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

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


TRANSMISSION ROUTES

Water Food Feeding utensils Animals Flies Hygiene


UNICEF State of the World’s Children Report, 2008

International Medical Corps, 2010; https://internationalmedicalcorps.org/sslpage.aspx?pid=1861

“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



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 facilitiesNelson 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


HOST RISK FACTORS

Micronutrient deficiencies Reduction in capacity for intestinal mucosa to recover Vitamin A (severity); supplementation ↓ diarrhea-

related mortality Zinc (incidence and duration)


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 malnutritionNelson 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


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


Kenrad and Masters Williams, 2014

EPIDEMIOLOGIC STUDY DESIGNS/APPROACHES

Prospective studies Surveillance systems

Passive Active

Outbreak investigations


CONTROL STRATEGIES

Oral rehydration therapy Zinc supplementation Vitamin A supplementation Maintaining/ increasing nutrition Antibiotics (only when necessary) Antimicrobials for some parasitic infections


CONTROL STRATEGIES

Breastfeeding Safer weaning of young children Improved drinking water and sanitation Hygiene practices Measles vaccination Vaccines for entropathogens (e.g. rotavirus)


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%!


CONTROL STRATEGIES

Diarrhea— second leading cause of child death in the world

ORT— how do we expand access?


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

Documents

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