RNA VIRUS PART 2

• Paramyxoviridae


  • Virions are pleomorphic
  • Envelope is fragile and labile to storage conditions
  • Genome is not segmented, thus no frequent gene reassortment (antigenically stable)

  
• All paramyxoviruses are labile to very labile and quickly inactivated, e.g. by heat, organic solvents, detergents, ultraviolet, or visible light, and low pH value

  
• Genera of Paramyxoviridae

  • Paramyxovirus - Parainfluenza viruses and Mumps virus
  • Morbillivirus - Measles virus
  • Pneumovirus - Respiratory syncytial virus

  
• Parainfluenza virus


  Causes mild or severe upper and lower respiratory tract infections, particularly in children
• Parainfluenza virus transmission

  • By droplets or direct contact, disseminates locally in the ciliated epithelial cells of the respiratory mucosa
• Diseases caused by parainfluenza virus

  • Common colds
  • Bronchitis
  • Bronchiolitis
  • Croup
• Parainfluenza virus infections


  • Primary infections occur in young children, reinfection is common but results in milder disease

  
• Parainfluenza virus clinical symptoms

  Non-specific, flu-like, cough, shortness of breath, sometimes fever
• Parainfluenza virus laboratory diagnosis

  • Detecting viral antigen
  • Isolating the virus
  • Detecting a rise in antibody titer or elevated IgG- and IgA- (IgM-) antibodies (serum)
  • RT-PCR

  
• There are no vaccines for parainfluenza virus yet

  
• Mumps virus


  Causes viral parotitis, swelling of the salivary glands, especially the parotid glands
• The single serotype of mumps virus shares antigens with parainfluenza viruses, particularly type 1

  
• Mumps virus transmission

  • Spread in droplets
• Mumps virus incidence

  • Frequently reported in children aged 5-9 years of age, although both adolescents and adults may be affected
• Mumps virus incubation period

  • 2 to 4 weeks
• Mumps virus laboratory diagnosis

  • Isolating the virus in cell culture
  • Detecting viral antigen
  • Detecting specific IgM in the first serum sample soon after onset of symptoms or by a rise of IgG antibodies
• There is supportive treatment for mumps, no specific treatment
• Mumps is prevented by vaccination - Measles (6-9 months), MMR (12-15 months)
• Mumps orchitis


  Pain and swelling of the testicles which normally begins 4-8 days after swelling of the Parotid
• Mumps orchitis


  • Most common complication of mumps in post-pubertal men, affecting about 20%-30% of cases (10%-30% are bilateral)
  • Rarely leads to sterility but it may contribute to subfertility
  • 30%-87% of patients with bilateral mumps orchitis experience infertility
• Mechanism of infertility in mumps orchitis


  Testicular atrophy, low sperm count
• Measles virus

  Morbilli Virus/Rubeola virus, possesses 1 antigenic type
• Measles virus


  • Causes viremia with wide dissemination and multiplies in cells of the lymphatic, respiratory, intestinal and urinary system, the skin, and sometimes the brain
  • Cell-mediated immunity is essential to control of infection, antibody is not sufficient due to measles ability to spread cell to cell
• Measles virus incubation period

  • 8 -12 days
• Measles virus symptoms

  • Coryza, conjunctivitis, fever, and rash
• Measles virus transmission

  • Direct contact with infectious droplets during the prodromal period
• Measles virus period of communicability

  • 4 days before AND 4 days after the onset of the rash
• The typical maculopapular rash appears 1 to 3 days later. Complications include otitis, pneumonia, and encephalitis
• Subacute sclerosing panencephalitis


  A rare late sequela of measles
• Koplik spots

  Grayish white dots with red border opposite the lower molars
• Measles virus laboratory diagnosis

  • Isolating the virus in cell culture by direct smear of cell-containing specimen
  • Detection of RNA with the polymerase chain reaction (RT-PCR)
  • Detecting specific IgM in the first serum at the time of rash with a rising titer of IgG antibodies in the second serum
  • Histopathology - Warthin-Finkeldey giant cells (hyperplastic lymph nodes)

  
• Supportive treatment is provided for measles, no specific treatment
• Measles vaccines


  • Measles vaccine (6 -9 months)
  • Measles/mumps/rubella (MMR) (15 months)

  
• Vitamin A supplement is provided for measles
• Respiratory syncytial virus (RSV)

  Common cause of upper and lower respiratory tract disease in young children
• Respiratory syncytial virus types

  • A
  • B
• RSV transmission


  • By droplets or direct contact, infects the ciliated epithelial cells of the respiratory mucosa and disseminates locally
• RSV disease


  Caused partly by immunopathologic antibody-dependent cellular cytotoxicity
• RSV immunity


  • Nonspecific immune defenses, including interferon, are followed by the appearance of secretory and serum antibody and cell-mediated responses
  • Reinfection occurs, but the frequency and severity of disease decrease with age
• RSV epidemiology


  • Found worldwide; in temperate climates, epidemics occur in winter and early spring and affect mainly infants and young children