NR503 Population Health, Epidemiology and Statistical Principles Midterm Exam

NR503 Population Health, Epidemiology and Statistical Principles Midterm Exam
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Student IConsult

Chapter I2-4

Which Iof Ithe Ifollowing Iis Ia Icondition Iwhich Imay Ioccur Iduring Ithe Iincubation Iperiod?

• Transmission Iof Iinfection
The Iincubation Iperiod Iis Idefined Ias Ithe Iinterval Ifrom Ireceipt Iof Iinfection Ito Ithe Itime Iof Ionset Iof

clinical Iillness. IAccordingly, Iindividuals Imay Itransmit Iinfectious Iagents Iduring Ithe Iincubation
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I period Ias Ithey Ishow Ino Isigns Iof Idisease Ithat Iwould Ienable Ithe Iisolation Iof Isick Iindividuals Iby

I quarantine.

Chicken Ipox Iis Ia Ihighly Icommunicable Idisease. IIt Imay Ibe Itransmitted Iby Idirect Icontact

I with Ia Iperson Iinfected Iwith Ithe Ivaricella-zoster Ivirus I(VZV). IThe Itypical Iincubation Itime Iis

I between I10 Ito I20 Idays. IA Iboy Istarted Ischool I2 Iweeks Iafter Ishowing Isymptoms Iof Ichicken

I poxIincluding Imild Ifever, Iskin Irash, Iand Ifluid-filled Iblisters. IOne Imonth Iafter Ithe Iboy

I returned Ito Ischool, Inone Iof Ihis Iclassmates Ihad Ibeen Iinfected Iby IVZV. IThe Imain Ireason

I was:

• Contact Iwas Iafter Iinfectious Iperiod
• Subclinical Iinfections Iwere Inot Iyet Idetected
• Disease Iwas Iendemic Iin Ithe Iclass
The Idisease Iis Ispread Iby Icontact Iwith Ian Iinfected Iindividual Iwho Ican Itransmit Ithe Iagent I(VZV) Ito

immunologically Inaive Ipersons Iduring Ithe Iincubation Iperiod Iand Ifor Iseveral Idays Iafter Ionset Iof
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I clinical Iillness. ISince Ithe Iboy Istarted Ischool I14 Idays Iafter Ishowing Isigns Iconsistent Iwith Ichicken

I pox, Iit Iis Imost Ilikely Ithat Ihe Iwas Ino Ilonger Iinfectious.

The Iability Iof Ia Isingle Iperson Ito Iremain Ifree Iof Iclinical Iillness Ifollowing Iexposure Ito Ian

infectious Iagent Iis Iknown Ias:
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, • Hygiene

• Vaccination
• Herd Iimmunity
• Immunity
• Latency
Immunity Iis Ithe Icapacity Iof Ia Isingle Iindividual Ito Iavoid Idisease Isusceptibility Iwhen Iexposed Ito

I an Iinfectious Iagent. IHerd Iimmunity Iis Ia Ipopulation Icharacteristic. IFor Icertain Idiseases, Iindividual

immunity Ican Ibe Iacquired Iby Ivaccination, Ibut Ithis Iis Inot Itrue Ifor Iall Iinfectious Idiseases.
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Which Iof Ithe Ifollowing Iis Icharacteristic Iof Ia Isingle-exposure, Icommon-vehicle Ioutbreak?

• Long Ilatency Iperiod Ibefore Imany Iillnesses Idevelop
• There Iis Ian Iexponential Iincrease Iin Isecondary Icases Ifollowing Iinitial Iexposures
• Cases Iinclude Ionly Ithose Iwho Ihave Ibeen Iexposed Ito Isick Ipersons
• The Iepidemic Icurve Ihas Ia Inormal Idistribution Iwhen Iplotted Iagainst Ithe Ilogarithm Iof Itime
• Wide Irange Iin Iincubation Itimes Ifor Isick Iindividuals
Single-exposure, Icommon-vehicle Ioutbreaks Iinvolve Ia Isudden, Irapid Iincrease Iin Icases Iof Idisease

that Iare Ilimited Ito Ipersons Iwho Ishare Ia Icommon Iexposure. IAdditionally, Ifew Isecondary Icases
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I develop Iamong Ipersons Iexposed Ito Iprimary Icases. IA Ihistogram Iof Ithe Ioutbreak Ican Iplot Ithe

I number Iof Icases Iby Itime Iof Idisease Ionset. IIn Isingle-exposure, Icommon-vehicle Ioutbreaks, Ia Ilog

I transformation Iof Ithe Itime Iof Idisease Ionset Iwill Ioften Itake Ion Ithe Icharacteristic Ishape Iof Ia Inormal

distribution I(i.e., Ia Ibell Icurve) Iwith Ithe Imedian Iincubation Itime Ifound Iat Ithe Ipeak Iof Ithe Icurve.
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What Iis Ithe Idiarrhea Iattack Irate Iin Ipersons Iwho Iate Iboth Iice Icream Iand Ipizza?




