Twitter (https://twitter.com/home) is a microblogging and social network service where users can post messages of up to 280 characters. These can be interacted with by likes, replies, retweets and citations. Users can follow each other without mandatory reciprocity, to determine which content they want to see.

COVID-19 is the disease caused by a new coronavirus called SARS-CoV-2. World Health Organisation (WHO) first learned of this new virus on 31 December 2019, following a report of a cluster of cases of 'viral pneumonia' in Wuhan, People's Republic of China. The WHO declared the outbreak as a pandemic in March 2020. Globally, as of 5:02pm CET, 23 November 2020, there have been 58.425.681 confirmed cases of COVID-19, including 1.385.218 deaths, reported to WHO. (https://www.who.int/)

A social network structure is created when connections ('edges', 'links', 'ties', 'contacts') are created among social actors ('nodes', 'vertices', 'actors'), such as individuals and organizations [1]. It is based on mathematical concepts of graph theory that provides tools and characteristics to analyse those structures.

Sentiment analysis, also called opinion mining, is the field of study that analyzes people’s opinions, sentiments, evaluations, appraisals, attitudes, and emotions towards entities such as products, services, organizations, individuals, issues, events, topics, and their attributes. It uses natural language processing, linguistics and text analysis. Sentiment analysis has been mainly investigated at document level, sentence level or entity and aspect level. [2]

The term 'fake news' has no aggreed on definition, so there are multiple of them that include or exclude certain 'news'. Here a list of some definitions:

• „News articles that are intentionally and verifiably false, and could mislead readers.“ [3]
• „Fake news is a news article that is intentionally and verifiably false.“ [4]
• „… online publication of intentionally or knowingly false statements of fact.“ [5]

[1] Wasserman, S., & Faust, K. (1994). Social Network Analysis: Methods and Applications (Structural Analysis in the Social Sciences). Cambridge: Cambridge University Press. doi:10.1017/CBO9780511815478

[2] Liu, B. (2012). Sentiment analysis and opinion mining. Synthesis lectures on human language technologies, 5(1), 1-167.

[3] Allcott, H., & Gentzkow, M. (2017). Social media and fake news in the 2016 election. Journal of economic perspectives, 31(2), 211-36.

[4] Shu, K., Sliva, A., Wang, S., Tang, J., & Liu, H. (2017). Fake news detection on social media: A data mining perspective. ACM SIGKDD explorations newsletter, 19(1), 22-36.

[5] Klein, D., & Wueller, J. (2017). Fake news: A legal perspective. Journal of Internet Law (Apr. 2017).