Descriptive Epidemiology (Nursing)

00:01 Today we're going to talk about Descriptive Epidemiology.

00:05 Descriptive epidemiology describes disease outbreaks in terms of person, place and time.

00:12 Now there are two main objectives in descriptive epidemiology.

00:16 The first is to assess trends in health and in disease.

00:20 To do this, illnesses are monitored and comparisons are made.

00:25 Comparisons can be made by person.

00:27 For example, comparing trends between two different age groups.

00:31 We can also compare outcomes based on place by comparing trends in two different geographic areas.

00:38 And finally, we can also compare trends between different time periods comparing what happened today to what happened 10 years ago.

00:46 By making these comparisons, we assess trends in health and in disease.

00:52 These second objective of descriptive epidemiology is to identify problems and generate hypotheses.

00:59 So for example, if illnesses are occurring in a specific geographic area that could suggest an initial hypothesis for the source of an outbreak.

01:09 So let's take a look at person, place and time individually to learn what each entails for the specific epidemiological method.

01:19 Let's start with person.

01:21 Person refers to the socio-demographic characteristics of people who have an illness or disease.

01:27 It includes characteristics such as age, ethnicity, sex, gender, occupation, socioeconomic status.

01:35 This information is important to collect because individual socio-demographic characteristics and behaviors can increase or decrease the risk of developing an illness.

01:46 For example, infants and older adults are often at elevated risk for certain bacterial and viral infections.

01:54 The average age of cases as well as the minimum and maximum ages should be part of your descriptive analysis.

02:01 This allows us to understand which populations based on age are at highest risk.

02:06 By understanding these data, you can start to investigate possible sources.

02:12 Disease causing agents don't necessarily respect or follow geographic borders.

02:18 Investigating the location of cases can play a key role in determining the source of an outbreak.

02:26 For example, the distribution of cases in specific states could be a result of the availability of contaminated food product.

02:35 So if we see cases of illness and states A and B, but not in state C, then we can focus our attention on products that are distributed to states A and B but not C.

02:47 As you can tell, maps are useful tool in describing the spatial associations.

02:55 Now on to time.

02:56 Time refers to when and over what period of time an illness occurs.

03:01 Time is important in characterizing illnesses.

03:04 By examining time, we assess if incident rates or case numbers have increased or decreased over time.

03:13 The incubation period of a specific agent or the time between infection and symptom onset is another important aspect of time.

03:24 Together, information gathered within the categories of person, place and time provides a descriptive analysis of illness.

03:33 This information can be used to determine populations at risk, the source of the outbreak and it can be used to inform interventions that stop or prevent the spread of illness.

03:44 Okay, let's have some fun.

03:46 Let's use descriptive epidemiology to investigate an outbreak.

03:50 We'll start with person.

03:52 During one weekend, there were a total of 24 people who reported to three separate emergency rooms with GI complaints.

04:00 Because of the severity, salmonella is suspected.

04:04 Now let's investigate place.

04:07 All patients were asked to give a full food history that includes the locations of where they've eaten and where they've bought food in the past week.

04:16 12 of the patients reported eating homemade fried chicken at a barbecue.

04:21 9 reported making meals at their home with chicken purchased from the same local grocery store.

04:27 And the remaining three patients are all family members.

04:30 Although they're from out of town, they all ate chicken sandwiches from a local friend.

04:36 Now let's move on to talk about time.

04:38 All patients ate the chicken products within the past two days, some as early as hours before arriving in the emergency room.

04:46 So the time before ingesting the chicken and the onset of symptoms range from anywhere between 3 and 36 hours.

04:54 So based on this information, what's your hypothesis for the source of the illness? Based on what we know, it's likely that they all ingested contaminated chicken.

05:05 Chicken that was contaminated by salmonella.

05:08 Chicken that was likely sourced from the local grocery store.

05:12 This is an example of how we can use descriptive epidemiology to investigate outbreaks and identify the possible source of illness within a community.