The hospital uses municipal water and sewage services. There had been no work on

Question

The hospital uses municipal water and sewage services. There had been no work on water or sewage lines in the past year nor recent roadwork or digging around the hospital. The hospital dining service included two cafeterias. The main cafeteria served as the primary arena for all food storage, preparation, cooking and delivery to 100% of patients in the hospital. Visitors also ate at this main cafeteria. The specific facilities within the main cafeteria served hot entrees, a grill, deli bar, and salad bar. A second smaller cafeteria at the hospital offers menu selections with a per item cost and predominantly is used by hospital staff. Under the advisement of your State epidemiologist, you begin interviewing the sick hospital patients to better understand the likely source of the outbreak. Among the 20 patients interviewed (6 had been discharged and were no longer at the hospital), 25 had eaten food from the deli bar; 9 had eaten food from the salad bar, and 3 from the grill. Seven-day food histories revealed no particular food item that was common to all or most of the patients. It was also noted in the labor and delivery ward that none of the newborns were exhibiting symptoms. Given this information, what is your leading hypothesis on the mode of transmission in this outbreak? What studies or other investigations would you initiate to explore this hypothesis. Provide some descriptive epidemiology on the nature of this outbreak and the likely culprit in terms of the epidemiological triangle. As the health department epidemiologist, please list your next priorities and discuss them in relation to the steps of this outbreak investigation.

Explanation / Answer

H1-The Mode of transmission for the outbreak of disease is through oral-fecal route.

H2- The clients who have Consumed water from the Main canteen are exposed to the contract of microorganism.

A descriptive incidence study, would be appropriate to explore the hypothesis.

The next priority would be to study the Agent Host environmental factors of epidemiogical triad and to break the interaction among them to control and prevent the Outbreak.

The basic triad of descriptive Epidemiology are.

Agent

In infectious disease models, the term "agent" originally referred to the entity or micro-organism (e.g. virus, bacterium) capable of causing the disease. As a general rule, the agent must be present for the disease to occur. However, the mere presence of the agent is not always sufficient for the disease to occur.

Host

"Host" refers to the organism (e.g. human) capable of being infected by a specific agent. There are intrinsic factors that influence an individual's exposure, susceptibility or response to a causative agent.

Environment

The environment is all that is external to the host. Environmental factors are extrinsic factors that affect the agent and the opportunity for exposure. They can be physical factors (e.g. climate), biological factors (e.g. insects) or socio-economic factors (e.g. sanitation, access to health services).

The steps in Descriptive Epidemiology are:

STEP 1: DEFINING THE POPULATION

The defined population- i) could be a whole geographic region or a representative sample ii) could be a specially selected group- based on age, sex, occupation, etc iii) should be large enough so that it is meaningful iv) should be stable without migration into or out.

STEP 2: DEFINING THE DISEASE The epidemiologist defines the disease which can be measured and identified in the defined population with a degree of accuracy. This is different from the clinician’s definition of a disease

3: DESCRIBING THE DISEAS-Time, Place. Person

Time-Year, Season Month, Week Day, Hour of onset ,Duration

Place-Climatic zones Country, Region Urban/Rural Local community, Towns, Cities, Institutions.

Person-Age Sex Marital state Occupation, Social status, Education Birth order Family size Height Weight Blood

pressure, Blood cholesterol, Personal habits

STEP 4: MEASUREMENT OF DISEASE Types- 1) Cross sectional studies- Prevalence can be obtained. It is based on a single examination of a cross section of population at one point in time. More useful for chronic diseases .

Longitudinal studies- Incidence can be obtained. The observations are repeated in the same population over a prolonged period of time by means of follow up examination. Longitudinal is more useful, but it is time consuming.

STEP 5: COMPARING WITH KNOWN INDICES -Comparisons are made with known indices to arrive at clues to the disease’s etiology

STEP 6: FORMULATION OF A HYPOTHESIS -A hypothesis is a supposition, arrived at from observation or reflection . An epidemiologic hypothesis should specify- The population- characteristics of the people to whom the hypothesis applies Specific cause and Expected outcome-the disease

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