Rabdovirus

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Rabdovirus

• The virion is from Rabdoviridea family.
• Morphology nucleocapside is like a bullet
• Genome linear single stranded RNA, Negative
  sense, M protein, RNA-dependent RNA polymerase,
  Enveloped.

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Disease Rabies

• Several hosts including all warm-blooded living
  things, especially in dog, wolf, fox, bat.
• Human to human transmission is very rare.
• The virus can be found in nerve system, saliva,
  urine, lymph, milk.
• There is only one serotype of rabies virus.
• Glycoprotein G is a main cause of virus invading
  to nerve system.

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Pathogenesis

• Virus amplification in muscles ? nerve - muscle
  synapses ? virus entering into peripheral nerves
  ? central nerve system ? Attachment to
  Asetylcholin ? entering to the brain and
  multiplication ? progressive encephalitis ? virus
  moving to saliva glands and other organs like
  pancreas, kidney, heart, retina, cornea, through
  peripheral nerves.

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Clinical findings

• Incubation period 20 days to 2 months (but seen
  between 1 week to 19 years) depends to the age,
  genetic background, race, the number of virus
  inoculated, the distance of virus to central
  nerve system.
• Rabies is an accidental viral infection in human.

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• Clinical periods includes 3 stages
• I. Introductory short stage
• 2-10 days non-specific symptoms (headache,
  photophobia, nausea, vomiting, sore throat,
  fever, no appetite.
• II.2-7 days partial paralysis, cerebral
  dysfunction, anxiety, sleeplessness, confusion,
  agitation, abnormal behavior, terror,
  hallucinations. Increased activity of simpatico
  system such as increased tear secretion,
  increased saliva, hydrophobia.
• III. Coma and death

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Lab diagnosis

• Negri bodies in brain or spinal cord (spherical,
  2-10 microns granules. They contain rabies
  antigens and detectable by immunoflorosence (IF)
  methods.
• Virus isolation in humestesr or mice cells.
• PCR
• Serologic methods (Detecting antibodies)

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Prevention and treatment

• All infected animals should be killed and their
  tissues should be tested in lab.
• Vaccination (inactivated virus) is used for
  people who have been bitted or their job is known
  as high risk carrier.
• Antibody (antiserum) prophylaxis.
• No treatment

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Common cold viruses

• Rinoviruses
• Adenoviruses
• Coronaviruses
• Enteroviruses
• Parainfluenza viruses
• Influenza viruses

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Rinoviruses

• The main cause of the common cold
• From Picornaviruses
• RNA single strand, sense, The genome includes a
  small viral Pr at 5 end.
• No envelope
• Ichozahedral
• 28-30 nm (as a small virus)

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Important properties

• More than 100 serological types
• Replicate better at 33C than 37C (affecting
  primarily nose and conjunctiva rather than the
  lower respiratory tract).
• Acid-labile, so killed by gastric acid when
  swallowed.
• The host range humans and chimpanzees

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Pathogenesis

• Entering through the upper respiratory tract
• There is a correlation between the concentration
  of viruses in nasal dischargse (or mucosa) and
  the severity of disease.
• The viruses are usually seen in 2-4 days after
  infection.
• Some times virus still is detectable by 3 weeks.

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• The virus spread is limited to the epithelial
  surface of nasal mucosa.
• Histopathology changes are limited to the surface
  of epithelium and includes Edema and low
  penetration of cells.
• Cold weather does not cause common cold or even
  not increase the chance for it.

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Clinical finding

• Incubation period 2-4 days
• Acute stage sometimes to 7 days but dried cough
  can last by 2-3 weeks.
• Adults 1-2 cold onset per year.
• Symptoms sneeze. sore throat. chill, some times
  low fever, nasal congestion and loss of smell.

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Clinical finding

• There is no way to distinguish common cold
  caused by rinoviruses from common colds by others
  viruses.
• Bacterial secondary infection otitis, sinusitis,
  bronchitis, pneumonia.

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Immunity

• Antibody appearance is late 7-21 days after
  infection appearance in noise and serum at the
  same time.
• Antibody may clear virus from the body finally.

