Cholera. Cholera prevention and control. Mode of Transmission. Ganges River Delta. Public health significance

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1 * This presentation is prepared by the author in one s personal capacity for the purpose of academic exchange and does not represent the views of his/her organisations on the topic discussed. Cholera prevention and control Are we ready to combat a cholera epidemic? Journal Club/ Grand Round Meeting in Administrative Medicine Dr Teresa Choi 27 September 2003 Dr Teresa Choi 1 Cholera Clinical presentation acute onset profuse watery diarrhoea without significant abdominal pain nor fever Caused by: Vibrio cholerae Pathogenesis: Cholera toxin causing massive secretion of fluid and electrolytes into bowel causing dehydration and electrolyte disturbances Dr Teresa Choi 2 V. cholerae of public health importance Typing system Serogroups Biotypes for V.cholerae O1 Serotypes for V.cholerae O1 Toxin production Epidemic associated O1, O139 Classical, El Tor Ogawa, Inaba, Hikojima Produce cholera toxin Non-epidemic associated Non-O1 Not applicable Not applicable Usually do not produce cholera toxin Dr Teresa Choi 3 Mode of Transmission Faecal-oral route contaminated food, e.g. raw or undercooked seafood, shellfish contaminated water Direct contact Person-to-person Dr Teresa Choi 4 Public health significance Ganges River Delta V.cholerae O1 Classical biotype caused 6 pandemics between 1817 and th pandemic started in 1961 and still ongoing, caused by V.cholerae O1 El Tor biotype V.cholerae O139 as another epidemic associated strain identified in 1992 Dr Teresa Choi 5 Dr Teresa Choi 6

2 Global Cholera Situation Dr Teresa Choi 7 WHO Dr Teresa Choi 8 Distribution of cholera cases Cholera in the past 10 years Hong Kong Dr Teresa Choi 9 Dr Teresa Choi 10 Cholera control Safeguard against pathogen introduction Environmental measures to stop sustained transmission Remove source of infection Border Control International health regulations Hong Kong Law Port Health (Department of Health) Dr Teresa Choi 11 Dr Teresa Choi 12

3 Schedule 1 infectious diseases (Cap 141) 1. Acute poliomyelitis 2. Amoebic dysentery 3. Bacillary dysentery 3A. Chickenpox (Added L.N. 346 of 1998) 4. Cholera 5. Dengue fever 6. Diphtheria 7. Food poisoning 8. Legionnaires' disease 9. Leprosy 10. Malaria 11. Measles 12. Meningococcal infections 13. Mumps 14. Paratyphoid fever 15. Plague 16. Rabies 17. Relapsing fever 18. Rubella 19. Scarlet fever 20. Tetanus 21. Tuberculosis 22. Typhoid fever 23. Typhus 24. Viral hepatitis 25. Whooping cough 26. Yellow fever Dr Teresa Choi 13 Dr Teresa Choi 14 Environmental sanitation Sewerage management Safe drinking water Safe food Personal hygiene Sewerage management Drainage Services Department Primary and secondary wastewater treatment Flood control Dr Teresa Choi 15 Dr Teresa Choi 16 Sewerage Treatment Plants in Hong Kong Dr Teresa Choi 17 Dr Teresa Choi 18

4 Dr Teresa Choi 19 Dr Teresa Choi 20 Contain the foci of infection Prompt diagnosis, isolation, and treatment Identify and rectify sources of infection Surveillance of potential secondary cases Use of vaccine and chemoprophylaxis? Dr Teresa Choi 21 Dr Teresa Choi 22 Robust Control System Challenges Infrastructure Buildings Water Supplies Drainage Services Legal provision International regulations Local laws Institutionalized responses Hospitals Department of Health Food and Environmental Hygiene Department Education Effects of climatic phenomena Virulent strains Safety of recreational water and/or water not for drinking International travel and globalization Sustainability of individual alertness and maintenance of personal hygiene Dr Teresa Choi 23 Dr Teresa Choi 24

5 Strong association between the cholera series in the last two decades ( ) and El Nino, the climatic phenomena, has been found. V. Cholera strains Strain Period V.cholera O1 Classical Before 1961 V.cholera O1 El Tor 1961 ENSO and cholera: A nonstationary link related to climatic change? X Rodo, M Pascual, G Fuchs, and ASG Faruque. PNAS. 2002;99(20): V.cholera O Dr Teresa Choi 25 Dr Teresa Choi 26 Impact of new strains V.cholera O1 El Tor caused milder diseases, more subclinical infections, lower attack rates V.cholera O139 a result of transfer of O1 toxin gene to non-o1 V.cholera New strains modification of clinical presentation, carrier rates Chapter: 132 PUBLIC HEALTH AND MUNICIPAL SERVICES ORDINANCE FOOD BUSINESS REGULATION The quality of water for keeping live fish and shellfish as stipulated: E. coli less than 610 per 100 ml and absence of pathogenic organisms Dr Teresa Choi 27 Dr Teresa Choi 28 Preparedness for cholera epidemic? Robust control system in place Infrastructure Institutionalized responses Legal framework (international and local) What s more Bridge the knowledge gaps Vigilant surveillance End Dr Teresa Choi 29 Dr Teresa Choi 30