INFECTIOUS DISEASE EPIDEMIOLOGY Instructors: Iman Ramadan, MD King Abdulaziz University Mary C. Smith Fawzi, ScD Harvard University

 Bioengineered e. coli (describe!)

ENTEROPATHOGENS  What are enteropathogens?  Microorganisms that are transmitted via contaminated food or water (fecal-oral transmission)  Bacterial, viral, and parasitic infections  Broad and heterogeneous group of pathogens  Greatest impact on young children; older children and adults acquire immunity from prior infections Nelson and Masters Williams, 2014

ENTEROPATHOGENS  Clinical manifestation:  Diarrheal disease– “three or more loose or watery stools in a 24-hour period”  Dysentery— blood in diarrhea  Identification of pathogens via fecal specimens  Highly preventable  Treatment- very successful  Antibiotics  Oral rehydration therapy Nelson and Masters Williams, 2014

TRANSMISSION ROUTES  Water  Food  Feeding utensils  Animals  Flies  Hygiene Nelson and Masters Williams, 2014

UNICEF State of the World’s Children Report, 2008

International Medical Corps, 2010; “Having received health education from International Medical Corps, her parents knew that left untreated for diarrhea and malnutrition Abida could die” (Eastern Afghanistan).

Millennium Development Goals Report, 2014

Nelson and Masters Williams, 2014

ENVIRONMENTAL RISK FACTORS  Poor water quality  Inadequate sanitation systems  Food quality  Crowded living conditions  Child care arrangements  Poor housing conditions  Prevalence/ incidence of other illnesses  Limited access to health care  Conditions of health care facilities Nelson and Masters Williams, 2014

HOST RISK FACTORS  Malnutrition  Children who are malnourished- 70% higher risk of diarrheal disease  Episodes are greater in severity and duration Nelson and Masters Williams, 2014

HOST RISK FACTORS  Micronutrient deficiencies  Reduction in capacity for intestinal mucosa to recover  Vitamin A (severity); supplementation ↓ diarrhea-related mortality  Zinc (incidence and duration) Nelson and Masters Williams, 2014

HOST RISK FACTORS  Age  Children  Under 2 years of age at greatest risk  ~ 800,000 children under the age of 5 worldwide died due to diarrheal disease (2010)  Elderly  Immunity  Increased susceptibility  Previous infection (e.g. measles, tuberculosis, typhoid)  Cycle of infection and malnutrition Nelson and Masters Williams, 2014

Annual age-specific incidence of diarrhea per 1000 person-years assessed by household surveillance in rural Bangladesh Kenrad and Masters Williams, 2014; Black et al., 1981

Kenrad and Masters Williams, 2014

HOST RISK FACTORS  Gastric acid  Serves as barrier  Antacids increase risk— episodes are greater in severity or frequency  Helicobacter pylori – related to stomach ulcer and cancer Nelson and Masters Williams, 2014

ENTEROPATHOGEN CHARACTERISTICS  Can vary by pathogen--Transmissibility  Pathogenicity  Proportion of infected persons who develop the disease  Virulence  Proportion who have the disease that experience severe illness  Anti-microbial resistance Nelson and Masters Williams, 2014

Kenrad and Masters Williams, 2014

EPIDEMIOLOGIC STUDY DESIGNS/APPROACHES  Prospective studies  Surveillance systems  Passive  Active  Outbreak investigations Nelson and Masters Williams, 2014

CONTROL STRATEGIES  Oral rehydration therapy  Zinc supplementation  Vitamin A supplementation  Maintaining/ increasing nutrition  Antibiotics (only when necessary)  Antimicrobials for some parasitic infections Nelson and Masters Williams, 2014

CONTROL STRATEGIES  Breastfeeding  Safer weaning of young children  Improved drinking water and sanitation  Hygiene practices  Measles vaccination  Vaccines for entropathogens (e.g. rotavirus) Nelson and Masters Williams, 2014

CONTROL STRATEGIES – Lives Saved Tool (LiST)  ORS  Zinc supplementation  Antibiotics for dysentery  Vitamin A supplementation  Rotavirus vaccine  Breastfeeding  Improved water and sanitation  UNICEF countries: reduced diarrhea-related mortality by 92%! Nelson and Masters Williams, 2014

CONTROL STRATEGIES  Diarrhea— second leading cause of child death in the world  ORT— how do we expand access? Nelson and Masters Williams, 2014

DISCUSSION ON ENTEROPATHOGENS  Why is incidence of enteropathogens so high?  Why are there so-many related childhood deaths?  Discussion here of inequalities and risk of infectious disease