Principles of prevention of Infectious Diseases

Prof. Martin P. GrobuschHead, Infectious Diseases Unit

University of the Witwatersrand andNational Health Laboratory Service

Hôpital Albert SchweitzerLambaréné, Gabon

PCMS 2007

Objectives

• to discuss host factors that influence exposure, infection and disease

• to understand routes of transmission of microorganisms

• to describe disease prevention and control measures at individual, institutional, community and global levels

• to assess risk, feasibility and cost-effectiveness of disease prevention and control strategies

• to characterise prevention strategies for infectious diseases at primary, secondary and tertiary levels of prevention

• Exposure prophylaxis Avoidance of malarious areas Mechanical prophylaxis

(ITNs, repellents)

• Vaccination• Intermittent Presumptive Treatment

• Chemoprophylaxis • Standby treatment• Treatment

Prevention and prophylaxis of ID –

malaria as an example

WHO childhood immunization schedule (EPI)

vaccine birth 6 w 10 w 14 w 9 mo

BCG Xoral poliovirus X X X XDPT X X XMeasles XYF1 Xhep B (scheme 1) X X Xhep B (scheme 2) X X X

1in selected countries

Reduction in vaccine-preventable diseases (USA) Gellin 1999

disease max. no. of cases reported cases % change

reported in pre- during 1997 (morbidity)

vaccine era

diphteria 206.939 5 - 99,99

measles 984.134 138 - 99,98

mumps 152.209 612 - 99,60

pertussis 265.269 5.519 - 97,92

polio (paralytic) 21.269 0 - 100,00

rubella 57.686 161 - 99.72

tetanus 1.560 43 - 97.24

Vaccines licensed in the USA in 1998:adenovirus, anthrax, BCG, botulinum toxin, cholera, diphteria, hep A, hep B, HIB, influenza, Japanese encephalitis, Lyme disease, measles, meningococcus A,C,Y, W-135, mumps, pertussis, plague, pneumococcus (23-valent), polio, rabies, rotavirus, rubella, tetanus, typhoid, varicella, yellow fever …

The concept of postexposure prophylaxis (PEP)

• Rabies

• HIV

• Tetanus

Guide to tetanus prophylaxis in routine wound management

Hx of adsorbed clean, minor wounds all other wounds

tetanus toxoid tetanus, tetanus Ig tetanus, tetanus Ig

diphteria diphteria

unknown or fewer yes no yes no

than 3 doses

3 or more doses no1 no no2 no

1unless > 10 y since last dose2unless > 5 y since last dose

Genesis of Hospital Infections

HOST

MICROBE ENVIRONMENT

Avoidance and interruption of nosocomial spread

Hand-washing Technique:

• 3 Types:– (“Social”) handwashing or

decontamination: soap and water

– Hygienic hand-washing: antimicrobial detergent; if non-aqueous, alcohol-based antiseptic used then termed hygienic handrub

– Surgical scrub

• 3 Stages:– Preparation– Washing and rinsing– Drying

Division I Births and Maternal Deaths, Vienna Lying-in,

Apr to Dec 1847

Month Births Deaths Mortality (%)

April May June July August September October November December

312 294 268 250 264 262 278 246 273

57 36 6 3 5

12 11 11 8

18.3 12.2 2.4 1.2 1.9 5.2 3.9 5.0 2.9

Arguments for Alcoholic Hand Disinfection

Rotter, ML. JHI(2001)48(Suppl A): S4-S8

• strongest and fastest activity against a broad spectrum of organisms

• more effective than soap and water in reducing the # of transient viable organisms on hands

• if well-formulated, less hand irritation and dryness than hand-washing with soap and water

• economy in time of application• useful where water not available (rural areas)

DEFINITION OF A “SHARPS INJURY” Devices associated with SI’s:

• disposable syringe• IV assembly• prefilled syringe• winged needle• vacutainer tube• IV catheters• other

At risk: ALL HEALTH CARE WORKERS/AUXILIARY STAFF

doctors, dentists, allied medical practitioners esp.. nursing staff, students, ambulance personnel, laboratory personnel, housekeeping staff, mortuary personnel, others

VICTIMS OF INADEQUATE DISPOSAL children, IVI drug abusers, etc.

AT LEAST 20 DIFFERENT PATHOGENS HAVE BEEN REPORTED TO CAUSE INFECTION FOLLOWING PERCUTANEOUS EXPOSURE TO BLOOD!

THOSE OF GREATEST CONCERN IN THE HEALTH-CARE SETTING ARE:

Hepatitis B virus (HBV) 6 – 30 %

Hepatitis C virus (HCV) 3 – 10 %

Human immunodeficiency virus (HIV) 0.25 - 0.4 %

Thank you for your attention!

Key references:Good evidence that in outbreak situations contaminated hands responsible for cross-infection (Infect Control & Hosp Epidemiol 1988;9:28-36; Critical Care Nursing Clinics of N America 1995;4:617-625)Effective hand decontamination significantly reduces ICU and GIT infection rates (The epic Project, UK, JHI 2001;47:23)Practical Guidelines for Infection Control in Health Care Facilities (WHO SEARO Regional Publication No. 41, WHO Manila 2004)Handwashing: a simple, economical and effective method for preventing nosocomial infections in intensive care units (J Hosp Infect 2006;62:395-405)