Lic. Andrés Juárez

VAST 2011 Challenge

Mini-Challenge 1 - Characterization of an Epidemic Spread

Authors and Affiliations:

Lic. Andrés Juárez – andres.a.juarez@gmail.com

Tool(s):

SPSS and Processing (The description is below)

Video:

http://www.youtube.com/watch?v=c0TE8h5OHMM

ANSWERS:

MC 1.1 Origin and Epidemic Spread: Identify approximately where the outbreak started on the map (ground zero location). If possible, outline the affected area. Explain how you arrived at your conclusion.

The epidemy triggered, without a doubt, on 05/18/2011, since the quantity of reports of desease people increases notoriously. However, would be risky to clearly indicate the area where it starts, due to the observation of reports of the same time but from different regions (see picture 1). It is possible to precise that after 8hs there is a high concentration of reports at the beginning of road 278, in Uptown and the east area of Downtown, although the increase of reports in east Downtown is not strange due to the high density of population during working hours and, also, where Vastopolis’ Hospital is located.

MC 1.2 Epidemic Spread: Present a hypothesis on how the infection is being transmitted. For example, is the method of transmission person-to-person, airborne, waterborne, or something else? Identify the trends that support your hypothesis. Is the outbreak contained? Is it necessary for emergency management personnel to deploy treatment resources outside the affected area? Explain your reasoning.

a) How is transmitted the infection?

Taking as reference 05/18/2011, beginning day of the epidemic outbreak, we observe that the diseases reports tend to produce westward. Observing the wind direction of that day, indeed, has an orientation to the west. Therefore we could suppose that the infection spreads by the wind’s action. We can’t discard a person-to-person contagion either, since there is an abrupt increase of reports of Downtown area, where there is a high population density during working hours. Has to be taken into consideration that 05/18 was a Wednesday, in other words; a working day, and the epidemic spread also remained during Thursday and Friday.

We dismiss the hypothesis that the disease is transmitted by water. Even though there are just a few reports on the surrounding areas of the riverside, they are not significative in relation to the total amount of reports (see picture 2).

b) Is the epidemic spread contained?

According to the data extracted from the population density file, where is perceived the difference between the residents and the density during the day, we can observe a great exchange of population between the different areas, as for example, Downtown goes from a population of a little more than 89,000 to a population of almost 260,000 during working hours. However, the totals remain exactly the same either during working hours or the rest of the time. We deduce then that Vastopolis is a closed area, meaning that there is not an exchange with the outside (or is negligible) but just an internal exchange.

On the other hand is observed that 05/20/11 had an important volume of disease reports, but declined abruptly during the last few hours until not have any reports at all by the last hour of that day.

In any case, the presence of an airport and freeways indicates a possible exchange with the outside that we should be prevented of. Even more, taking in consideration several cases reported in adjacent areas of the airport (see picture 3)

c) As a way to conclude the previous point, even though the reports of new cases decreased greatly in the last hours of 05/20/11, is recommended to restrict the external exchange with the purpose of not spread the epidemy to other regions. So, would be recommended to remain the airport closed and perform sanitary controls on roads of the metropolitan border, until guarantee that the epidemic spread is under control.

The investigation was performed, basically, utilizing the software SPSS and Processing.

SPSS used to analyze the data and discarding, from the more than a million messages, those that inform about a symptom or sorrow. Next, took only the ones indicating their own symptoms and not somebody else’s. Finally, unified those proceeding from the same person with the objective of not reporting new cases.

Once realized the previous filtering, the database contained 18,172 cases, and got processed with the Processing software, marking the day (04/30 as day zero) and the hour (from 0 to 23). With the coordinates, started marking dots by day on the map, counting them. Those dots darkened on the areas of higher density.

Was able to observe that, until 05/18/11, there was always a stable amount of reports, deduced as everyday reports of any population (name angina, cold, etc.). Since 05/18/11 was observed an important increase of the quantity of reports, which remained until 05/20/11, declining on the last hours. Without having a new report during the last hour of that day, as indicated on points b and c of MC 1.2.