Question

354 EAK IN THE CAPSTONE CASE A: HEPATITIS A OUTBREAK MIDWEST By Catherine Dentinger and Steven T. Fleming cases of hepatitis JL (1990 population ne first 30 weeks 5) was reported 5). In County anti-HAV) were inued from previous CITY ONE OUTBREA Case Definition: Apr with a discrete onset ber 3, 1998, who wa link to a laboratory October 15 and Dece Case Finding: The N county health depa requested counties state. County R He: ing all emergency county and encour with hepatitis A. ing county health report cases with Data Collection: ing the case defin graphic characte BACKGROUND On December 1, 1998, the CDC was notified of 48 cases of in County R (1990 population 126,137) and County L (100 462,361). Midwest State. By comparison, during the first a 1998, an average of seven cases per week (range 3-15) was in the entire Midwest State (1990 population 10,847.115). In 28 ill persons with IgM antibody to hepatitis A virus (anti- reported to the county health department with onset of sym between November 14 and November 27, 1998; 18 (64 percent these patients reported eating at one local restaurant (Resta during their incubation period. However, no ill food handlere rant A had been reported. In County L, 19 IgM anti-HAV-positive sons were reported, with dates of symptom onset between No een November 6 and November 18. The 17 patients interviewed lived in the wester part of one city, and 12 (71 percent) reported eating at a local resto rant (Restaurant Y) during their incubation period. No ill food handle at Restaurant Y had been reported. Counties R and Lare separated a distance of approximately 100 miles; no links between Restaurant and Restaurant Y had been identified. with onset of symptoms rant (Restaurant A) andlers at Restau QUESTIONS 1. Would you call this an epidemic or an outbreak? 2. What are the steps in an outbreak investigation? 3. Hepatitis A is a viral pathogen. What are the broad categories of diseases that one must consider when investigating a gastrointestinal disease outbreak? 4. What characteristics can be used to describe infectious agents (infectivity, pathogenicity, virulence)? 5. What measures of morbidity would you use to estimate infect pathogenicity, and virulence? 6. What are the different modes of transmission? Describe the possible routes of transmission. 7. How would you characterize hepatitis A? CDC Viral Hepati questionnaire w reported by Dec eaten at any of ing the initial in molecular studi Investigation taurant A: Curr drawn for sero members were item and meth Results: As of reported to G were male; th cases were illness. Date: 4. 1998. All 42 ca October and who were al ſcontinued

Answer 1

1. It will be called an outbreak as it is also similiar to epidemic that is sudden increase in cases of a disease but in a limited area instead of an entire region.

2. Steps in outbreak investigation are:

1. field work preparation : it includes team formation, tools and supplies, lab facilities to investigate the cases.
2. establishment of outbreak existence: it is done by analysing the clinical profile and case records of reported cases.
3. diagnosis verification is done by collecting adequate lab samples of cases and their contacts
4. definition and identification of cases by using a defined set of criteria.
5. describing and orienting data by comparing current data with already existed data related to that specific disease and finding the population at risk.
6. developing, evaluating and refining hypothesis by medical, lab and epidemiological investigation
7. implementing control and prevention measures after confirmation of outbreak. It involves vaccination of population at risk, medical management of cases etc
8. dissemination of finding by providing daily updates, interim report and monitoring the situation, acknowledging if outbreak is over.

3. bacterial causes of gastrointestinal illess are staphylococcus, shigella, campylobacter, salmonella and e coli in contaminated food items.

protozoal causes include entamoeba histolytica and giardia lamblia

4. characteristics to define infective agents are:

Infectivity is ability of pathogen to cause infection in a host

pathogenicity is the ability to cause a disease

virulence is the ability to cause serious disease in host

immunogenicity is ability to cause immune response in host