1. MENINGOCOCCAL INFECTION Transmission and Disease Brian Greenwood London School of Hygiene & Tropical Medicine

2. THE PATHWAY OF INFECTION Pharyngeal carrier Respiratory droplets (meningococci) Susceptible host Pharyngeal carrier CASE

3. Carrier Droplets CASE 199 1 THE CYCLE OF INFECTION

4. THE PATHWAY OF INFECTION Pharyngeal carrier Respiratory droplets (meningococci) Susceptible host Pharyngeal carrier CASE 1 2 3 4

5. THE PATHWAY OF INFECTION Pharyngeal carrier Respiratory droplets (meningococci) Susceptible host Pharyngeal carrier CASE 1

6. INFECTIOUSNESS OF A CARRIER Density of carriage Duration of carriage Respiratory infection Durationof carriage % ? importance

7. THE PATHWAY OF INFECTION Pharyngeal carrier Respiratory droplets (meningococci) Susceptible host Pharyngeal carrier CASE 2

8. SURVIVAL OF MENINGOCOCCI IN RESPIRATORY DROPLETS Droplet size Environmental temperature Environmental humidity

9. HUMIDITY AND BACTERIAL SURVIVAL 20 30 40 50 60 70 80 90 100 Towns Villages Relative humidity (%) Concentration of airborne bacteria (Ghipponi et al. Bull WHO 1971; 45:95)

10. THE PATHWAY OF INFECTION Pharyngeal carrier Respiratory droplets (meningococci) Susceptible host Pharyngeal carrier CASE 3

11. COLONISATION OF THE MUCOSA Cilia Epithelial cells Numbers of meningococci Integrity of the mucosa Physical damage Microbiological damage LOCAL IMMUNE DEFENSES

12. THE PATHWAY OF INFECTION Pharyngeal carrier Respiratory droplets (meningococci) Susceptible host Pharyngeal carrier CASE 4

13. Integrity of the mucosa Local immune defenses INVASION Mucosa Capillary

14. Carrier Droplets CASE 190 10 CHANGING THE CARRIER TO CASE RATION

15. SURVIVAL IN THE HOST HOST IMMUNITY Natural exposure Passive protection Vaccination Host genetics Environmental factors

16. 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

17. 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.