Disease Detectives B/C

[sciencenerd23]

Do I need to know Kochs postulates?

It was never on a test I took, but I guess it can't hurt to study it a bit.

Oh, can anyone recommend what food borne illnesses should be learned? Thanks!

[French_Toast]

Okay, I have some questions on some calculations problems that I messed up at our last invitational. I'll just give all the information that was made available, even if some is irrelevant.

Problem A(this was from Solon Division C Invitationals 2011, for anyone wondering)

Ate Specified Food Did Not Eat Specified Food
Food Item Ill Well Total Ill Well Total
Fisherman's Soup 25 25 40 20 39 59
Dobos Cake 17 38 55 28 16 44
Paprikash 43 47 90 2 7 9
Gundel Pancake 40 52 92 5 4 9
Goulash 20 1 21 25 53 78

After attending a retirement party for Louis Kossuth, many of his fellow Magyar nationalists developed gastroenteritis. All attendees were interviewed by the famed disease detective, Dr. Ignaz Semmelweis. Calculate the appropriate measure of association for each of the home-made food items shown in the table above.

I assumed that by "measure of association", they were referring to relative risk, which, based on the data, as well as my answers, seemed to be correct. I said:
Fisherman's soup - 1.844
Dobos Cake - .481
Paprikash - .469
Gundel Pancake - .782
Goulash - 2.966
And the only one that was counted wrong was the paprikash, which may have been due to a mathematical error on my part. It goes on to ask "For which food is the measure of association the largest?" and I correctly answered goulash.

Finally, it asked "Which of the food items do you think is most likely to have caused this outbreak? Why?". My answer of "Goulash, a measure of association that high over one is significant" was counted wrong. I'm not sure if I missed an important reason, or if the proctor was just confused by my wording, which, in hindsight, is really bad.


Thanks for any help, and if I'm correct and they were asking me to solve for relative risk, this is a good practice problem for anybody who wants to know what to study.

EDIT: Bah, the spacing didn't translate over from the post box to the actual post, so sorry for the table looking really bad. Hopefully you can still figure out which corresponds to which, if not, ask.

[butter side up]

Finally, it asked "Which of the food items do you think is most likely to have caused this outbreak? Why?". My answer of "Goulash, a measure of association that high over one is significant" was counted wrong. I'm not sure if I missed an important reason, or if the proctor was just confused by my wording, which, in hindsight, is really bad.

I actually said something similar, but it was marked wrong as well, and we expanded more than what you have written above. When we dissussed this with our coach, he said maybe they were looking for a few dishes, or something else such as contamination between a few different dishes.

Do I need to know Kochs postulates?

I have seen Koch's Postulates on a few tests, usually in passing. Once I simply had the question of which of a list of diseases was in compliance with Koch's Postulates.
Hope this helps!

[French_Toast]

Finally, it asked "Which of the food items do you think is most likely to have caused this outbreak? Why?". My answer of "Goulash, a measure of association that high over one is significant" was counted wrong. I'm not sure if I missed an important reason, or if the proctor was just confused by my wording, which, in hindsight, is really bad.

I actually said something similar, but it was marked wrong as well, and we expanded more than what you have written above. When we dissussed this with our coach, he said maybe they were looking for a few dishes, or something else such as contamination between a few different dishes.

That's entirely possible, as it does say "items". I'm gonna ask my coach about it on Monday and get his opinion.

[kalithepianist]

I'm sure this has been asked before, but should we know the symptoms of food-borne illnesses only, or other diseases as well? (For the state level.)

[The Eviscerator]

Probably not. The event is more of doing case studies, applying concepts, and some statistical analysis rather than diseases and specific symptoms. However, the person that writes the event could theoretically do anything so it might be good to just know some major ones.

[kalithepianist]

Some questions:

The population of Metroville was 3,187,463 on June 30, 2008. During the period January 1 through December 31, 2008, a total of 4,367 city residents were infected with HIV. During the same year, 768 new cases of HIV were reported, and 67 residents died as a result of HIV/AIDS. What is the prevalence per 100,000 population?

Using the information in the previous question, what is the incidence per 100,000 population?

(just want to make sure i'm approaching them correctly, thanks!)

[Legendary]

Finally, it asked "Which of the food items do you think is most likely to have caused this outbreak? Why?". My answer of "Goulash, a measure of association that high over one is significant" was counted wrong. I'm not sure if I missed an important reason, or if the proctor was just confused by my wording, which, in hindsight, is really bad.

I actually said something similar, but it was marked wrong as well, and we expanded more than what you have written above. When we dissussed this with our coach, he said maybe they were looking for a few dishes, or something else such as contamination between a few different dishes.

That's entirely possible, as it does say "items". I'm gonna ask my coach about it on Monday and get his opinion.

This is what our team put, and we answered it correctly, or correctly enough to get full points.

Paprikash and Goulash because they have the highest relative risk. Nearly all the people that ate Goulash were sickened and very few people that did not eat Paprikash got sick.

That's word for word what we wrote, and Paprikash was circled, so that was probably a determining factor.
Hope this helps.

[Flavorflav]

Okay, I have some questions on some calculations problems that I messed up at our last invitational. I'll just give all the information that was made available, even if some is irrelevant [...]

I don't check any of your math. First of all, there is a problem with your fisherman's soup data - 25 + 25 does not equal 40. Also, though, I get 2.1 for the risk from goulash - 20/21 divided by the baseline, which is 45/99 if I am reading your table correctly.

AHA- I just figured out what both you and, evidently, the event writers did. They compared "ate goulash" to "did not eat goulash" for their measure of risk. That's totally appropriate when you are considering a single risk factor or when you have potentially separate populations, but when you are dealing with a number of possibilities in a single population (as you are in this case), it means you are actually using a different standard of comparison for each one. I don't think I have ever seen that done in a real study, and I'm pretty sure it is a no-no.

ETA: Okay, I found out that it is acceptable to calculate RR this way. You did paprikash wrong, though - RR should be 2.15 by your method, 1.05 by mine. I'm guessing you did the fraction upside-down. It's a good illustration of why my way is better, though - the numbers involved in the "did not eat paprikash" are so small, they probably distort the RR by a great deal.

On an unrelated note, I'm curious as to what Kossuth was supposed to be retiring from. He was last elected to the Diet in 1867, two years after Semmelweis died. Somehow I doubt that he had a retirement party while fleeing from the Russian and Austrian armies in 1849, at which time Semmelweis was in Vienna in any case.

[Munchkin13]

Can someone tell me what the modes of transmission are??? Maybe also explain them a little bit too. I have my regionals this coming Saturday and I have no idea what they are. Someone please help me ASAP!! Thanks.