Viruses

Viruses

1. RNA based

   • Naked
     • Icosahedral
       • + ssRNA nonsegmented
         • Picornaviridae
           • Enteroviruses
             • Polio, coxsackie, echovirus, enterovirus 70, Hepatitis A
               • All are stable around pH 3-9. Replicate at 37 degrees celsius and use ICAM-1 cell surface receptors. Peak during summer and fall. Humans only host.
             • Rhinovirus
               • Labile at pH 3. Prefers 33-35 degrees celcius, in the nasal mucosa. Uses ICAM-1 receptors and peak during winter and spring
         • Caliciviridae
           • Norwalk virus
         • Hepeviridae
       • dsRNA segmented
         • Reoviridae
           • Rotavirus
           • Coltivirus
             • Replication
               • Enters cell by endocytosis. Capsid is partially removed from genome in endolysosome but never fully exposed in order to prevent activation of antiviral state.
             • Pathogenesis
               • Infects erythroid precursor cells without damaging them and replicates in bone marrow, heart, lungs, lymph nodes, and spleen. This way the virus remains in the mature cells and is protected from the host. On the other hand, infection of cells of the small vessels will cause hemorrhaging
             • Vector/reservoir
               • Vector is the wood tick  and reservoir is the golden mantled ground squirrel.
             • Disease
               • Colorado tick fever
   • Enveloped
     • ssRNA, nonsegmented
       • Capsid Shape
         • Helical Nucleocapsid
           • Coronaviridae
         • Icosahedral nucleocapsid
           • Flaviridae
             • Diseases
               • Encephalitis
                 • Fever, stiff neck, vomiting, headache
                 • West Nile Virus
                   • For differential, exclude HSV-1
                 • St. Louis
                 • Powassan
               • Dengue Fever
                 • Caused by Dengue virus. Low grade fever for 1-3 days, headaches, Eye, bone, and muscle pain as well as itchy rash. Dengue hemmorhagic fever is due to the second serotype of virus and can lead to a sever complication called dengue shock syndrome
                 • Similarity to Chickunguya
                   • Both virus are transmitted by the same mosquito and show similar clinical symptoms and since they circulate around the same area, can co-infect. However, dengue fever is more likely to cause neutropenia and thrombocytopenia while chinkungaya is more likely to cause lymphopenia. Important to rule out dengue because proper management of dengue can improve symptoms
               • Yellow fever
                 • Caused by yellow fever virus. Hemmorhagic fever with high fatality- usually in about 5 days. Causes degeneration of the liver with jaundice. Causes kidney, heart, and GI damage Treatment: vaccine available. also control of vector
               • Hepatitis C Virus
             • Diagnoses/Prevention
               • Look for IgM and IgG bodies. Mosquito control is the best prevention
           • Togaviridae
             • Rubella Virus
             • Alpha virus
               • Causes encephalitis and is arthropod borne. Has a bird mosquito life cycle which is important and can expand to horses and humans which are dead end hosts. Lytic infection in bird and persistent in mesquitos
               • Syndromes
                 • Encephalitis
                   • Found in North and South America, carribeans
                 • Fever with arthritis, myalgia, and rash
                   • Found in Asia and Africa with the Aedes mesquito as vector and the Chikungya strain of the virus
               • Pathogenesis
                 • Bite causes primary viremia (FLU), then spreads to capillary endothelial cells, macrophages, monocytes, and RE cells causing RASH. Secondary viremia follows next and can cause damage to the brain, muscles, and joints. However, if antibodies are present, secondary viremia does not occur.
               • Diagnosis
                 • Diagnose serologically by looking for IgM or IgG. usually a 4-fold rise in the antibodies is diagnostic
     • Diploid ssRNA, nonsegmented
       • Capsid shape
         • Complex nucleocapsid
           • Retroviridae
             • Spumaretrovirinae
               • Spuma virus
                 • Animal and human diseases
             • Orthoretrovirinae
               • animal pathogens
                 • Alpha, beta, gama, epsilon retrovirus
               • Human and animal pathogens
                 • HTLV (deltaretrovirus) and HIV (Lentivirus)
     • -ssRNA
       • Segmented
         • orthomyxoviridae
         • Bunyaviridae
         • Arenaviridae
       • Nonsegmented
         • Paramyxoviridae
         • Rhabdoviridae
         • Filoviridae
         • Deltavirus
           • Hepatitis Virus D

2. DNA based

   • Icosahedral & Naked
     • ssDNA
       • Parvoviridae
         • Replication process
           • Virus replication: Requires mitotically active cells Prefers erythroid precursor cells= anemia Attaches to erythrocyte P antigen
         • Parvovirus B19
     • dsDNA
       • Papilomaviridae, Polyomaviriae, Adenoviridae
   • Enveloped
     • Icosahedral enveloped
       • DS DNA
         • Herpesviridae
           • All cause latent infections reactivated by environmental and host factors
           • HSV-1, 2
           • VZV
           • EBV
           • CMV
           • HHV-6,7,8
         • Hepadnaviridae
           • Hepatitis B Virus
     • Complex enveloped
       • DS DNA
         • Poxviridae
           • Replication process
             • 1) Cellular enzymes come and remove outer membrane 2) Early transcription uncoating enzyme 3) uncoating enzyme unwraps genome 4) delayed early transcripts produce DNA polymerase 5) Virions released via cellular villi
           • Molluscum Contagiosum, small pox, vaccinia