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Epidemiology

Question
13 out of 184
 

Basic reproduction rate of infection best correlates to:



A Rate of contact with infectious person

B Frequency of new infectious cases on contact with each infectious person

C Probability of transmission of infection on contact

D infectious period of disease

Ans. B Frequency of new infectious cases on contact with each infectious person

1. Basic Reproduction rate or Ro is a measure in epidemiology which gives us the epidemic potential of a disease.

2. A fundamental parameter of infectious disease epidemiology is the transmission probability which is the probability that, given contact between an infective source and a susceptible host, successful transfer of the parasite will occur so that the susceptible host becomes infected.

3. Estimating the TP and its variability in population is important for understanding the dynamics of infection and the effects of interventions.

4. The TP depends upon the characteristics of the infective source, the parasite, the susceptible host, and the type and definition of contact. The infectious source could be another person, an insect vector or a contaminated inanimate object. (option c)

5. There are several methods for estimating the TP, In the first approach we present the conventional secondary attack rate while in the second we present the binomial model.

The concept of contact is very broad and must be defined in each particular study. The mode of transmission of a parasite determines what types of contact are potentially infectious.

The second important parameter in infectious disease is the Basic reproduction number Ro, which is defined as the expected number of new infectious hosts that one infectious host will produce during his or her period of infectiousness in a large population that is completely susceptible. Ro does include the new cases produced by the secondary cases, or further down the chain. It also does not include the secondary cases who do not become infectious. In general, for an epidemic to occur in a susceptible population Ro must be >1. If Ro is <1, an average case will not reproduce itself, so an epidemic will not spread.

For microparasitic infections, Ro is a composite of three important aspects of infectious diseases: the rate of contacts, the duration of infectiousness and the transmission probability per potentially infective contact.

So it is very clear that basic reproduction rate best correlates with the frequency of new infectious cases on each contact with an infectious person but it is computed by taking into account all the three other options.

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