Q2.16. During one of the measles outbreaks in the UK (above), what causes disease incidence to decline after reaching its peak? There are fewer and fewer susceptible people. Everyone dies of measles. The birth rate decreased. Check Answer
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The following question is about SIR (susceptible, infected, recovered) models. Remember, in SIR models you can plot the number of susceptible (S), infected (I), and recovered (R) individuals on the y-axis as a function of time (on the x-axis), resulting in a curve for each of the three groups. In your reading, a more realistic model of measles outbreaks is presented. Unlike the simple SIR model discussed earlier in the module, this model includes births, and it predicts that measles outbreaks should cycle over time. How do births affect the disease dynamics? A) Births increase the number of recovered (resistant) individuals in the population. B) Births increase the number of susceptible individuals in the population. C) Births increase the probability that infected people transmit the disease. D) Births themselves occur in cycles, decreasing herd immunity in pulses.
Madhur L.
The population of the village was about 10,000 on 1/1/2023, of which 1000 have a history of measles prior to 2023. During 2023, 900 subjects developed measles. During a survey carried out on 1/2/2023, 100 persons were found to be ill with the disease on that day, and 20 of them actually developed the disease on that day. During 2023, 90 of those who developed measles died from the disease, none of them died in January. Altogether, there were a total of 200 deaths from all causes in that population during that year. Assume there is no change on the population, and a single attack of measles provides life-long immunity. 1-Is the incidence proportion a meaningful measure of incidence in this example?
Rachel G.
Q6.2. There are many diseases that do not infect a person more than once, such as chicken pox and measles. What is responsible for this lifetime immunity? The acquired immune response, because antibodies are developed from previous infections. The acquired immune response, because it responds rapidly to broad classes of pathogens. Q6.3. A disease has been introduced to a population of 1,000 susceptible people. Infected people are contagious for about 3 days, and the overall rate of transmission between susceptible and infected people is 0.0002 (per day). Based on this information, is the disease likely to cause an epidemic? Why or why not? The disease is unlikely to cause an epidemic because R0 is less than 1.0.
Josee P.
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