How is epidemiology used in public health?
Epidemiology is one of the most valued analytic tools we have in public health. It informs us what diseases and problems threaten the well being of the populace and how we should start dealing with them.A concrete example of this is the recent Chipotle food poisoning techniques. When large outbreaks happen you can plot out the number of cases and when they occurred to help give you a time frame of the attack. Then you can do patient interviews to figure out what exposure they all had in common. This helped with identifying Chipotle as the cause of the outbreak. With further analysis they were able to identify the vegetable prep step as the one that resulted in the exposure and now Chipotle has changed its prep procedures in response. We do epi on all kinds of problems such as the flu, HIV spread in segregated neighborhoods, and identifying risk factors for all sorts of cancer. Epidemiology is the hard backbone that makes up the science of Public Health.
Is incidence proportion the same as attack rate in epidemiology?
Yes, incidence proportion is the same as attack rate, and can be calculated as such:Incidence Proportion or Attack Rate = (number of new cases of a particular disease in a specified time interval) / (population at risk of developing the disease at the start of the time interval)
Is there a difference between "relative risk" and "relative rate" in epidemiology?
“Rate” is often used the same way as in chemistry, i.e. the risk that something happens in a short period of time, divided by the length of that time. So the scale is 1/time.“Risk” is simply probability. So the scale is just a number.If the outcome is death, for example, and the follow up time is 200 years, then the relative risk is 1 because the risk of dying within 200 years is 1 in each group. The relative rate is in principle defined only for a specific time point, i.e. we can compare the death rates in two groups on the 4th of April at 14h19:00, but in practice we will often estimate the risks of dying within a short period, say a year, and then refer to it as either the rate or the risk.tl;dr: in practice they are the same if we are talking about short follow up times.
How can you describe the epidemiology attack rate?
The attack rate is used as a measure of the portion of the individuals affected divided by the number of individuals at risk. It is a way to try and measure the aggressiveness of a specific disease, you basically calculate it from information such as number of individuals in a village and the number of reported cases of disease in the village. In an epidemic its often hard to judge how aggressive a disease is this in the beginning when not much is known about the disease. So you use this measure as the best estimate you're able to get.When you begin to get a grip on the disease you often try to calculate the basic reproductive number (R0), which basically describes how infectious a disease is (R0 is the number of secondary cases seen in a naive population if you introduce the disease). Measles has a high reproductive number of about 18, in other words it’s quite infectious and most susceptible individuals that are in the same room with a measles case will come down with the disease, while flu is considerably lower at about 3. The reproductive number on the other hand is a dynamic number and will change over the course of an epidemic, it is basically a measure of the current number of secondary cases which decreases over time as the number of naive in the population drops as a result of either being infected, recovered with immunity or dying, so each new case infects fewer individuals until such point as the reproductive number drops below 1.
What are important calculations required to measure an epidemic? Is it the combination of public health surveillance, morbidity rate, prevalence rate and the mortality rate of a population?
As always, it depends on the characteristics of the epidemic. The handful of measures you mentioned can be supplemented by many others if the situation is appropriate: The disease has the basic reproductive number (‘Ro’), incubation period (primary and secondary), case fatality rate, proportionate mortality ratio, incidence rate, period and point prevalence, duration, screening tests have sensitivity and specificity, positive predictive rate, negative predictive rate, and bacterial agents have mean generational times, growth rate profiles. Diseases have minimum infective doses, odds ratios, chi-square statistics, Fisher’s exact test probability statements, linear and multiple regressions, correlation, analysis of variance, and tests for normality, heterogeneity, and goodness of fit. This is just a taster; there are many more... If you want to become a field epidemiologist, you’ll need to handle numbers!
What is the difference between point prevalence and period prevalence?
