24. Epidemiology and prevention of airborne bacterial infections

From greek.doctor

Airborne infections:

  • Inhalation of organisms suspended in the air on water droplets or dust particles
  • Prevention:
    • Handwashing
    • Keep distance from sick people
    • Sick people should keep distance from healthy people
    • Vaccines

Bacterial airborne infections:

  • Tuberculosis
  • Diphtheria
  • Pertussis
  • Neisseria meningitidis (meningococcus)
  • Haemophilus influenzae
  • Streptococcus pneumoniae (pneumococcus)
  • Legionnaire disease

Tuberculosis

  • Mycobacterium tuberculosis hominis/bovis
  • Epidemiology
    • 9th leading cause of death worldwide
    • 27 000 new cases every day
    • Leading cause of death in HIV-positive
    • Incidence and mortality dropping in the last 20 years
    • Globally the incidence decreases by 2% each year
    • 95% of TB-related deaths occur in low- and middle-income countries
    • Incidence of multidrug and extensively drug resistant TB increases
  • Risk factors for severe TB
    • HIV (or other immune suppression)
    • Severe disease (DM, renal failure)
    • TNF alpha inhibitors
  • TB is most prevalent among
    • Migrants
    • Homeless
    • Poor people
    • Drug abusers
  • Treatment
    • Childhood TB is generally treatable
    • Adult TB is less treatable
  • Prevention
    • Isolation of TB patients
    • Disinfection by UV light or tuberculocidial disinfectants
    • Special air filters
    • Routine TB testing for high-risks
  • BCG vaccine
    • Live attenuated Mycobacterium bovis
    • Unchanged since 1921
    • Only 50% effective against TB
    • Good protection against childhood TB meningitis and miliary TB
    • Poor protection against adult pulmonary TB
    • Intradermal injection in the deltoid
      • If given subcutaneously -> can form abscess

Diphtheria

  • Corynebacterium diphtheriae
  • Epidemiology
    • Global reported cases down since vaccine was introduced in the 80s
    • Very rare in countries with high coverage with vaccine
  • Clinical features
    • Short incubation period
    • Produces pseudomembrane in the pharynx
      • Makes breathing and swallowing difficult
    • Produces diphtheria toxin
      • Myocarditis
      • Peripheral neuropathy
      • Nephritis
  • Vaccine
    • Toxoid vaccine – toxin is inactivated with formalin
    • DTaP vaccine at 3, 5 and 12 months, 7, 15 years (in Norway) + booster (Tdap) every 10 years
    • Vaccine lasts 10 years
    • Intramuscular vaccine
    • Because vaccine doesn’t protect against the infection itself, only the (toxin-mediated) disease, there is no herd immunity!

Pertussis

  • Bordetella pertussis
  • Epidemiology
    • Important cause of infant death worldwide
    • It’s a public health concern even in countries with high vaccination coverage
  • Produces pertussis toxin
  • Clinical features
    • Whooping cough – paroxysmal coughing
    • Pneumonia
    • Apnoea
  • Vaccine
    • Acellular pertussis (DTaP)
    • Given at 3, 5 and 12 months, 7, 15 years (in Norway) + booster (Tdap) every 10 years

Streptococcus pneumoniae (pneumococcus)

  • Epidemiology
    • Often in fall, winter
  • Clinical features
    • Common cause of community-acquired pneumonia, bacterial meningitis
    • Bacteraemia
    • Otitis media
  • Colonizes nasopharynx
  • Vaccine
    • Conjugate vaccine
    • Given at 3, 5 and 12 months

Haemophilus influenzae

  • Colonizes nasopharynx
  • Causes otitis media, meningitis, epiglottitis, sinusitis
  • Vaccine
    • Conjugate vaccine
    • Only for H. flu type b – the only type with a capsule and therefore only pathogenic type
    • 3, 5 and 12 months

Legionellosis

  • Legionella pneumophila
  • Epidemiology
    • Mostly affects older males
  • Risk factors
    • Smoking
    • Lung disease
    • Recent intubation
  • Inhalation of contaminated aerosol
  • Two forms
    • Non-pneumonic form – causes Pontiac disease (influenza-like illness)
    • Pneumonic form – causes Legionnaire disease – severe pneumonia
      • -> respiratory failure -> death in 5%
  • No vaccine available

Neisseria meningitidis

  • Epidemiology
    • Mostly occurs in sub-Saharan Africa
    • Epidemics during winter, spring
    • Serotype B and C account for most cases in western world
    • Serotype A accounts for most cases in Africa
  • No animal reservoir – only human
  • Clinical features
    • Lethality 10% when treated, 50% when untreated
    • Mainly affects children and infants
    • Causes bacterial meningitis
    • Asymptomatically colonizes nasopharynx in 10 – 30% of healthy
  • Vaccine
    • Polysaccharide vaccine used during outbreaks
    • Conjugate vaccine used for prevention
  • Chemoprophylaxis
    • Antibiotic prophylaxis for people in close contact to infected