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scio444 wrote:Okay, so on epi-curves- I know that the unit of time should be 1/3-1/4 of the typical incubation period. But I have been noticing that only multiplying the time unit by 3 is giving me an incubation period that falls within the range on the answer keys. Any thoughts on this? What numbers do you guys use?

I found a discussion of it in Michael Gregg’s book, Field Epidemiology, chap 6, The Field Investigation. That section was written by Bob Fontaine and Rick Goodman. (btw - Rick is one of the folks who came up with the idea of a Disease Detectives event in the Science Olympiad.) They say “The choice of the time interval used is critical. Intervals that are too short (like hours for diseases with long incubations) may overemphasize random noise in the underlying pattern and hinder interpretation. Intervals that are too long (like weeks for diseases with short incubation periods) will group many cases into a few intervals and obscure the real pattern. As a general rule, intervals between one-fourth to one-half an incubation/latency period work best at revealing the time pattern of an epidemic. As numbers increase, shorter intervals will reveal more detail to the pattern.” (p 88 2nd edition)

The incubation period is the time period between exposure and onset of an infectious disease. The term “latency period” is similar but often used with chronic diseases. The idea here is the scale you use for the X-axis affects the usefulness of the curve. Let’s say you have a salmonella outbreak where 50 people get sick over a 3 day period. If you mark off the X axis in minutes, your X axis would be at least 60min/hrX24hr/dayX3days or 4320 intervals long. There would be a lot of blank space between the 50 cases and few, if any, points would have more than one case. If you were to mark off the X axis in weeks, all 50 cases would be in the same space. That does not tell you much either. If you use day, you will have data for 3 points and you could probably show a start, peak and end. If you were to break in down into 8 or even 12 hour intervals, your graph would become more interesting.

While I might use the incubation period as the basis for setting my X-axis intervals, I would not put much faith in using X-axis interval as the basis for determining the incubation period for an outbreak where I did not know the bug that was causing it. I would much rather use distance between peaks if I had them.

Thank you very much!

Is Disease Detectives going to be the same next year for Div B?

hmath729 wrote:Is Disease Detectives going to be the same next year for Div B?

What do you mean "the same"? What would you like to see changed and why do you think it should change? The rules are set by National but they really do want to make things better. We all want the events to be fun but they should also be challenging. When I give a test to a class - I want everyone to get a 100. That would be a disaster in a Disease Detectives competition so I deliberately put in some questions that I think no one will be able to answer. I usually find that one or two teams get it correct.

hmath729 wrote:Is Disease Detectives going to be the same next year for Div B?

Disease Detectives will pretty much stay the same except for the fact that the new rotation is Population Growth. The main focus will be towards Water Quality, Water Pollution, Sanitation Needs, Growth of Slums and Household Environment, Air Pollution, Infectious Disease Outbreaks, Rapid Spreads of Diseases through Public Transportation and Air Travel, Food Quality and Contamination, Environmental Problems, Behavioral Problems, Injuries, etc.
Hope this helps!

okay so HOW do you guys study for disease? Is there any good text books or just looking off things from handouts.

Well, my partner and I usually get our information from the CDC Website. We've noticed that a lot of Invitational/Regional/State tests have a lot of information from this website. If you haven't already checked it out then I would recommend starting there. Also, if you go to the public library, just pick up a few books on diseases. There is a LOT of credible information on diseases in the library! If you do happen to stop by the library , go with your partner. It really helps knowing the strengths and weaknesses of your partner when you're taking the test!

mkb14954 wrote:Well, my partner and I usually get our information from the CDC Website. We've noticed that a lot of Invitational/Regional/State tests have a lot of information from this website. If you haven't already checked it out then I would recommend starting there. Also, if you go to the public library, just pick up a few books on diseases. There is a LOT of credible information on diseases in the library! If you do happen to stop by the library , go with your partner. It really helps knowing the strengths and weaknesses of your partner when you're taking the test!

thank you!

For statistical stuff, search Epidemiology. I found a couple pretty good online texts (pdf) to read through.

nomynameisnotkevin wrote:For statistical stuff, search Epidemiology. I found a couple pretty good online texts (pdf) to read through.

ik they have some of the statistical stuff on the training handout, but i never saw any of them in any of my states' regionals and states. Are those things might actually appear on the tests or we can actually ignore them