidemics and pandemics • Antigenic drifts and shifts • Major or minor changes in viral surface glycoproteins • Attack ciliated epithelial cells of respiratory tract

  3. Respiratory Viruses(cont’d) • Parainfluenzae Viruses • Enveloped RNA • Major cause of respiratory disease in young children • Respiratory Syncytial Virus (RSV) • Enveloped RNA • Most common virus isolated from infants with LRT infections • Spread by contact with respiratory secretions

  4. Respiratory Viruses(cont’d) • Adenoviruses • Half of all infections are asymptomatic • Causes 10% of all pneumonia cases • Causes 5% - 15% of all gastroenteritis in children • dsDNA, nonenveloped

  5. Respiratory Viruses (cont’d) • Rhinoviruses • Major cause of common cold • Infect nasal epithelial cells and activate inflammatory response • ssRNA, small and naked • No cure • Coronaviruses • ssRNA • Cold-like infections

  6. Exanthemas • Definition = skin eruption accompanying certain infectious diseases • Mumps • ssRNA • Swelling of parotid glands, testes, ovaries and pancreas • Vaccine available

  7. Exanthemas (cont’d) • Measles (Rubeola) • ssRNA virus • Abrupt onset with sneezing, runny nose and cough, red eyes and high fever, followed by maculopapular (flat discolored area of skin with raised bump) rash on head and trunk • Also see Koplik’s spots- bright red spots with white centers • Easily diagnosed clinically; lab requests rare

  8. Exanthemas (cont’d) • Rubella • Enveloped ssRNA • Mild febrile illness with rash and lymphadenopathy; many cases asymptomatic • Rash starts on face and spreads to trunk and limbs; no rash on palms and soles • Causes birth defects in first trimester • Vaccine strongly recommended • Serologic titer for immune status

  9. Exanthemas (cont’d) • Parovirus B19 • ssRNA • Causes Erythema Infectiosum, also known as “Fifth Disease” • “Slapped cheek” appearance, spreading to trunk and limbs

  10. Immunodeficiency Viruses • Human Immunodeficiency Virus Type 1 • AIDS • ssRNA • Target cells are CD4+ T cells • Destruction of these cells results in opportunistic infections

  11. Central Nervous System Viruses • Enteroviruses • ssRNA virus • Includes poliovirus, coxsackie A and B, and echovirus • Transmission: Fecal-oral/respiratory • Causes a variety of infections and conditions, including paralysis • Resistant to disinfectants

  12. Agents of Gastrointestinal Infections • Known to cause the “stomach flu” • Includes adenovirus, norovirus, rotavirus • Rotaviruses • dsRNA with double-layer protein capsid • Most common cause of gastroenteritis in infants, children • Oral-fecal route • Hand washing and vaccines for prevention

  13. Agents of Gastrointestinal Infections (cont’d) • Norovirus • Originally called Norwalk and Norwalk-Like Agents • Gastroenteritis in older children and adults • Outbreaks in camps, schools, and on cruise ships • Nausea, vomiting, diarrhea and low-grade fever • Highly infectious

  14. Family Arenaviridae • Causes hemorrhagic fevers • Lassa Fever • Transmitted by rodents • Acquired by aerosol or skin abrasion

  15. Family Filoviridae • Includes Ebola and Marburg viruses • Human infections may result from contact with infected monkeys • High mortality rates • Unknown reservoirs in nature

  16. Rabies • Transmitted by bite or scratch from infected animal • Pain at site of infection, followed by flu-like symptoms • CNS system changes, followed by death • Vaccine and postexposure prophylaxis available • Detected in brain of source animal

  17. Human Papilloma Virus • dsDNA virus • Causes • Leading cause of sexually transmitted disease • Common and plantar warts • Genital warts • Associated with cervical cancers

  18. Hepatitis Viruses • Hepatitis A (HAV) • oral-fecal • Person-person contact, contaminated food/water • RNA • Anti-HAV antibodies emerge around 10 days

  19. Hepatitis Viruses • Hepatitis B (HBV) • Blood and body fluids • DNA • Hardy organism

  20. Hepatitis Viruses • Hepatitis C (HCV) • Blood and body fluids • RNA • For diagnosis- Anti-HCV serology • Hepatitis D (HDV) • Blood and body fluids • RNA • Requires HBV for replication • Hepatitis E (HEV) • Oral-fecal • RNA

  21. Herpesviruses • HSV Type 1 • Oral herpes • “Cold sores” • Can cause encephalitis • Recurrent • HSV Type 2 • Genital herpes • Neonatal herpes • Can cause encephalitis • Recurrent

  22. Herpesviruses (cont’d) • Varicella-zoster • Varicella causes chicken pox • Zoster is clinical manifestation of reactivated varicella virus, which can be latent in nerve tissue (“Shingles”) • Epstein-Barr • Mononucleosis • Associated with Burkitt’s lymphoma, nasopharyngeal carcinoma, Hodgkins lymphoma

  23. Herpesviruses (cont’d) • Cytomegalovirus (CMV) • Most common congenital infection in U.S. • Most adults have antibodies to CMV • Herpesvirus 6 • Causes Roseola Infantum or “Sixth Disease”

  24. Herpesviruses (cont’d) • Herpsevirus 7 • Infects CD4 + cells • Viruses present in 75% of adult saliva • Herpsevirus 8 • Detected in Kaposi’s sarcoma • Not culturable

  25. Arboviruses • Derive name from mode of transmission (arthropod born) • Humans are dead-end hosts • Families • Bunyaviridae family • Vector- mosquito • Hemorrhagic fever, including Hanta virus • Encephalitis

  26. Arboviruses (cont’d) • Togaviridae family • Encephalitis • Reoviridae family • Colorado tick fever • Flaviviridae family • Most common cause of arboviral encephalitis in the world, including St. Louis encephalitis (SLE) • West Nile • Dengue fever (Classic and hemorrhagic) • Yellow fever

  27. Antiviral Therapy • Like bacteria and antibiotics, the use of antivirals can result in virus resistance • Some viral infections are treatable, especially if therapy is given early in infection • Antivirals must be designed to target a viral replication mechanism without destroying host cells • Vaccinations

  28. References • Kiser, K. M., Payne, W. C., & Taff, T. A. (2011). Clinical Laboratory Microbiology: A Practical Approach . Upper Saddle River, NJ: Pearson Education. • Mahon, C. R., Lehman, D. C., & Manuselis, G. (2011). Textbook of Diagnostic Microbiology (4th ed.). Maryland Heights, MO: Saunders. • http://www.fifthdisease.org/general.html • http://www.idph.state.il.us/about/immunepics/measles.htm • http://www.idph.state.il.us/about/immunepics/mumps.htm • http://www.mc3cb.com/viruses.html

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