25. Epidemiology and prevention of airborne viral infections

From greek.doctor

Airborne viral infections

  • Influenza
  • Measles
  • Mumps
  • Rubella
  • Varicella zoster
  • Parainfluenza
  • Varicella
  • Epstein Barr virus

Measles

  • Measles virus, a paramyxovirus
    • Also called morbillivirus
  • Highly contagious, serious disease
    • Contagiosity index 95-99%
  • Epidemiology
    • Used to be a leading cause of infant death, blindness and disability
    • Most commonly affects children < 12 months
    • Vaccination caused an 80% drop in cases from 2000 to 2017
      • During this time 21 million deaths have been prevented
      • This has made the measles vaccine one of the best buys in public health
    • Recently, measles has begun to bounce back
      • Because of anti-vaxxers (pro-diseasers)
  • Spread by coughing and sneezing
  • Clinical features
    • 1-3 deaths per 1000 in developed countries
    • 150 deaths per 1000 in developing countries
      • Due to these children being malnourished and having worse immunity
    • Maculopapular rash
    • Blindness
    • Severe diarrhoea
    • Otitis media (due to bacterial superinfection)
    • Pneumonia (due to bacterial superinfection)
    • Encephalitis
    • Subacute sclerosing panencephalitis
  • No specific treatment
  • MMR vaccine

Rubella

  • Rubella virus, a togavirus
  • Epidemiology
    • 100 000 are born with congenital rubella syndrome every year
  • Clinical features
    • Generally mild illness
    • Part of TORCH (congenital rubella syndrome)
      • Serious for pregnant women
      • Causes deafness, blindness, in infants
  • No specific treatment
  • MMR vaccine

Influenza

  • Type A and B exists – type A is most pathogenic
  • Very hard to vaccinate against – antigens change constantly
    • Antigenic drift – point mutations in the Haemagglutinin (H) and neuraminidase (N) genes
    • Antigenic shift – two different strains combine to form a new strain with different surface antigens
  • Pandemics in history
    • Spanish flu (1918)
    • Asian flu (1957)
    • Hong Kong flu (1968)
    • Swine flu (2009)
  • Seasonal epidemics during winter
  • Can cause severe illness in high risk populations
    • Small children
    • Elderly
    • Pregnant women
    • Chronically ill
  • Vaccination
    • Contains killed virus
    • Recommended for at-risk populations
      • Healthcare workers
      • Children up to 5
      • Elderly
      • Pregnant
      • COPD
    • The serotype of the influenza virus changes all the time -> WHO must try to predict which serotype will cause epidemic every year and produce vaccine against that type
    • For every year the vaccine is taken the more efficient it becomes
  • Preventative measures
    • Hand hygiene
    • Covering mouth and nose when sneezing, use tissues
    • Self-isolation when symptoms occur
    • Avoid close contact with sick people

Mumps

  • Mumps virus
  • Clinical features
    • Meningitis
    • Pancreatitis
    • Encephalitis
    • Orchitis – male infertility
  • MMR vaccine