Project #35701 - Assignment

Answer each question (1-5) in a 2-paragraph format (10-15 sentences):


1. Describe the following transmission types:





Which does/do you think has/have the potential to result in the largest outbreaks?



2. What is the basic reproductive number and what are its principle components? What are the limitations in determining and utilizing this number?


3. In the JAMA article "Trends in Infectious Disease Mortality in the United States During the 20th Century" found here the following graph of infectious disease mortality was presented. Describe this graph (I don't want an interpretation, just an objective description).

4.A physician has a patient with symptoms typical of influenza. He performs a rapid test in the office, which returns a positive result. He then collects a sample which is sent to the state public health laboratory. The lab uses a PCR test and finds that it is positive for influenza (type H1). At the same laboratory, a culture for influenza comes back negative. How would you explain these conflicting results? If you were performing surveillance for lab-confirmed influenza, would you consider this a case? Why or why not?

5. The sensitivity and specificity of a test are only two measures we use to describe the performance of a laboratory test. The positive predictive value of a test gives the probability that a positive result indicates the actual presence of disease (true positives divided by all positive), and the negative predictive value of a test gives the probability that a negative result indicates the actual absence of disease (true negatives divided by all negatives). • At the peak of flu season, about 30% of specimens submitted to the CDC are positive for influenza. This rate drops to about 1% in the off-season. • Say that you have a rapid influenza test with a 70% sensitivity and 95% specificity (the best possible scenario for rapid tests). • What would the predictive values (both positive and negative) be at the peak of the season and during the off-season?



Answer each question (6) in a 3-paragraph format (15-20 sentences):


6. Many of this week's readings focus on trends in infectious diseases over the last century with some discussion of the future. What sort of trends do you expect to see in infectious diseases over the next 25 years? Are there any pathogens or types of pathogens you expect to see increase or decrease? Why do you see these trends occurring?


Answer each question (7-9) in a 2-paragraph format (10-15 sentences):


7. Write thoughts, facts, and opinions on this topic below.

I believe we are going to see an increase in zoonotic illnesses due to the fact that we are encroaching on and encountering different animals as humans expand our territory and erode their natural habitats.  We will see many new viral diseases such as SARS, MERS CoV and chikungunya.  I think that chikungunya will soon spread to the US and eventually become endemic here as WNV and dengue virus has in certain areas of the country.  As I said before humans are causing massive amounts of destruction to natural lands and interacting with different animals in ways that have never occured before so we are being exposed to new pathogens which also have the possibility to interact with known existing pathogens and the possibility of shifts and drifts in DNA could lead to many new emerging infections. 


8. Write thoughts, facts, and opinions on this topic below.

There are a few things that I think about in terms of the future of infectious disease epidemiology. One is the type of diseases we are likely to encounter, another is the new technology we will rely on, and finally the new generation of epidemiologists that will hopefully have the skills to address new challenges using new technologies.


Based on environmental issues such as climate change, we are likely to see a change in the distribution of zoonotic disease. For example, Lyme’s disease is predicted to change exposure patterns in North America (Brownstein, Holford, & Fish, 2005). As climate impacts the migratory patterns of various animal vectors of disease, we will face new endemic diseases.


Another change in infectious disease epidemiology will be the availability of technology to predict and prepare for disease outbreaks. For example, statistical models can be used to predict events like zoonotic diseases linked to environmental conditions. Scientists are also getting better at predicting the strain of flu that will arise in the following year, based on improved knowledge of reproduction times, mutations, and genetics.


The most important factor in the future of infectious disease epidemiology is the epidemiologists themselves. We will certainly face challenges such as novel diseases and a changing environment that breeds new patterns of disease exposure. We will be armed with technological advances to try and prevent epidemics, yet it will be up to us to figure out new and innovative ways to use technology to predict outbreaks and prevent their spread. This will likely take creativity and interdependence on the many branches of public health (doctors, scientists, epidemiologists). Collaboration will be key to successfully preventing the spread of disease. 


9.  Write thoughts, facts, and opinions on this topic below.

Over the next twenty-five years, I expect to see an increase in antibiotic resistant strains of bacteria due to inappropriate community use by primary care physicians and by patients who don’t use the products properly.  The evolution of pathogens such as Staphylococcus aureus to Methicillin-resistant S. aureus or from bacteria in thetuberculosiscomplex (Mycobacterium tuberculosis, M. bovis, M. africanum, M. canetti, and M. microti) going from normal strains to multi-drug-resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB) show how quickly and easily this can occur.  On a positive note, I expect developments in anti-retrovirals to continue to reduce the number of cases of human immunodeficieny virus (HIV) positive individuals that progress into acquired immunodeficiency syndrome (AIDS).

 Like Clare, I believe that climate change will allow vectors to spread to additional areas where they previously could not go. While dengue fever is only endemic in United States (US) territories such as Puerto Rico and not actually on the continental US, Devin’s point about chikungunya is spot on as Florida has reported 81 cases this year.  Chikungunya, West Nile virus, and dengue fever are all carried by the Aedes aegypti and Aedes albopictus  (Asian Tiger) mosquitoes which are both endemic to the United States so they only need enough infected hosts to really start spreading these viruses. A. aegypti previously had been limited to elevations of no greater than one kilometer, but warmer temperatures have allowed them to be discovered at over 2200 meters in South America (Hopp, 2001). As the A. aegypti expands its range in South America and Africa and even in North America, then areas will need to begin to consider vaccination for yellow fever as well as prepare themselves for the scourge of dengue fever. In addition to climate change being a cause for an increase in cases of dengue fever, continued human population growth in these areas creates more hosts from which uninfected mosquitoes can get the disease and that population growth will also yield an increase in items like discarded plastic containers which will serve as ideal breeding grounds for new generations of mosquitoes (Hales, 2002).

 The speed at which goods are transported and the ease of travel for people are much greater than they were in times past.  Both of these allow for disease to be spread over a wider range and more quickly than previously.  Whether it is an insect or eggs in a shipping container or a person boarding a plane with a communicable respiratory infection, a disease now has better opportunities to find itself in new places in the world than it did before the invention of aircraft or the internet which allows for a globalization of the economy.  

 Over time, as water resources decrease, I expect that there will be an increase in waterborne disease as people try to find “free” water that might be less expensive, but will not have been treated for potential pathogens or parasites that might be lurking. 

Subject Science
Due By (Pacific Time) 07/19/2014 10:00 pm
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