MICROPARA (WEEK 9- CANVAS)

• Viruses


  Obligatory intracellular parasites, viral genes carried in the genomes of other organisms provide a record of viral evolution

  
• Viruses


  • Contain only one form of nucleic acid, either DNA or RNA
  • Contain a protein coat that covers the nucleic acid (which is sometimes surrounded by an envelope of lipids, proteins, and carbohydrates)
  • Multiply inside living cells by utilizing the cell's synthesis mechanism
  • Cause the formation of specialized structures capable of transferring viral nucleic acid to other cells
• Hosts infected by viruses

  • Invertebrates
  • Vertebrates
  • Plants
  • Protists
  • Fungi
  • Bacteria
• Viral size


  The tiniest viruses have a diameter of around 20 nm, whereas influenza and the human immunodeficiency virus have a more usual size of about 100 nm. Human cells have a diameter of 10–30 m (microns), which implies they are 100–1000 times larger than the viruses that infect them
• Viral classification


  • Classified by their nucleic acid and by differences in the structures of their coats
  • Viral genes are encoded by either DNA or RNA—but never both
  • The genome of a virus can be single-stranded or double-stranded. Depending on the virus, the nucleic acid can be linear or circular. In some viruses (such as the influenza virus), the nucleic acid is in several separate segments
• Viral structure


  • Capsid and Envelope
  • Capsids come in about three different shapes: icosahedral, prolate, and helical
  • Each capsid is composed of protein subunits called capsomeres
  • Helical viruses are made up of a single type of capsomer that is stacked around a central axis to produce a helical structure with a central cavity or hollow tube
  • The icosahedral virus is made up of identical subunits that form equilateral triangles that are then stacked symmetrically
  • Prolate - An isosahedron extended along one axis, which is a common arrangement of bacteriophage heads
  • Envelope – Some viruses have an extra layer outside of their capsule called an envelope. Another name for the envelope is membrane. They may help viruses avoid the host immune system
  • Complex viruses contain capsids that are neither entirely helical nor purely icosahedral, and they may include additional structures like protein tails or a complex outer wall
• Exanthem


  Any eruptive cutaneous rash accompanied by fever and other systemic symptoms. It is caused by a drug reaction, a disease, or both. Most children's exanthems are viral infections.
• Skin viral infections associated with maculopapular exanthem

  • Measles (Hard Measles, Rubeola)
  • German Measles (Rubella)
  • Roseola Infantum (Exanthem Subitum or Sixth Disease)
  • Erythema Infectiosum
• Skin viral infections associated with vesicular exanthem

  • Chickenpox
  • Herpes Zoster (Shingles)
  • Smallpox (Variola)
  • Warts
  • Herpes Simplex virus
  • Hand-foot-mouth Disease
• Measles (Hard Measles, Rubeola) is a common, highly contagious childhood exanthem associated with serious complications. The pathogen is the measles virus (also known as rubeola virus), an RNA virus in the family Paramyxoviridae.
• German Measles (Rubella) is a mild, febrile viral disease caused by the rubella virus.
• Roseola Infantum (Exanthem Subitum or Sixth Disease) is caused by Human Herpes virus 6 and manifests as sudden onset of high-grade fever followed by a generalized rash that lasts for two days.
• Erythema Infectiosum (also known as fifth disease) is a common childhood infection caused by human parvovirus B19, causing a slapped cheek appearance and a rash.
• Chickenpox is an acute, generalized viral infection caused by the varicella-zoster virus (VZV), with fever and a skin rash. Vesicles also form in mucous membranes; it can be severely damaging to a fetus and has serious complications including pneumonia, secondary bacterial infections, hemorrhagic complications, and encephalitis.
• Herpes Zoster (Shingles) is a reactivation of the varicella virus, resulting from immunosuppression, involving inflammation of sensory ganglia of cutaneous sensory nerves, producing fluid-filled blisters, pain, and paresthesia (numbness & tingling).
• Smallpox (Variola) is a systemic viral infection caused by 2 strains of variola virus: variola minor (fatality rate of 1%), and variola major, with symptoms including fever, malaise, headache, prostration, severe backache, and a distinctive skin rash.
• Warts are skin and mucous membrane lesions caused by at least 70 types of human papillomaviruses (HPV), classified in the genus Papillomavirus within the family Papovaviridae.
• Herpes Simplex virus causes infections of the skin and mucous membranes, is capable of latency and recurrent infections, and results in watery blisters on the skin or mucous membranes.
• Hand-foot-mouth disease is a viral infection.
• Warts


  Common warts (verrucae vulgaris), venereal warts, and plantar warts are among the many types of skin and mucous membrane lesions

  
• Most warts are harmless, but some can become cancerous
• Pathogens causing warts


  At least 70 types of human papillomaviruses (HPV), classified in the genus Papillomavirus within the family Papovaviridae
• Types of skin warts

  • Common, plantar and flat warts
  • Genital and anogenital warts

  
• Herpes Simplex virus


  Causes infections of the skin and mucous membranes, capable of latency and recurrent infections
• Herpes Simplex virus symptoms

  • Watery blisters on the skin or mucous membranes of the mouth, lips, nose, or genitals
• Clinical findings of Herpes Simplex virus

  • Gingivostomatitis
  • Herpes labialis
  • Herpetc whitlow
  • Eczema herpeticum
  • Herpes gladiatorum
• Hand-foot-mouth Disease (HFMD)


  A mild, contagious viral infection common in young children
• Pathogens causing HFMD


  • Most commonly caused by a coxsackievirus A16, but coxsackievirus A6 and enterovirus 71 (EV-A71) can also cause it
• HFMD symptoms


  • Fever, body aches, sores in the mouth and a rash on the hands and feet
• HFMD transmission


  • Spreads from person to person by direct contact with nasal discharge, saliva, and fluid from the rash of an infected person, contact with contaminated surfaces & objects
• HFMD treatment


  • Symptomatic treatment is given to provide relief from fever, aches and pains
• HFMD prognosis


  • Usually a mild illness but contagious with the rash healing in 5-7 days
• HFMD infectious period


  • Remains while there is fluid in the blisters, and feces also remain infectious for several weeks after the onset of illness
• Cold Sores (Fever Blisters, Herpes Labialis)


  Superficial clear vesicles on an erythematous (reddened) base, may appear on the face or lips, crust and heal within a few days
• Causes of Cold Sores


  • Reactivation may be caused by trauma, fever, physiologic changes, or disease
• Pathogens causing Cold Sores

  Usually caused by herpes simplex virus type 1 (HSV-1), although they can also be caused by herpes simplex virus type2 (HSV-2)
• Adenoviral Conjunctivitis and Keratoconjunctivitis

  Acute viral infections that causes inflammation of the conjunctiva, edema of the eyelid & periorbital tissue, pain, photophobia, and blurred vision
• Pathogens causing Adenoviral Conjunctivitis and Keratoconjunctivitis


  • Caused by various types of adenoviruses, herpes simplex and varicella-zoster viruses can also cause keratoconjunctivitis
• Hemorrhagic Conjunctivitis


  With sudden onset, with redness, swelling, and pain in one or both eyes, small, discrete subconjunctival hemorrhages may enlarge to form confluent subconjunctival hemorrhages
• Pathogens causing Hemorrhagic Conjunctivitis

  • Enterovirus 70 and Coxsackie A24 virus