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PART B (Bpts) A new strain of the chickenpox arose in Farmtown (it was named roo

ID: 3041971 • Letter: P

Question

PART B (Bpts) A new strain of the chickenpox arose in Farmtown (it was named roosterpox). In order to characterize and control the epidemic, three investigators from the Centers for Disease Control and Prevention were assigned to investigate. In order to contain the disease, the investigators quarantined the whole town so nobody could move in or out of Farmtown. When the CDC investigators arrived, they identified all the Farmtown residents, totaling 35,750 people, of which 625 had already contracted roosterpox. Before the end of the first year of quarantine, 95 of these people died of the disease, and 225 new cases were detected. In addition, 705 people free of roosterpox died of other causes during that first year of follow- up. Assume none of the roosterpox cases could be considered free of the disease by the end of the year, and that the CDC investigators were immune. (Express rates per 1000,1 decimal place] WARNING: These questions are trickier than they might appear at first glance! 1) What was the prevalence of roosterpox at: (2pts each) a) the beginning of the investigation b) the end of the year

Explanation / Answer

1) the prevelance of roosterpox

(a) at the beginning of the investigation :625 persons had contracted roosterpox

(b) at the end of the year: 625+225=850 persons( it is given that none of the roosterpox cases could be considered free of the disease by the end of the year)

2) Number of cases of roosterpox=850

Number of residents=35750

Incidence of roosterpox among the residents of Farmtown during 1-year of quarantine=850/35750=0.0238=2.38%

3) Fatality rate=95/625=0.152=15.2%

4) Proportionate mortalitty for roosterpox

Number of deaths due to roosterpox=95

Number of deaths due to other disease=705

Total number of deaths=(705+95)=800

Proportionate mortality for roosterpox=95/800=0.119=11.9%