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Respiratory Viruses

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Respiratory Viruses Respiratory diseases occur most frequently in colder weather, especially in raining season, and in cases of overcrowding. Causes of sever viral ... – PowerPoint PPT presentation

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Title: Respiratory Viruses


1
Respiratory Viruses Respiratory diseases occur
most frequently in colder weather, especially in
raining season, and in cases of overcrowding.
Causes of sever viral respiratory illnesses in
developing countries include measles virus,
influenza and parainfluenza viruses, and
respiratory syncytial viruse.
2
  • 1- Measles virus
  • Measles virus belongs to the family
    Paramyxovirus.
  • VIRUS
  • It is a single stranded RNA spherical particle
  • with helical capsid symmetry.
  • It is surrounded by an envelope.
  • The virus can be grown in human and animal tissue
    culture cells.

3
  • Transmission and pathogenecity
  • In developing countries measles is a serious and
    fetal disease in non immune young children,
    especially with malnutrition and immune
    suppressive children.
  • The virus is highly infectious and spread mainly
    by air droplets.
  • Clinical features
  • Early clinical features include, fever, cough,
    nasal discharge and
    conjunctivitis followed by a rash.
  • Complications which develop due to sever measles
    and ,or, secondary bacterial or viral infection
    include bronchopneumonia and diarrhea,
    conjunctivitis which may lead to ulcerative
    keratitis and blindness. Anaemia often develops.

4
  • Prevention
  • Usually by immunization with live vaccine at 9
    months old.
  • Great caring must be taken when dealing with
    measles samples.
  • An efficient cold storage must be used.
  • Lab diagnosis
  • Measles usually diagnosed clinically. If
    laboratory assist is required, it is recommended
    to take nasopharyngeal specimen and use the
    immunofluorescence technique.

5
  • 2. Influenza Virus
  • RNA virus.
  • belong to the family Orthomyxovirus
  • enveloped virus
  • 3 types A, B, and C
  • Type A undergoes antigenic shift and drift.
  • Type B undergoes antigenic drift only
  • and type C is relatively stable

6
  • Clinical features
  • The clinical features of influenza "flu" include
    fever, chills, tiredness, headache, muscle pain,
    sore throat. Infection is by inhaling the virus.
  • Severe case can lead to influenza pneumonia which
    can be fetal.
  • Influenza A Virus
  • Usually causes a mild febrile illness.
  • Death may result from complications such as
    viral/bacterial pneumonia.

7
Past Antigenic Shifts
  • 1918 H1N1 Spanish Influenza 20-40 million
    deaths
  • 1957 H2N2 Asian Flu 1-2 million deaths
  • 1968 H3N2 Hong Kong Flu 700,000 deaths
  • 1977 H1N1 Re-emergence No pandemic
  • At least 15 HA subtypes and 9 NA subtypes occur
    in nature. Up until 1997, only viruses of H1, H2,
    and H3 are known to infect and cause disease in
    humans.

8
  • Avian Influenza
  • H5N1
  • An outbreak of Avian Influenza H5N1 occurred in
  • Hong Kong in 1997 where 18 persons were infected
    of which 6 died.
  • The source of the virus was probably from
    infected chickens and the outbreak was eventually
    controlled by a mass slaughter of chickens in the
    territory.
  • However, the strains involved were highly
    virulent for their natural avian hosts.
  • H9N2
  • Several cases of human infection with avian H9N2
    virus occurred in Hong Kong and Southern China in
    1999.
  • The disease was mild and all patients made a
    complete recovery
  • Again, there was no evidence of reassortment

9
  • Laboratory Diagnosis
  • This is required at the start of a new epidemic
    so that the virus type and subtype can be
    identified and, if needed a new vaccine is
    prepared.
  • Detection of Antigen - a rapid diagnosis can be
    made by the detection of influenza antigen from
    nasopharyngeal aspirates and throat washings by
    IFT and ELISA
  • Virus Isolation - virus may be readily isolated
    from nasopharyngeal aspirates and throat swabs by
    egg inoculation and cultural technique.

10
  • Prevention
  • Inactivated vaccines are available against
    influenza A and B.
  • The vaccine is normally trivalent, consisting of
    one A H3N2 strain, one A H1N1 strain, and one B
    strain.
  • The strains used are reviewed by the WHO each
    year.
  • The vaccine should be given to debilitated and
    elderly individuals who are at risk of severe
    influenza infection.
  • If however, an epidemic is caused by a new
    subtype, previous immunization is ineffective.

