Viruses and Prions

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Viruses and Prions
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RNA Viruses
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Picornaviruses

• Poliomyelitis
• Fecal-oral and pharyngeal transmission
• Attacks NS and can cause paralysis
• Vaccine has nearly eradicated the disease in US.
• Hepatitis A
• Fecal oral transmission, often through
  contaminated food
• Enteroviruses cause a variety of diseases
  including, febrile illnesses, and acute
  hemorrhagic conjunctivitis, GI diseases
• Rhinoviruses- common colds

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Viruses that cause GI diseases

• Rotaviruses (Reoviridae)
• Caliciviruses
• Norwalk virus
• Norwalk-like viruses

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Coronavirus

• SARS (Severe acute respiratory syndrome
• first reported in Asia in February 2003.
• In 2003, a total of 8,098 people worldwide became
  sick with SARS of these, 774 died
• High fever, headache, myalgia, dry cough,
  pneumonia
• Spread by close contact
• Common cold viruses

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Bunyaviruses

• Hantavirus Pulmonary Syndrome (HPS)
• Rodents are reservoir
• Virus airborne from rodent feces
• Viral encephalitis
• Crimean Congo Hemorrhagic Fever (CCHF)
• Vector borne zoonosis

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Togaviruses

• Rubella (German measels)-produces flat pink rash
• usually mild, but congenital rubella syndrome
  can cause sever abnormalities in babies
• Arboviral Encephalitis viruses -Equine
  encephalitis
• EEE (most severe)
• WEE
• VEE

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Orthomyxoviruses Influenza

• A variety of types (A, B, and C) infect many
  birds and mammals
• Type A can infect humans and cause pandemics
• Transmembrane proteins Hemagglutinin and
  Neuraminidase mediate viral attachment and entry
• Mutations cause antigenic drift which results in
  frequent changes of HA
• Genetic reassortments between different Influenza
  viruses result in antigenic shift

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Pandemic Strain
Antigenic shifts
Avian viruses
Antigenic shifts
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Paramyxoviruses

• Respiratory Syncitial Virus
• Children under 1 most severely affected
• Common, mild in adults
• Mumps- swellings of oral cavity
• Measels (rubeolla)- produces raised red rash
• Parainfluenza-croup

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Arboviral flaviviruses

• West Nile Fever
• Emerging disease in US
• Relatively mild
• Infects many birds and mammals
• Culex spp. are vectors
• St. Louis encephalitis (SLE)
• Yellow fever- monkeys are reservoir
• Dengue fever and DHF (breakbone fever)

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Hepatitis C virus

• Flaviviridae family
• Hepacivirus genus
• Causes liver disease and cancer
• Transmitted through blood, IV drugs, body
  piercing, tattoos

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Rabies Virus

• Transmitted by bite of infected mammals
• Virus migrates from PNS to CNS
• Inclusion bodies (Negri bodies) found in brain
  tissue
• IFAT of brain tissue
• Infects most mammals, susceptibility varies and
  is correlated with maintenance
• Slow incubation allows for post-infection
  vaccination

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HIV human Immunodeficiency Virus (Retroviridae)

• Viral properties
• Envelope
• Protein coat
• Complex RNA genome
• RT and integrase enzymes
• Infection, dissemination through lymphoid organs,
  clinical latency, expression of HIV, clinical
  disease, and death
• Progressive antigenic variation in response to
  hosts immune system
• CD4 T cell depletion leads to immunodeficiency

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DNA viruses
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Herpesviruses

• Herpesviridae contains several important agents
  of human disease and NOT all of them are sexually
  transmitted
• HSV-1 and HSV-2
• Varicella-Zoster
• Epstein-Barr virus (EBV)

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Herpes simplex viruses

• HSV-1 fever blisters
• HSV-2 genital herpes
• Both viruses can cause either symptoms
• Permanent infections, remain latent in spinal
  nerves and erupt into lesions at original site of
  infection
• Lesions are progressively less severe

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Chicken pox and Shinglesvericella-zoster virus

• Chicken pox (vericella)
• virus enters through mucus membranes
• Skin lesions appear after 2 weeks starting on
  scalp and trunk and moving to other epithelial
  sites including respiratory, digestive tract or
  vagina
• Remain in spinal nerves for decades
• Shingles (zoster)- eruption of latent virus from
  peripheral nerves to dermatomes

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Pox viruses

• Small pox (variola virus)-
• Enters throat and resp. tract
• Infects phagcytic cells and blood cells
• Pus-filled vesicles form in mouth and throat then
  face, forearms, hands
• Cow pox (vaccinia), monkeypox viruses-
• less severe than small pox
• antibodies cross reactive with small pox
• Molluscum Contagiosum Virus-
• causes painless pearly white tumors
• increasing as an STD can can become inflamed
  around genitals

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Warts (Papillomas)Papovaviridae

• HPV- human papilloma viruses
• Transmitted by direct contact or fomites
• Many different types that can infect a variety of
  locations including skin, genital, respiratory
  tracts
• Virus infection lasts a lifetime
• Can be malignant
• Cervical cancer-99 of cases linked to HPV
• Warts may be most problematic in
  immunocompromised
• Warts not always present

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Hepatitis B virus

• Hepadnaviridae
• One of the most common blood borne pathogens
• Causes liver diseases and cancer
• Transmitted through blood and sex
• Vertical transmission from mother to baby

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Prion Diseases

• Mad Cow Disease (BSE)
• Scrapie
• vCJD
• Kuru

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Prions
Infectious proteins Normally found on surface of
mammalian cells Abnormal secondary and tertiary
structures Resistant to heat and radiation Long
incubation period
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Prion replication
Normal protein transformed from helices to beta
pleated sheets
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BSE