Transmission of infectious disease: modes & mechanisms of transmission
15 important questions on Transmission of infectious disease: modes & mechanisms of transmission
What is included in the mode of transmission?
In which two types can we separate disease transmission?
- Direct/short range transmission
- Indirect/long range transmission
Vector born
- mechanical (flies; hij gaat op je zitten)
- Biological (mosquito; only female can infect person)
What is a droplet and what is a aerosol?
Aerosol < 1micrometer
The smaller the further it goes through the air.
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Why is ventilation so important in term of protecting against aerosols?
What does a epidemiological curve show you?
Y-as: rate of increase of number of cases (thus not a absolute number)
X-as: period in months.
=> L-shape
You can plot it retrospectively or predictive epidemiological curves.
What is it called when the diagram is predictive? What kind of presumptions do they make in the beginning?
In covid: we did not know the details of transmission, risk groups etc. The red curve shows the predictive curve of covid.
Presumptions:
- Heterogenities in contact patterns
- Spatial variation: geographic variation with respect to genetics, age etc.
What did we see in the epidemiology curve of covid after social distancing? Why was this restriction so important?
Flattens the curve but, spread it out. Because there was no vaccin.
We had not enough beds in hospitals.
What would happen to the curve if the interventions were released again?
What does the R number mean? And what is the difference with the R0 number?
- based on natural history of the disease with mathematical models.
R0 = R at the start of an epidemic. In a naive population.
What is the R0 for measles virus? And what is the treshold?
This high R will continue until 95% of the population is immune. 95% is the threshold is 95.
If we compare SAR and R0 what do we see?
Name 3 determinant that influence the susceptibility to infection at the level of the individual.
- Do you have a receptor for the virus? Determines if you get infected and where.
- Pre-existing immunity
- Lung anatomy: where is the infection and can it shed (uitscheiden) beyond the tissue environment?
Which two determinants are important in disease development in a population?
- Patterns of social contact
- Mixing of age groups
How do you research transmission?
- Animal
- Human (not high risk diseases)
- Epidemiological studies (observational) (interventional; social control for example)
Name 4 determinants of disease development following infections; contagiousness.
- Where is the infection; nose, lung => influences the ease of onward transmission
- Do you know you have an infection => more contact with other people
- How many particles do you exhale?
- Level of immunity. Immunocompromised => long term producers of the virus. => supershedder.
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