11
  • 3- Parainfluenza Virus
  • ssRNA virus
  • belonging to the family Paramyxoviruse
  • enveloped, pleomorphic morphology
  • 5 serotypes 1, 2, 3, 4a and 4b
  • Closely related to Mumps virus

12
  • Transmission and pathogenicity
  • Parainfluenza viruses are highly infectious but
    about 30-50 of infections are without symptoms.
  • The most serious Parainfluenza viral infections
    occur in young children. The exudate produced by
    the inflamed cells of the respiratory tract can
    cause obstruction of the larynx and bronchi
    (Croup).
  • Type 1 and 2 Parainfluenza viruses are often the
    cause of croup, and infections tend to occur as
    epidemics.
  • Parainfluenza type 3 is a major cause of sever
    bronchiolitis and bronchopneumonia in infants.
  • Type 4 is of low pathogenicity
  • Vaccines against Parainfluenza viruses are not
    yet available.

13
  • Clinical Manifestations
  • Croup (laryngotracheobroncitis) - most common
    manifestation of parainfluenza virus infection.
    However other viruses may induce croup e.g.
    influenza and RSV.
  • Other conditions that may be caused by
    parainfluenza viruses include Bronchiolitis,
    Pneumonia.
  • Management
  • No specific antiviral chemotherapy available.
  • Severe cases of croup should be admitted to
    hospital and placed in oxygen tents.
  • No vaccine is available.

14
  • Laboratory Diagnosis
  • Detection of Antigen - a rapid diagnosis can be
    made by the detection of parainfluenza antigen
    from nasopharyngeal aspirates and throat
    washings.
  • Virus Isolation - virus may be readily isolated
    from nasopharyngeal aspirates and throat swabs.
  • Serology - a retrospective diagnosis may be made
    by serology.

15
  • 4- Respiratory Syncytial Virus (RSV)
  • ssRNA virus.
  • belong to the Paramyxovirus family.
  • Causes a sizable epidemic each year.
  • It is surrounded by an envelop.
  • RSV can be grown in tissue culture.
  • Infected cells joined together in masses called
    syncytia.
  • Inclusion bodies can be present.

16
  • Transmission and pathology
  • RSV is a cause of sever and occasionally fetal
    bronchiolitis and pneumonia in infants.
  • It can also cause infections of the upper
    respiratory tract.
  • A complication of RSV in young children is otitis
    media.
  • RSV is highly infectious. It is spread from one
    person to person mainly by droplet infection
  • No vaccine against RSV is available at present.
  • Breast feeding provides some protection for
    infants.
  • responsible for 50-90 of Bronchiolitis and 5-40
    of Bronchopneumonia
  • Other manifestations include croup (10 of all
    cases).

17
  • Infants at Risk of Severe Infection
  • Infants with congenital heart disease - infants
    who were hospitalized within the first few days
    of life with congenital disease are particularly
    at risk.
  • Infants with underlying pulmonary disease -
    infants with underlying pulmonary disease,
    especially bronchopulmonary dysplasia, are at
    risk of developing prolonged infection with RSV.
  • Immunocompromized infants
  • children who are immunosuppressed
  • or have a congenital immunodeficiency
  • disease may develop lower respiratory
  • tract disease at any age.

18
  • Laboratory Diagnosis
  • Detection of Antigen - a rapid diagnosis can be
    made by the detection of RSV antigen from
    nasopharyngeal aspirates.
  • Virus Isolation - virus may be readily isolated
    from nasopharyngeal aspirates. However, this will
    take several days.
  • Serology

19
Respiratory Viruses
Features Envelop Nuclic acid Family Virus
virus can be grown in human and animal tissue Enveloped helical RNA Paramyxovirus Measles
3 types A, B, and C Enveloped helical RNA Orthomyxovirus Influenza
5 serotypes 1, 2, 3, 4a and 4b Closely related to Mumps virus Enveloped helical RNA Paramyxovirus Parainfluenza
Causes a sizable epidemic each year. can be grown in tissue culture. Inclusion bodies can be present. Enveloped helical RNA Paramyxovirus Respiratory Syncytial (RSV)
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