• 39/52
• 21/70
• 39/67
• 51/67

, • none Iof Ithe Iabove
The Iattack Irate Iin Ithis Iexample Iis Idefined Ias Ithe Inumber Iof Ipersons Iwho Idevelop Idiarrhea Idivided

by Ithe Itotal Inumber Iof Ipeople Iat Irisk. IIn Ithis Iexample, Ithe Iat-risk Igroup Iis Ithose Iwho Ihave Ieaten
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I both Iice Icream Iand Ipizza. IOf Ithese I52 Ipersons, I39 Ideveloped Idiarrhea.

What Iis Ithe Ioverall Iattack Irate Iin Ipersons Iwho Idid Inot Ieat Iice Icream?

• 30%
• 33%
• 35%
• 44%
• 58%
(14+9)/(40+30)= I33%

The Iattack Irate Iis Ithe Inumber Iof Ipersons Iwith Idiarrhea I(14 I+ I9) Idivided Iby Ithe Itotal Inumber Iof

persons Iwho Idid Inot Ieat Iice Icream I(40 I+ I30).
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Which Iof Ithe Ifood Iitems I(or Icombination Iof Iitems) Iis Imost Ilikely Ito Ibe Ithe Iinfective Iitem(s)?

• Pizza Ionly
• Ice Icream Ionly
• Neither Ipizza Inor Iice Icream
• Both Ipizza Iand Iice Icream
• Cannot Ibe Iassumed Ifrom Ithe Idata Ishow
Among Ipersons Ieating Iice Icream, Iover I70% Ideveloped Idiarrhea Iregardless Iof Itheir Ipizza

I consumption I(39/52 Iand I11/15). IAmong Iboth Igroups Iof Ipersons Iwho Idid Inot Ieat Iice Icream, Ieach

attack Irate Iwas Iequal Ito Ior Iless Ithan I35% I(14/40 Iand I9/30).
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Which Iof Ithe Ifollowing Ireasons Ican Iexplain Iwhy Ia Iperson Iwho Idid Inot Iconsume Ithe Iinfective

food Iitem Igot Isick?
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• They Iwere Idirectly Iexposed Ito Ipersons Iwho Idid Ieat Ithe Iinfective Ifood Iitem
• Diarrhea Iis Ia Igeneral Isymptom Iconsistent Iwith Ia Inumber Iof Iillnesses
• There Imay Ihave Ibeen Ian Iinaccurate Irecall Iof Iwhich Ifoods Iwere Ieaten

, • All Iof Ithe Iabove
• None Iof Ithe Iabove
Without Iknowledge Ias Ito Ithe Ispecific Iagent Iin Ithis Iinstance, Iit Iis Ialso Ilikely Ithat Iit Ican Ibe Ispread

I by Idirect Icontact Iwith Iinfected Ipersons. ISince Idiarrhea Iis Ia Igeneral Idisease Isymptom, Iit Iis

I possible Ithat Iseveral Iinfectious Iagents Imay Ibe Ipresent Iat Ithis Imeal Ior Iothers Ieaten Iduring Ithe

I same Itime Iperiod. IFurther, Iinformation Iregarding Ifood Iconsumption Imay Ihave Ibeen Icollected

I long Iafter Ithe Idisease Iepisode. IThis Imay Ihave Iled Ipersons Ito Iincorrectly Iremember Ithe Ifoods Ithat

they Iconsumed.
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An Ioutbreak Iof Igastroenteritis Ioccurred Iat Ia Iboarding Ischool Iwith Ia Istudent Ienrollment Iof

846. IFifty-seven Istudents Ireported Isymptoms Iincluding Ivomiting, Idiarrhea, Inausea, Iand
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I low-grade Ifever Ibetween I10 Ip.m. Ion ISeptember I24 Iand I8 Ip.m. Ion ISeptember I25. IThe Iill

I students Ilived Iin Idormitories Ithat Ihoused I723 Iof Ithe Istudents. IThe Itable Ibelow Iprovides

I information Ion Ithe Inumber Iof Istudents Iper Itype Iof Iresidence Iand Ithe Inumber Ireporting

I illnesses Iconsistent Iwith Ithe Idescribed Isymptoms Iand Ionset Itime. ICalculate Ithe Iattack

I rateIamong Iall Istudents Iat Ithe Iboarding Ischool.




57 Itotal Icases/ I846 Itotal Istudents=6.7%