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Epidemiolohy and Transmission

• Worldwide
• More often is in early autumn and late spring and
  minimum in summer
• Transmission through fingers or shared things is
  more important than aerosol droplets.
• Family and school are two source of contamination
  for children.

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Treatment and prevention

• No spesific treatment
• No high chance for a vaccine production
• The culture for high concentration of virus is
  difficult.
• 2. The immunity is short.
• 3. The serotypes are very high.

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Adenoviruses

• Double-stranded linear DNA, icosahedral
  nucleocapsid (80-90 nm).
• The only viruses with a fiber protruding from
  each of the 12 vertices.
• The fiber is the organ of attachment and is a
  hemagglutinin.
• There are more than 40 known antigenic types and
  the fiber protein is the main type-specific
  antigen.

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Diseases

• Upper respiratory tract infections Pharyngitis,
  pharyngoconjunctivitis.
• Conjunctivitis
• Pneumon
• Keratoconjunctivitis
• Hemorrhagic cystitis
• Gastroenteritis
• Latent infections particularly in the adenoidal
  and tonsillar tissues.

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Clinical findings of adenovirus infection

• Varying degrees of fever, sore throat, coryza,
  and conjunctivitis.
• In the lower respiratory tract, atypical
  pneumonia is characterized primarily by fever and
  cough.

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Lab diagnosis

• Isolation of the virus in cell culture
• Detection of 4-fold rise in antibody titer.
• Serological tests Hemagglutination test

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Treatment and prevention

• Most adenovirus infections resolve
  spontaneously.
• No antiviral therapy
• An enteric-coated capsule vaccine is used only
  in military recruits in USA but not available for
  civilian use.

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The Influenza Parainfluenza viruses
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Orthomyxoviridae Paramyxoviridae
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Classification
Family
Genus
Types
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• myxo refers to interaction with mucins
  (glycoproteins)
• Different from paramyxoviruses - segmented
  genome
• - smaller (average 110 nm in diameter against 150
  nm).

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An enveloped viruse, helical symmetry capsid,
segmented linear RNA genome
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Surface glycoproteins

• Haemagglutinin
• H or HA
• responsible for pathogenicity of the virus
• allows virus to adhere to endothelial cells in
  the respiratory tract
• main determinant of immunity
• Neuraminidase
• N or NA
• allows release of newly formed viruses within
  host
• determinant of disease severity

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Antibody against the hemagglutinin neutralizes
the infectivity of the virus and prevents
disease. Ab against neuraminidase only reduces
disease.
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Influenza subgroups

• Influenza A
• highly infective
• infects many species
• causes widespread epidemics
• Influenza B
• found only in humans
• capable of producing severe disease
• causes regional epidemics
• Influenza C
• causes mild disease
• humans are natural hosts, but isolates also found
  in pigs
• does not cause epidemics

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• Reassortment of segments of the genome RNA
• Influenza viruses, especially type A show changes
  in the antigenicity of their hemagglutinin and
  neuraminidase proteins. ? epidemics.
• Influenza viruses antigenes
• Group-specific (internal ribonucleoprotein)
  antigenes.
• Type-specific (surface N and H) antigens.

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Many species of animal (eg. Birds, swine, and
hourses) have their own influenza A
viruses. These animal viruses are probably the
source of the new antigenic types. Antigenic
shift Major changes based on reassortment of
genome pieces. Occurs every 10-11 years
Antigenic drift Minor changes based on mutation
occurs every year.
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• Antigenic shift appears to result from genetic
  recombination of human with animal or bird
  ,providing major antigenic change.This can cause
  a major epidemic or pandemic involving most or
  all age groups.

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Epidemics and pandemics occur when the
antigenicity of the virus has changed
sufficiently that the preexisting immunity of
many people is no longer effective.
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• Various combinations of RNA segments can result
  in a new subtype of virus (known as antigenic
  shift
• It is even possible to include RNA strands from
  birds, swine, and human influenza viruses into
  one virus if a cell becomes infected with all
  three types of influenza.

