1. Epidemiologists, scientists who study the spread of disease, often focus on t
ID: 210497 • Letter: 1
Question
1. Epidemiologists, scientists who study the spread of disease, often focus on the basic reproduction number R0, which is the number of new infections created by the first infected individual. If this value is greater than 1, the disease will spread because each infected individual creates more than enough new infections to replace itself after recovery.
(a) For directly transmitted diseases, the value of R0 is found by multiplying the rate at which individuals are infected by the duration of infection. Suppose raccoons are infected with a parasite that persists in each individual for an average of 10 days. How many raccoons would need to be infected per day for the disease to spread?
(b) The infection rate is proportional to the contact rate, the rate at which individuals encounter each other. Suppose each individual is contacted with probability 0.01 each day, and a contact leads to an infection half of the time. How large would the population have to be for the disease to spread?
(c) How much would this value change if urban raccoons had a larger food supply and were less susceptible to infection, being infected only 20% of the time after contact with an infected raccoon?
**Please show your work as well, this is all the information given**
Explanation / Answer
a) For the raccoons to spread the disease, the R0 value should be greater than 1 which is calculated as rate at which individuals are infected * duration of infection
10 days * rate > 1
That is the rate should be 1 individual in 10 days.
b) if 0.01 is the contact probability then, the infection probability will be 0.01/2 = 0.005 since half the contacts lead to infection.
c) If the contact leads infection only 20% (1/5 times), then the infection probability becomes 1/5*0.01 = 0.002
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