Influencers and Contagion in Social Medias


The word “contagion” has its origin from around the 14th century, from Old French (contagion) and Latin (contagionem), which means “a touching, contact, contagion” (Harper, 2010). Nowadays, the word “contagion” could be used to explain “the communication of disease by direct or indirect contact”, or also in the context of an emotion, as of spreading an idea: “a contagion of fear” (Random House Inc, 2017).

Broader Usage

“Contagion” is commonly used when for instance talking about viruses spreading in mammals. It could also be used regarding the spread of emotions or feelings in networks, and not just as a physical thing where a virus infiltrates cells to make more viruses, spreading from one host to another. The concept of contagion on an emotional level is said to participate in social networks, where an idea or emotion can take form and spread throughout the network. “Data from a 20-years longitudinal study suggest that emotions can be passed via social networks, and have long-term effects” (Ferrara E. and Yang Z., 2015). Resulting in an idea or emotion adopted by others to sustain in individuals. “The possibility to manipulate the information that users see is clearly well suited to address questions about the existence and magnitude of emotional contagion” (Ferrara E. and Yang Z., 2015).

Studies and Controversy

However, as Collins states in his text about “How ‘contagion’ became contagious”, an offbeat study done by Christakis and Fowler in 2007 argued that everything from obesity to sexual orientation could spread from person to person in much the same way as a virus (Collins, 2014). This were immediately mediated whether the virus metaphor mentioned above was taken too far. Some viewed the idea as completely absurd, while others followed their study. Mainly what researchers disagree on, according to Collins, is the explanation of contagion, whether it is “one person’s obesity actually causes another’s. Or it could be that there’s some other variable, something that explains why those most likely to gain weight are also most likely to become friends” (2014).


In 2010, Shalizi and Thomas proved that it is impossible to tell the difference between what is contagion and a second explanation called homophily. Homophily could be explained as the tendency of individuals to associate and bond with similar others. Another study done by Greg Ver Steeg and Aram Galstyan, states that the patterns seen in the networks might have to do with quantum theory. Their findings stated that homophily alone could not explain what was seen in the earlier research regarding the well discussed virus metaphor and obesity claim. There must be another variable taking place (Collins, 2014; Steeg V., Greg and Aram Galstyan, 2013).

Social Media and Influencers

Instagram, a large photo-sharing service and social network, has 500M+ daily active users (Instagram-press, 2017), where some of the users have more than 100M followers which is an enormous amount of followers. Today, it is quite easy to become an influencer on Instagram. An influencer is a person of interest to others, either it is in the category of makeup, fitness, cooking, photographing or other. Marketing firms and brands have an interest in influencers in the way of using them to write reviews or test their products in order to sell their products. This is done through an individual influencer, rather than targeting the market as a whole. Celebrities and other influential people with high credibility (note: many followers) contributes in selling a product or service. In return, the influencers either get to test a product or service for free, or get money from it by for example affiliate links. Affiliate marketing gives its affiliates’ a certain amount of money based on visitors or customers that is given to the firm.


The affiliate market and influencers could be a small (still important) part of the whole contagion concept. Political views and other strongly formed ideas could easily influence people exposed to or dwelling in the same groups or networks. In a negative direction, influencers could in a way help to contaminate social networks and followers to either feel a certain way, or stand by a given product or subject. Whether the spread of ideas, products and emotions occurs due to social contagion is hard to figure out as the listed studies in this text shows. Instead, what Collins discusses in his text; that ideas, products and emotions are broadcasted on us rather than necessarily spreading from person to person like a virus.



Collins, Nathan. 2014. “How ‘contagion’ became contagious”. Pacific Standard. Accessed: 15.11.17. 2017. “Contagion”. Random House, Inc. Accessed: 13.11.17. 

Ferrara, Emilio and Zeyao Yang. 2015. “Measuring Emotional Contagion in Social Media”. Plos. Accessed: 15.11.17.

Harper, Douglas. 2010. “Contagion”. Online Etymology Dictionary. Accessed: 13.11.17.

Instagram Press. 2017. “Our Story”. Instagram. Accessed: 15.11.17.

Steeg, Greg Ver and Aram Galstyan. 2013. “Statistical Test for Contagion in Observational Social Network Studies”. Cornell University Library. Accessed: 15.11.17.