Research team uses Google to predict disease outbreaks

Google reportedly processes an average of 40,000 searches every second, totaling billions each day. Now, researchers say it can also help track outbreaks and highlight the importance of vaccination programs through digital epidemiology.

The study, “Digital epidemiology reveals global childhood disease seasonality and the effects of immunization,” was published in the Proceedings of the National Academy of Sciences, and led by a team from the University of Michigan that combed through Google Trends data from 36 countries on 5 continents collected over an 11-year period starting in 2004. Although this technique has been used in the past to identify other types of outbreaks, the team’s study on chickenpox was the first to demonstrate the efficacy of a vaccine, according to Kevin Bakker, a doctoral student at the University of Michigan’s Department of Ecology and Evolutionary Biology.

“We were able to demonstrate that you can observe the reduction in clinical cases by noticing the reduction in Google searches by parents and children themselves. We 'ground-truthed' this with research showing a decrease in the number of cases during this same time period,” Bakker told Medical Economics. â€œBasically, the Google data were able to demonstrate a drastic reduction in chickenpox cases following mandated vaccination—meaning that the vaccine is highly effective at protecting both children and adults from chickenpox. Hopefully more countries will require the vaccine and chickenpox cases will drop across the globe.”

The research team says, through Google surveillance, they were able to predict the timing and magnitude of chickenpox outbreaks about a month in advance—a tool that could provide crucial time to prepare or track where further vaccination efforts are needed.

Larger disease surveillance programs focus on infectious diseases with high mortality, but less severe diseases—ones that can be easily prevented through vaccination, like chickenpox—can go unreported.

By observing the types of searches being conducted in an area, analysis can be performed that accurately predicts population-level diagnostic data. The report also revealed that countries with government-mandated vaccination programs had a significantly smaller number of queries, which the research team says demonstrates the efficacy of vaccination efforts in mitigating chickenpox outbreaks.

Searching the searches

The technique used by the team to track chickenpox—selected because of its distinct symptoms and scarce clinical case data—utilized searches performed by individuals seeking information on symptoms, diagnosis, treatment and vaccination against the disease. Researchers looked for spikes in search terms focusing on this information, and were able to match those to later outbreaks.

Reporting of chickenpox is typically low or non-existent in some areas, but by using Google, Bakker says the research team was able to confirm springtime outbreaks across the globe.

In the three countries that require reporting of chickenpox cases but not vaccination—Mexico, Thailand and Estonia—Google searches for “chickenpox” were strongly correlated to reported cases. The correlation was present, but weaker, in countries that vaccinate against chickenpox, like the U.S.

The data allowed researchers to create models to predict outbreaks, and revealed a reduction in chickenpox searches in countries with mandatory vaccination. For example, the team found that Germany, which increased its vaccination requirements beginning in 2004, there were marked drops in chickenpox searches as the years progressed and vaccination requirements became stricter.

"These results demonstrate that if you institute nationwide vaccination for chickenpox there is a very clear reduction in searches, which is a way to infer a strong reduction in total disease incidence," Bakker says.

This type of analysis not only demonstrates the importance of vaccination programs, but can also be applied to clinical practice, he says.

“Primary [care] physicians can ready themselves by being prepared for the increase in chickenpox-related issues—such as co-infection of the open wounds caused by chickenpox by streptococcus or staphylococcus bacteria,” Bakker says. â€œThese are the main causes of complications in chickenpox. In the U.S., this isn't as much of an issue, especially since chickenpox is fairly well reported here, but in most other countries data were unavailable, so we were able to show the 'peak' season of cases in 36 countries across 5 continents.”
Digital epidemiology could have diagnostic uses at other levels, as well. It could be used at the practice level if a physician had access to an individual’s internet search history, but it would likely take a team or a singular person devoted to studying patient search habits to work.

 â€œObviously it is always better to go see a doctor, but at least for initial, or perhaps chronic, symptoms where patients take time making an appointment, I think digital epidemiology can be an excellent data stream for both scientists and physicians.”