Issue 13 / 15 April 2013

METAPHORS for the spread of information in our digital age often draw on the language of infectious disease: when an idea really takes off in cyberspace, we say it has gone viral.

But what happens when the subject of online interactions is communicable disease itself, or health more broadly?

Researchers from Penn State University in the US set out to examine the spread of opinions about a new vaccine against H1N1 influenza on social network Twitter.

“The rapid worldwide adoption of online social network services means that an increasing fraction of (mis-)information diffusion is occurring on these networks”, they wrote in the journal, EPJ Data Science, this month.

A quasi-epidemiological study of more than 300 000 tweets led them to conclude “a standard contagion framework” might not be adequate for understanding the spread of health-related sentiments online.

They defined such a framework as “the conceptual idea that increased exposure to any given agent (whether biological or social) will lead to an increased transmission — and predict an increased adoption — of that agent”.

Opinions, in other words, don’t operate in the same way as microbiological agents.

Some opinions anyway. Exposure to negative sentiment was found to be, in the researchers’ words, “contagious”: people exposed to negative tweets about the vaccine were more likely to express negative views themselves.

Not that surprising, perhaps. Disturbingly, though, a similar effect was not found when the messages were positive. In fact, exposure to positive messages about the vaccine also seemed to increase the likelihood that an individual would express a negative opinion.

So, if expressing a negative opinion sparks more negative opinions, and expressing a positive opinion also sparks more negative opinions, where does that leave online public health campaigns? Or indeed, public health campaigns of any kind?

Should everybody just shut up and leave people to get on with it?

Of course, this study doesn’t provide enough information to be making that kind of judgement but it does raise interesting questions.

The efficacy of campaigns designed to tackle issues as diverse as smoking, diet and road safety has long been debated, given that clear cause-and-effect data isn’t really obtainable.

Do ads designed to get us to eat more vegetables or quit smoking actually work?

These researchers suggest public health campaigns might benefit from a shift away from issuing positive messages and towards preventing negative ones, assuming further research confirms their findings.

Easier said than done, of course. I wonder if we’ll ever be able to prevent fabrication of wild conspiracy theories about vaccines.

What this study does point to is a huge, and largely untapped, potential to understand how opinions and feelings about health spread and how they might affect behaviour.

Interactions on a social network site don’t necessarily replicate those that happen in other contexts (and expressed opinions don’t necessarily reflect actual health behaviours either) but the public nature of Twitter gives it enormous value from a research point of view.

For the first time, we can watch — and pick apart — the way a message spreads, whether it’s a scientific finding, unsubstantiated rumour or downright lie.

Social media may not just be a tool for getting a message out there, but also a means to better understand how beliefs spread across populations and how that affects the decisions we all make about our health.

Jane McCredie is a Sydney-based science and medicine writer.

Posted 15 April 2013

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