Biology SimBio Questions Unit 1

All else being the same, which of the following changes will slow down the spread of the flu? A. A lower population density B. A lower transmission rate C. A longer infectious period (i.e. slower recovery)

A. A lower population density B. A lower transmission rate

All else being equal, which pathogen do you think would spread more quickly through a population? A. A pathogen that is transmitted through contaminated food or water. B. A pathogen that requires the exchange of body fluids between individuals.

A. A pathogen that requires the exchange of body fluids between individuals.

Direct Transmission A. HIV/AIDS B.COVID-19 C. Dysentery from Salmonella D. Giardia E. Bubonic Plague

A. HIV/AIDS B.COVID-19

Why do you think accounting for births and deaths changes the dynamics of measles in the population?

As new babies are born, the susceptible compartment (S) is replenished. When S increases sufficiently, transmission is more likely and another outbreak occurs.

How would reducing the size of a mosquito population by eliminating breeding habitat slow the spread of malaria?

By reducing the average number of contact events between mosquitos and people.

Which of the following microbes live in or on humans but do not necessarily cause disease?

C. albicans (fungi) E. coli (bacteria)

What is described by the movement of people between compartments in the SIR model?

Change in health status

What is the effect of wearing masks?

Masks flattened the curve by decreasing transmission when infected and susceptible Simploids came into contact.

How do vaccines slow the spread of a disease?

They reduce the likelihood an infected person will encounter an unvaccinated person before recovering from the disease.

Which type of pathogens are often described as not being truly "alive"?

Viruses

What is the minimum proportion of the population to vaccinate to establish herd immunity (Pc) if this flu has an R0 value of 4.0? Formula: Pc= (1-1/R0)

0.75

Above what threshold value of R0 will diseases spread?

1.0

Which of the following would cause an increase in the rate at which a disease spreads through a population? A. An increase in the frequency of contact between susceptible and infected individuals. B. An increase in the probability that contact between susceptible and infected individuals results in infection C. A decrease in the length of the infectious period

A. An increase in the frequency of contact between susceptible and infected individuals. B. An increase in the probability that contact between susceptible and infected individuals results in infection.

Which of the following statements about pathogens are true? A. Pathogens are infectious agents that cause disease. B. All microbes living on or in humans are pathogenic. C. All pathogens are parasitic.

A. Pathogens are infectious agents that cause disease. C. All pathogens are parasitic.

Which of the following statements about the basic reproductive number, R0, are true? A. R0 is the average number of infections caused by a sick individual in a population of susceptible individuals. B. R0 is estimated as the number of susceptibles multiplied by the transmission rate multiplied by the infectious period. C. A disease with R0 less than 1 will spread, while a disease with R0 greater than 1 will not spread.

A. R0 is the average number of infections caused by a sick individual in a population of susceptible individuals. B. R0 is estimated as the number of susceptibles multiplied by the transmission rate multiplied by the infectious period.

Which of the following are examples of barriers to help prevent pathogens from infecting tissues of the human body?

Acidic secretions, mucus linings, digestive enzymes.

How does widespread use of mosquito nets change the outcome of the simulation?

At equilibrium, the proportion of people and mosquitos infected with malaria decreased.

Which of the following statements about SIR models is always true?

At the end of an epidemic, everyone is in the Susceptible or Recovered compartment.

Based on the diagram, the length of the infectious period (L) directly affects the size of which compartment(s)? A. Susceptible B. Infected C. Recovered

B. Infected C. Recovered

Which of the following community mitigation strategies reduces the spread of disease by reducing the frequency of contact between infected and susceptible individuals? A. Vigorous hand washing B. Placing sick individuals in quarantine C. Wearing masks D. Using condoms during sex

B. Placing sick individuals in quarantine

Could bacteria or viruses reproduce in a dead organism?

Bacteria could, but viruses could not.

How do bacteria take advantage of their host to grow and replicate?

Bacteria use nutrients around the hosts cells to make new bacteria.

When the community adopted mitigation strategies but 20% of the population was noncompliant, which Simploids got sick?

Both compliant and noncompliant Simploids.

Indirect Transmission A. HIV/AIDS B.COVID-19 C. Dysentery from Salmonella D. Giardia E. Bubonic Plague

C. Dysentery from Salmonella D. Giardia E. Bubonic Plague

What generalities can you deduce from the diseases included on the map? A. Disease epidemics only occur in less developed countries. B. Disease epidemics can be controlled if people have access to modern medicine. C. Disease usually stay within one country. D. Disease epidemics vary widely in severity and scale.

