Detect and Confirm an Outbreak FETP Foodborne Outbreak Investigation, 2 June David T. Dennis, MD, MPH Medical Epidemiologist US Centers Disease Control and Prevention (CDC)

Detecting an Outbreak What is an Outbreak? –Occurrence cases of illness in a community or region exceeding the expected

Steps in Determining Outbreak 1.Detect unusual disease occurrence 2.Apply case definition 3.Validate and count cases –Time, place, person 4.Compare with baseline

Salmonellosis in passengers on a flight from London to the United States 12PM 12AM March 13March 14 Onset (3-hour periods)

Legionnaires' Disease By date of onset, Philadelphia, JulyAugust

Is a Peak in Cases Enough? Seasonality Surveillance artifact –Change in case definition –New laboratory test –Errors –Heightened sensitivity

Mortality surveillance

A/H1N1: percent positive by region and month,

Number cases SVP by month

Sources of Information on Illness Events Event-based (ad hc) Reporting –Physicians, nurses private settings –Hospitals, clinics (ICNs, Epis) –Schools, workplaces, camps –Medical laboratories –Rumors, news, concerned citizens Surveillance –Reportable diseases surveillance –Special surveillance systems Laboratory Epidemiologic

Surveillance Systematic collection, analysis, interpretation and dissemination of information for use in public health action

Appendix 1: List of 26 dangerous infectious diseases demonstrating to epidemic potential to be reported in the national surveillance system (Data sources: Decision No. 4880/2002/QD-BYT signed by Minister of Health) Note: Outbreak of any diseases must be reported immediately. Nationally Reportable Diseases, Vietnam 26 routinely, 9 immediately reportable dangerous diseases 7 related to food and waterborne agents –cholera –typhoid and paratyphoid –bacillary dysentery –amoebic dysentery –diarrhea –dysentery syndrome –Hepatitis A

Causes of Food-borne Outbreaks Preformed toxins –Bacillus cereus (1-6 hrs; N, V, cramps; rice) –Staph. Aureus (1-6hrs; N,V, D; ham, pastries; salads) –C. botulinum (12-36hrs; N,V,D, paralysis; home canned foods under anaerobic conditions) –Shellfish (algae) toxins (3-24hr) –Fish toxins (3-6 hr) –Mushroom toxins (early and late onset)

Causes of Food-borne Outbreaks In Vivo formed toxins –B. cereus (6-18hrs; D, abdominal pain) –C. botulinum (weakness, “floppy baby”) –C. perfringens (8-16hrs; D, abdominal pain) –E. coli (ETEC) (1-3days; D, abdominal pain) –E. coli (STEC) (3-8days; D, abdominal pain) –V. cholerae (1-3days; W-D, V, cramps, dehyd)

Causes of Food-borne Outbreaks Bacterial Tissue Invasion –Salmonella, non-typhi (12-120hrs; F,C,WD, N,V, F; eggs, meat, dairy) –S. typhi (systemic, F, abdominal pain, constipation; toxicity, perforation) –Shigella spp (1-2days; F,V,AC,WD, BD)

Causes of Food-borne Outbreaks Viruses –Hepatitis A (15-50days; F, fatigue, jaundice) –Noroviruses (24-48hrs; N, AP, V, D, F) Parasites –Amebiasis –Giardiasis –Cryptosporidiosis –Liver and lung flukes

Confirming Outbreaks and Cause: Example #1 New Hampshire State Epidemiology Office –Ad hoc telephone report by local hospital emergency room physician 3 cases acute abdominal cramps and diarrhea in children, no fever Sudden onset School-aged children Neighbors Onset late afternoon, after return from school Suspect school cafeteria –Investigative findings –Cause and source –Control and Prevention

Confirming Outbreaks and Cause: Example #2 New Hampshire State Epidemiology Office –Ad hoc reports local physicians and hospital cases with fever, cramps, diarrhea, some NV –Cases scattered throughout state, adults, secondary cases –All attended the same convention 2-7 days earlier –Cohort study identified salad prepared with raw egg dressing, high attack rate –Eggs from one farm, Salmonella enteriditis, test positive

Confirming Outbreaks and Cause: Example #3 New Hampshire State Epidemiology Office –Ad hoc report from local hospital emergency room –6 adults, tingling around mouth, tingling skin, itching hives, HA, rapid heart beat –Symptoms began while sharing a meal of bluefish at restaurant –Recovered remains of fish from outdoor garbage dump –Laboratory positive histamine poisoning.

Confirming Outbreaks and Cause: Example #4 Pennsylvania State Epidemiology Office –Notified by University of Pennsylvania student health clinic of hundreds of cases of “Green Death” –Acute onset of vomiting, abdominal pain, diarrhea in hundreds of students who attended football game in stadium 1-2 days before –Investigation revealed probably > 2 thousand cases, football team not involved, soft drinks implicated by case-control study –Team had own ice-machine; ice for drinks from well source next to a flooded stream in farming area; well found to be fecally contaminated –Is ice food or water?

Confirming Outbreaks and Cause: Example #5 Pennsylvania State Epidemiology Office –Ad hoc call from local hospital emergency room –18 persons seen with acute onset N,V, D, no fever –All had a history of eating pizza at restaurant A or home delivery –Case-control study multiple food items revealed mushrooms –Staph aureus toxin found in canned mushrooms from China; FDA investigation at factory in China identified problem in can washing at time of lid sealing

Thank You!