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MENINGOCOCCAL INFECTION
Transmission and Disease
Brian Greenwood
London School of Hygiene & Tropical Medicine
THE PATHWAY OF INFECTION
Pharyngeal carrier
Respiratory droplets (meningococci)
Susceptible host
Pharyngeal carrier
CASE
Carrier
Carrier
Droplets Droplets
CASE
199
1
THE CYCLE OF INFECTION
THE PATHWAY OF INFECTION
Pharyngeal carrier
Respiratory droplets (meningococci)
Susceptible host
Pharyngeal carrier
CASE
1
2
34
THE PATHWAY OF INFECTION
Pharyngeal carrier
Respiratory droplets (meningococci)
Susceptible host
Pharyngeal carrier
CASE
1
INFECTIOUSNESS OF A CARRIER
• Density of carriage
• Duration of carriage
• Respiratory infection
Durationof carriage
% ? importance
THE PATHWAY OF INFECTION
Pharyngeal carrier
Respiratory droplets (meningococci)
Susceptible host
Pharyngeal carrier
CASE
2
SURVIVAL OF MENINGOCOCCI IN RESPIRATORY DROPLETS
• Droplet size
• Environmental temperature
• Environmental humidity
HUMIDITY AND BACTERIAL SURVIVAL
20 30 40 50 60 70 80 90 100
TownsVillages
Relative humidity (%)
Con
cen
trat
i on
of
air b
orn
e b
acte
ria
(Ghipponi et al. Bull WHO 1971; 45:95)
THE PATHWAY OF INFECTION
Pharyngeal carrier
Respiratory droplets (meningococci)
Susceptible host
Pharyngeal carrier
CASE
3
COLONISATION OF THE MUCOSA
Cilia
Epithelial cells
Numbers ofmeningococci
Integrity of the mucosa
Physicaldamage
Microbiologicaldamage
LOCAL IMMUNE DEFENSES
THE PATHWAY OF INFECTION
Pharyngeal carrier
Respiratory droplets (meningococci)
Susceptible host
Pharyngeal carrier
CASE
4
Integrity ofthe mucosa
Local immunedefenses
INVASION
Mucosa
Capillary
Carrier
Carrier
Droplets Droplets
CASE
190
10
CHANGING THE CARRIER TO CASE RATION
SURVIVAL IN THE HOST
HOST IMMUNITY
Natural exposure
Passive protection
Vaccination
Hostgenetics
Environmentalfactors
Pharyngeal carrier
Respiratory droplets (meningococci)
Susceptible host
Pharyngeal carrier
Case
IMPACT OF THE ENVIRONMENT
Survival of meningococci in droplets
Damage to mucosa facilitating colonisation
Damage to mucosa facilitating invasion
Influence on the immune response
TOPICS FOR FUTURE RESEARCH
• The impact of environmental factors on meningococcal survival in droplets.
• The impact of environmental factors on mucosal immune defences.
• The influence of the environment on the Immune response to vaccination.