D. Disease epidemics vary widely in severity and scale.

Which of the following pathogens must use the cellular machinery of its host in order to replicate? A. Bacteria B. Fungi C. Protozoans D. Viruses

D. Viruses

When infected individuals can recover, the disease spreads more slowly and not everyone gets sick. What else, do you think, would have a similar effect on disease spread?

Death from the disease

The highest proportion of the population gets sick with which conditions?

High population density, high transmission rate, long infectious period.

Slowing the spread of an epidemic would mean changing the shape of the epidemic curve. This curve is a time-based graph of which compartment of the SIR model?

Infected

How do you think adding births and deaths to the model will affect the course of a simulated measles epidemic?

Infections will rise and fall more rapidly.

The spread of a vector borne disease like malaria is driven, at least in part, by which of the following?

Interactions between susceptible humans and infected vectors.

How does social distancing lower the shape of the infected curve?

It lowered the peak number of infections, it delayed the peak number of infections, and it reduced the total number of infections.

Why did social distancing have an effect on how the flu spread through the Simploid population?

It reduced the frequency of contact between infected and susceptible individuals.

Recall that influenza is a respiratory disease. How would encouraging people to cover their mouths when they cough help reduce R0 below the threshold for disease spread?

It would reduce the transmission rate.

What types of pathogens cause malaria and Lyme disease?

Malaria is caused by a protozoan and Lyme disease is caused by a bacteria.

Based on the graph, which disease has the least uncertainty about the critical immunization threshold?

Measles

When R0 doubles, proportionally how many more people must be vaccinated to achieve herd immunity?

More than twice as many people if R0 is low, and fewer than twice as many people if R0 is high.

Which malaria control measures seek to reduce infections by lowering the frequency of contact between infected mosquitos and susceptible humans?

Mosquito nets Mosquito repellents (ie. bug spray)

How do mosquito nets affect the spread of malaria?

Nets reduce contact between infected mosquitos and susceptible people. Nets reduce contact between infected people and susceptible mosquitos.

Penicillin was discovered in 1928 and first used to treat bacterial infections in 1942. Derived from a mold (a fungus), penicillin disrupts the synthesis of bacterial cell walls. Given its mechanism, would you expect penicillin to work against a virus.

No

Based on the diagram, which of the following help determine the rate at which susceptible mosquitos are infected with malaria?

Number of susceptible mosquitos, number of infected humans, rate at which susceptible mosquitos bite infected humans.

Which approach most effectively limited the spread of flu for Simploids?

Social distancing and mask wearing combined.

What produces immunity to an infection?

The immune system identifies and "remembers" specific pathogens it has encountered.

If some individuals in the population have recovered from a previous smallpox infection, how would the required minimum proportion to vaccinate change?

The minimum proportion to vaccinate would be lower.

From the disease map on the previous page, which of the following do you think is important for assessing the impact of disease?

The mode of infection transmission, how easily the disease infects new hosts, how well people can fight of or recover from disease, the environment in which the hosts live.

Vaccines usually contain particles that are pieces of the virus or bacteria they target. How do you think this helps you avoid getting sick in the future?

The particles act as antigens, against which your immune system develops antibodies.

Imagine the vaccine is not 100% effective. Instead a fraction of vaccinated simploids do not develop immunity to the flu. How will the proportion of the population you should vaccinate to ensure herd immunity change?

The proportion to vaccinate will increase if efficacy of the vaccine is less than 100%.

For a disease that spreads more easily than smallpox, how would the minimum proportion to vaccinate for herd immunity change?

The proportion to vaccinate would be higher.

Which of the following statements about malaria is true?

The protozoan that causes malaria needs two host species to complete its life cycle.

Based on experiments, what can you say about how noncompliance affects community mitigation efforts?

The success of mitigation efforts declines as noncompliance increases.

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.

Community mitigation can both reduce the peak of the curve and delay when the peak occurs. Why might a community want to delay when the peak number of infections occurs?

To give researchers more time to develop vaccines and other treatments, and to give hospitals more time to increase their capacity (staff, equipment, etc)

Does widespread treatment with antimalarial drugs (ACTs) reduce the prevalence of malaria in the population?

Yes

Herd Immunity (critical immunization threshold) formula:

pc= (1-1/R0)

Formula for R0

R0- SBL (susceptible individuals * transmission rate * infectious period)

The critical immunization threshold for COVID-19 is most similar to that of which disease?

Smallpox