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Occurrence of influenza A viruses

• Influenza A viruses 16 HA types
• 9 NA types
• Species affected humans, pigs, horses,
  birds, marine mammals
• In humans 3 HA types (H1, H2, H3)
• 3 NA types (N1, N2, N8)
• In birds all HA types
• all NA types

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Influenza viruses nomenclature
For example
A / Beijing / 32 / 92 (H3N2)
A virus type, here A
Beijing place where the strain was isolated
32 strain number
92 year of first isolation
H3N2 subtypes H3 and N2 virus sub type, here
H3N2
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ELECTRON MICROSOPE IMAGE OF H1N1 INFLUENZA VIRUS
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Pathogenesis
After the virus is inhaled, the neuraminidase
degrades the protective mucus layer, allowing the
virus to gain access to the cells of the upper
and lower respiratory tract. Viremia rarely
occurs, but there is necrosis of the superficial
layers of respiratory epithelium.
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Immunity Circulating IgG against the virus occurs
after infection, but offers little protection.
Secretory IgA in the respiratory tract is
protective.
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SYMPTOMS OF SWINE FLU IN HUMANS
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• Clinical findings
• Incubation period 24-48 hours
• Symptoms fever, myalgias, headache, cough
  develop suddenly.
• The symptoms resolve spontaneously in 4-7 days
  but sometimes is complicated with secondary
  infections.
• Reys syndrome (Encephalopathy and liver
  degeneration life-threatening complication in
  children) following some viral infections,
  particularly influenza B and chikenpox, if they
  have been given Asprin to reduce the fever.

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COMPLICATIONS

• Pneumonia
• Respiratory failure
• Convulsion (muscles contract and relax rapidly
  and repeatedly, resulting in an uncontrolled
  shaking of the body)

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When to Seek Emergency Medical Care

• has difficulty breathing or chest pain
• has purple or blue discoloration of the lips
• is vomiting and unable to keep liquids down
• has signs of dehydration such as dizziness when
  standing, absence of urination, or in infants, a
  lack of tears when they cry
• has seizures (for example, uncontrolled
  convulsions)
• is less responsive than normal

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RISK GROUPS

• Persons with certain chronic medical condition
• School children
• Travelers to some high risk places
• Border workers
• Health care workers or public health workers

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PREVENTION

• Prevention in swine or other animal hosts.
• Prevention of transmission to humans.
• Prevention of its spread among humans.

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Prevention of its spread among humans.

• Frequent washing of hands with soap and water

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• Use of face masks

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• Use of
• towel while sneezing

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• Use of alcohol based sanitisers.

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Lab diagnosis

• Virus isolation (by throat washing) with cell
  culture. Then flurescent-antibody staining of the
  infected cells by using antisera to influenza A
  and B.
• A rise in antibody titer of at least 4-fold in
  serum samples using hemmagglutination inhibition
  or complement fixation.
• PCR reactions

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TREATMENT

• supportive care is required.
• Antibiotics (to treat this disease, do help
  prevent bacterial pneumonia and other secondary
  infections.)
• Viral agent is used in severe infections.
• (Zanamivir is recommended by C.D.C.)

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SWINE INFLUENZA
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WHAT IS SWINE INFLUENZA?

• Swine flu is a respiratory disease caused by
  influenza viruses that infect the respiratory
  tract of pigs.
• Swine flu produces most of the same symptoms in
  pigs as human flu produces in people.

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HISTORY OF SWINE INFLUENZA

• The 1918 flu pandemic in humans was associated
  with H1N1 and influenza appearing in pigs, this
  may reflect a zoonosis either from swine to
  humans, or from humans to swine.

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• Since the isolation of virus in 1933 major
  antigenic change have occurred twice (1957-H2N2)
  and again in (1968-H3N3)
• Strains occuring between 1946 and 1957 have been
  called H1N1 strains.

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VACCINE

• The current trivalent influenza vaccine is
  likely to provide protection against the new 2009
  H1N1 strain.

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TREATMENT

• supportive care is required.
• Antibiotics (to treat this disease, do help
  prevent bacterial pneumonia and other secondary
  infections.)
• Zanamivir is recommended by C.D.C.

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IN HUMANS

• Bed Rest
• Keep the sick person in a room separate from the
  common areas of the house.
• The U.S. Centers for Disease Controland
  Prevention recommends the use of Tamiflu
  (oseltamivir or Relenza (zanamivir) for the
  treatment and/or prevention of infection with
  swine influenza viruses.