Pathogenic Viruses

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Pathogenic Viruses

• Name of virus
• what family it belongs to
• what disease it causes, organ system affected
• DNA or RNA?
• Route of transmission reservoirs, vectors
• Viral virulence factors (selected viruses)
• Immunizations

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Herpes virus family

• Herpes family of DNA viruses
• As a family, infects epithelial cells, lymph
  cells, and/or nerve cells.
• Associated with latent infections and cancer
• Spread by direct contact, fluid exchange
• Herpes simplex 1 (cold sores) and 2 (STD)
• Drug treatment acyclovir and related drugs
• Cannot be cured

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Herpes continued

• Varicella zoster chickenpox reactivation of
  latent state shingles
• Varivax vaccine protects
• Drugs limit severity, duration of shingles
• Epstein Bar virus mononucleosis
• Infection of B cells and salivary glands
• Sore throat, fatigue, brittle spleen
• Cytomegalovirus CMV
• Common, subclinical infection
• Severe problem with AIDS, transplants, and cause
  of birth defects

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Common cold viruses

• Rhinovirus (picornavirus, small RNA virus)
• Most common
• Coronavirus (RNA virus)
• Related to virus that causes SARS
• Sudden acute respiratory distress syndrome
• Adenovirus (DNA virus)
• Some strains cause GI distress instead
• Parainfluenza virus (RNA)
• Related to flu and measles
• Spread by various forms of contact.

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Parainfluenza family (RNA)

• Rubeola (measles)
• Highly contagious, possible serious complications
• Systemic infection, red rash
• US immunized with MMR vaccine under control
• Mumps virus
• Infects parotid glands, many other glands
• Deafness most serious complication
• US immunized with MMR vaccine under control
• Parainfluenza virus
• Mild respiratory infection, cold symptoms

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Parainfluenza family continued

• Respiratory syncytial virus (RSV)
• Host young children, can be fatal in infants
• Cold symptoms in older individuals
• Virus spreads in host by forming syncytia
• NOT a parainfluenza virus but similar spread and
  symptoms German Measles (Rubeola)
• Due to birth defects, women of child-bearing age
  should have immunity.
• US immunized with MMR vaccine under control

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Viruses of the GI tract

• All RNA viruses (either ss or ds)
• Enterovirus
• Picornavirus family, includes polio, Hepatitis A
• Norovirus
• Rotavirus
• Spread by fecal-oral route of transmission cause
  of outbreaks in daycares, restaurants, cruise
  ships, etc. vomiting and diarrhea.

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Animal associated viruses

• Rhabdovirus cause of rabies
• Infects brain and salivary glands
• Animals spread virus in saliva by biting
• Slow acting, can be immunized against after
• Nearly always fatal unless treated.
• Arboviruses
• Unrelated viruses spread primarily by mosquitoes
• Affect other creatures (horses, birds) as well as
  humans
• Locally important ones cause encephalitis

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continued

• St. Louis encephalitis
• Eastern Equine encephalitis
• Kills people and horses
• West Nile virus
• Generally mild in people, but kills certain birds
• Other arboviruses (e.g. Dengue fever) more of a
  tropical problem, but if global warming
  continues, becomes OUR problem. Endemic in Mexico.

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Fungi

• Systemic infections
• Generally acquired by inhalation of spores
• Lung infections, may spread beyond into other
  tissues
• Histoplasma (histoplasmosis)
• Most common in this area (Ohio and Miss. River
  valleys)
• Soil contaminated with bird or bat droppings
• Many people exposed with asymptomatic cases

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Opportunists

• Aspergillus (aspergillosis)
• Variety of species, very common in soil, plant
  materials
• Serious infections in immunocompromised
• Poisoning from aflatoxin from A. flavus
• Cryptococcus neoformans
• Inhalation of spores, has predilection for CNS
• Particularly serious in AIDS
• Pneumocystis carinii
• Very protozoan like, but is a fungus
• Most cases associated with AIDS
• Serious lung infections PCP (P. carinii
  pneumonia)

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Protozoans

• Eukaryotic single-celled organisms
• Eukaryotic means harder to treat infections
• Group responsible for human diseases are the
  animal-like protozoa.
• Protozoa are widespread in nature, most not
  pathogenic
• Protozoa typically have life cycles
• Simple, like vegetative cell and cyst
  (spore-like) Amoebas
• Complex, like sporozoans have

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Protozoal diarrheas

• Cryptosporidium
• Primarily livestock and poultry, acquired
  fecal-oral through food or contaminated water.
• Diarrhea, but systemic spread as well, highly
  dangerous to AIDS patients.
• Giardia lamblia
• Hikers diarrhea, from many water sources
• Common cause of diarrhea 1-4 weeks.

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Other problem protozoal diseases

• Trypanosoma various species, geographic
  locations
• Cause of African sleeping sickness, spread by
  bite of tsetse fly Infection of CNS, causes
  coma
• Cause of Chagas disease, spread by bite of
  reduviid bug eventually damages heart tissue.
• Leishmania
• Causes leishmaniasis, spread by sandfly (see
  Gulf war)
• Various levels of severity of systemic disease
• Toxoplasma toxoplasmosis
• kills fetus many organs in immune compromised .
• Part of life cycle involves cats, so pregnant
  women must stay away from litter box.