Point prevalence is the number of persons with disease in a time interval (eg, one year) divided by number of persons in the population; that is, prevalence at the beginning of an interval plus any incident cases.Period prevalence is the proportion of a population that has the condition at some time during a given period (e.g., 12 month prevalence), and includes people who already have the condition at the start of the study period as well as those who acquire it during that period.Point prevalence seems to “pinpoint” a certain time interval.____________________________________________________________________________________FACTS:There were 50 people (the “pinpoint” or target) with flu in January 2017 (one month) in suburb of Detroit and a population of 1000, it is 1000/50=20% but we see no incident cases. So the POINT 50 people in the prevalence of 1000 population makes 20% of all of them got the flu in January 2017. So, specific to your question, 12.62% would have to be worked backwards to find the population tested and the people with flu compared to that…the point.Now PERIOD PREVALENCE seems to be a wide range of time, not a point of time. And a generalized summary of “already, and aquired” which can fluctuate widely and change daily. ie; Currently there is an epidemic alert for the flu of rapid onset of 12,000 new cases a day!I would say the question is referring to POINT because the month is specific; October, 2009. (A time interval). Since it is looking at schools, therefore students/individuals, it is also PINPOINTING (not a general unmeasurable amount of people or predictable disease.)
What is the difference between the definition of ratio, rate and proportion?
Let’s take an example, that example being uniform motion. Suppose you’re driving down the highway without slowing down or speeding up. And let’s suppose that in [math]12[/math] minutes you traverse [math]10[/math] miles. Then the rate that you’re traveling is [math]10/12[/math] miles per minute. That’s the same rate as [math]50[/math] miles per hour. The reason it’s the same rate is because of the proportion[math]\qquad 10:12=50:60[/math]there being 60 minutes in an hour. The expression [math]10:12[/math] is a ratio.A ratio [math]a:b[/math] is named by two magnitudes, the antecedent [math]a[/math] and the consequent [math]b[/math]. (Sometimes ratios are continued and are named by more than two numbers.)A proportion [math]a:b=c:d[/math] is a statement that two ratios [math]a:b[/math] and [math]c:d[/math] are equal.A rate [math]a/b[/math] is the interpretation of a ratio [math]a:b[/math] as a quotient.A bit more on ratios and proportionsThere are a few other terms that go along with ratios and proportions. Some aren’t used much anymore, but they all appear in Euclid’s Elements. Before the advent of symbolic algebra and equations, much of mathematics was described in terms of ratios and proportions.The ratio inverse to [math]a:b[/math] is the ratio [math]b:a[/math]. Taking the ratio [math]a:b[/math] jointly results in the ratio [math](a+b):b[/math]. Taking the ratio [math](a+b):b[/math] separately results in the ratio [math]a:b[/math]. Taking the ratio [math](a+b):a[/math] in conversion results in the ratio [math](a+b):b[/math].When [math]a:b=b:c[/math], [math]a:c[/math] is called the duplicate ratio of [math]a:b[/math]; when [math]a:b=b:c=c:d[/math], [math]a:d[/math] is called the triplicate ratio of [math]a:b[/math]. Essentially, these are the square and cube of the original ratio.The proportion alternate to [math]a:b=c:d[/math] is the proportion [math]a:c=b:d[/math].Before symbolic algebra, various rules for proportions were used to derive conclusions. For example, if [math]a:b=d:e[/math] and [math]b:c=d:f[/math], then, ex aequali, you may conclude that [math]a:c=d:f[/math]. Also, if two ratios are equal, then so are they taken jointly, taken separately, and taken in conversion.
If the incidence rate remains constant, what will happen to the prevalence of a disease with a duration of 4 years?
You need to make some assumptions to answer this question.The main assumption is that nobody dies of this disease, and the disease simply goes away after 4 years.An incidence rate is typically based on ANNUAL new cases. So, just plug some numbers in and do the math.So let us assume that 100 patients per year get this disease. These 100 people are sick for 4 years, and then they get well. In year number two, 100 more people get sick. They will also become well after an illness of four years. But NOW the PREVALENCE is 200 people in the population have the disease. Let’s go to year number 3, and add another 100. Now you have a prevalence of 300, and still nobody got well yet. The same goes for year number four, when your prevalence is 400. At this point, things begin to level off. In year 5, you get 100 new sick people, but the original 100 people get well. Your prevalence is still 400. I think you can see what will happen.Now the prevalence rate is across the population, and we are also assuming that the population is large in comparison to the number that gets sick to make the numbers simpler.