When we hear about a new disease outbreak, the news is frequently followed by general information about how the disease has spread and which region it’s currently infecting. In the weeks following this announcement, however, we also learn about where the disease originated, where it is going and the likelihood of it spreading internationally. Eventually, we may even see real-time maps of this data and predictions of what’s to come.
But where do epidemiologists gather all of this data? How are they able to look at a disease outbreak such as measles and determine that the original case spread from Disneyland in California?
The answer to these questions lies with geographical information systems, or GIS. GIS is a sophisticated mapping technology that allows specialists to enter data, enabling them to track the spread of diseases and predict where the disease is most likely to proliferate based upon a number of pre-determined factors. This data can help prepare areas that expect to be hit with an outbreak, as well as providing statistics on the rate of spread and mortality. Furthermore, visualizing the spread of disease enables healthcare providers to explain epidemics to patients more efficiently and to save much needed resources, too.
To find the real beginning of the modern use of maps in epidemiology, it’s necessary to travel all the way back to London in the mid-1850s. About this time there was a massive cholera outbreak that had killed 127 in three days. Within twelve days, the number had increased to 500.
John Snow, a local doctor, decided to hit the streets and track where the outbreak was coming from. He was able to map the locations of every person who had died as a result of cholera and he soon noticed a large cluster of deaths near a specific water pump. Ultimately, he determined that this was the source of contaminated water. Visualization was a very powerful tool in determining where the problem arose.
In today’s world, technology gives disease specialists a huge advantage. GIS programs enable epidemiologists to look at a location’s population demographics, access to healthcare, physical features, environmental factors, and more, all at once. Not only can this data be viewed spatially, but temporally as well.
GIS programming works essentially like a large database of information that can be tied to a map using a coordinate system. Individual data ‘layers,’ such as patient residences, treatment centers, or road lines, for example, are added to a base map. With only these three pieces of information, physicians can query how far away the average patient is from a treatment center. Typically, project-specific data is manually entered into Excel sheets that can be converted into a GIS layer while most open source data can be found in large GIS data clearinghouses. The system can hold and analyze hundreds of layers of data relatively quickly. With an experienced GIS specialist, useful maps can be produced shortly after project specific data has been collected and entered.
GIS allows doctors to draw conclusions that may not be as easy to see without data laid out visually, answering questions like ‘Is a certain demographic developing this illness?’ or ‘Have patients all been exposed to a specific chemical?’ Essentially, epidemiologists can run analyses to determine what certain patients have in common.
One case in which the spread of disease has been mapped successfully was during the 2014 Ebola outbreak. Geographic information systems were used to create many of the maps that enabled those covering the outbreak to speak about its severity in an understandable manner. A map produced by The World Health Organization and cited in a BBC report divides the countries of Western Africa into regions, outlining the growth of the problem as the disease spread between the months of March 2014 and November 2014.
Aside from providing a visual explanation of the severity of the spread of Ebola, these GIS maps also enabled doctors to predict avenues by which the outbreak was likely to spread. For instance, specialists were able to estimate how much time they had to prepare for outbreaks in new regions of the infected countries. Preparing in this manner enabled them to estimate the likelihood of specific villages being infected and to divide resources in a more efficient manner.
In many instances, geographic information systems are also used to more fully track and attempt to understand environmental factors that play a significant role in the development of a disease. An example of this is the Cancer Surveillance Program developed by the University of Southern California’s Public Health Program. The program works as a database in which doctors enter patient health and demographic data for all new cancer patients.
Because of the extent of the information within the database, researchers have found it to be an important tool from which to conduct large studies on possible causes of cancer. For instance, data collected in the GIS database has been used to show prostate cancer rates are increasing in areas of the Central Valley that have higher exposure to ambient pesticides. Researchers were able to compare past exposure rates and estimate current exposure rates based upon wind speed and direction. These estimates enable them to further research and monitor areas in which citizens might have a higher risk for developing prostate cancer and possibly influence pesticide use policies in the area.
Possibly the most advanced use of geographic information system software for disease monitoring and tracking is the Boston Children’s Hospital HealthMap. The map scans a number of large online information sources to determine where disease outbreaks are occurring all over the world. This advanced software allows professionals and normal citizens alike to use real-time data to determine where outbreaks are and how likely they are to become serious.
The map is so in tune with reliable new sources that it can track the extent of disease or virus reports to the nearest major city. Furthermore, it has been equipped with a number of predictive tools that help create a forecast of where illness is likely to take place. This is especially useful in estimating how hard the flu is likely to hit in a given area and how we should best attempt to prepare for it.
Disease mapping is a powerful tool that is starting to be utilized to a far greater extent than ever before. As seen with cancer research, GIS mapping software is allowing specialists to narrow down and target some of the potential causes of diseases. Epidemiologists are also able to track the spread of disease and visualize where it is likely to become a problem next. Additionally, predictive measures are allowing for greater preparation in potential disease outbreaks which ultimately ensures better use of already limited resources.
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