On-line Activities Indicate Increasing Flu Trend.

Swedish bloggers and tweeters are increasingly chattering about the seasonal influenza (also covered in an earlier blog post). The trend of the flu signals captured by the Ethersource barometer is clearly on the rise. This should come as no surprise since we are, in fact, looking at the seasonal flu. The interesting thing here is how well the barometer reflects what is reported by the Swedish Institute for Communicable Disease Control (SMI) in their weekly reports. Those reports are based on input from sentinels and laboratories, and by necessity, they lag behind in time: the current report is for the period of February 6 – 13, which is a week old by now.

Of the approximately 80 000 social media posts that matched our criteria for being included in the barometer on a given day in the period depicted in the image below, only a small fraction concern the flu. The flu isn’t contagious via the web, but information is. Keep your eyes open, and report symptoms to influenzanet to allow scientists to better stay on top of the flu spreading throughout Sweden.

Meanwhile, as we keep our eyes open for the spring sun, we’ll make sure to monitor the flu barometer and take note of any declining trends. We’ll keep you posted.

People active in Swedish social media are increasingly concerned about the seasonal influenza. The image shows a seven day moving average for the past two months of the influenza signal. The annotations in the graph is the Ethersource anomaly detection algorithms at work: each flag indicate a point in time where the change in trend warranted our attention.

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Real-time Syndromic Surveillance of Social Media for Disease Symptoms related to Seasonal Influenza

We do real-time monitoring of social media for disease symptoms
there is still no evidence of an outbreak of the seasonal flu in Sweden
we observe, however, an increasing trend in the intensity of symptoms

The inevitable influenza season will soon come knocking on our doors. How do we know when it has started, and how do we know just how severe it is? To this end, there are on-line tools for syndromic surveillance, aiding individual medical practitioners and national disease control centers alike to combat the spread of influenza. Internationally, perhaps the most well-known monitoring service is Google Flu Trends. Nationally, Influensakoll keeps track of the current state of flu-related illness in Sweden. Along the same lines, research carried out at the Swedish Institute for Infectious Disease Control (SMI) show the feasibility of using search queries submitted to the medical web site Vårdguiden for outbreak detection and monitoring. SMI also publishes weekly influenza reports based on input from labs and sentinels.

In addition, there is a growing effort in the research community of mining on-line social media, mostly Twitter, in English, and only by using keywords with the purpose of facilitating early-warning and outbreak detection to be used by health authorities in their planning and conducting targeted counter-measures to epidemic diseases. Another interesting approach is that taken by the Iowa Electronic Health Market which is a prediction market for syndromic surveillance.

While the above mentioned services and research rely on either active participation on behalf of the users, or on keyword matching in social media feeds with the purpose of finding patterns, we’ve taken a different route to finding out the state of illness of Sweden. We’ve enhanced the barometer introduced earlier with concepts (not keywords) corresponding to a range of disease symptoms such as migraine, fever, expectorate, headache, nausea, sore throat, and head cold, facilitating the triangulation of more complex illnesses without having to wait for the bloggers, tweeters, forum participants, and facebookers out there to become so ill that they either actively seek answers related to their health condition, or start communicating using the actual name of the disease.

Our approach attempts to catch signs of illness early on, expressed as the participants in social media do what they usually do, that is, communicate with their peers. By focusing on the symptoms, we believe it is possible to get an early-warning of the seasonal flu, before anyone realizes it is what they are actually talking about. The image below illustrates the discrepancy between the score for the concept of influenza (the green, nearly flat line at the bottom of the graph) and the scores for some of the symptoms of influenza; expectoration (blue line), headache (red line), and fever (yellow line). Clearly, people have not yet experienced the flu strongly enough to talk about it, although they talk loudly about some of its symptoms. Note that the graph reveals an increasing trend in the intensity of the symptoms! The Ethersource-based barometer thus serves as a complement to other surveillance tools in that it picks up on trends of (combinations of) symptoms earlier.

Expressions of the concepts expectoration, headache, fever, and influenza in Swedish social media, early December 2011. Note that while the influenza score is constantly low, the other three symptoms vary with the time-of-day, taking precedence over each other in various ways.

Gavagai’s Ethersource technology allows for the kind of syndromic surveillance of disease symptoms described in this blog post to be carried out in real-time, in any language.

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How are you Sweden? Happier AND more uncertain during weekends.

We’re using Ethersource to monitor the mood of the Swedish blogosphere in terms of positivity, negativity, uncertainty, and an index we call Positivity Propensity Index (PPI).

The graphs below show two particularly interesting things.

Positivity (as in PPI) is cyclic on a weekly basis; Swedes are happier during weekends (Image 1). We all knew this, but it’s good to get it on ink.
At the same time, Swedes are more uncertain during Fridays, Saturdays, and Sundays, than they are during the rest of the week (Image 2).

Image 1 shows the positivity, negativity, and PPI for a three week period in 2011. Note the rise in PPI and the decline in absolute positivity and negativity during the weekends (red circles). The decline is a direct result of people blogging less during weekends, especially during weekends with good weather, as was the one on October 1-2. The rise in PPI (blue curve) indicates that people are, in fact, saying kinder things and being more positive.

Image 1: The positivity, negativity, and PPI in the Swedish blogosphere, September 22 through October 11, 2011.

Image 2 shows the uncertainty (labelled IFFY), positivity, and negativity for the weekend October 7 – 9, 2011. The graph clearly shows the early onset of uncertainty compared to those of positivity and negativity. It also gives away that uncertainty is relatively high during weekends. The same patterns holds for the weekends we’ve seen so far. Upon inspecting some of the blog posts underlying the uncertainty curve, it is evident that us Swedes are prone to ponder the big questions in life during the dark hours of the weekends.

Image 2: The expressed uncertainty during weekends is high, and the onset precedes that of the rise in positivity and negativity.

We’ll continue to monitor the Swedish blogosphere and look for other interesting bits of information. For instance, is the pattern of rise in PPI during weekends more pronounced during a particular time of the year? Do we express more uncertainty in the face of Christmas?

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