Colleagues from over 20 countries will tweet to demonstrate local initiatives and support World MS Day #MSday24 pic.twitter.com/0oexqc21mv

— Merck (@merckgroup) May 25, 2016

Merck is holding a global 'tweet-a-thon' as part of its activities for World MS Day, with today's initiative set to involve employees from over 20 countries.

The German pharma company began by handing its @Merckgroup Twitter account over to its Australian team, subsequently passing the baton to employees in countries such as Russia, South Africa, Poland and Greece.

Set up in 2009 by the Multiple Sclerosis International Federation (MSIF) and its members, World MS Day brings the global MS community together to share stories, raise awareness and campaign on behalf of those affected.

Some 2.3 million people around the world are estimated to be affected by multiple sclerosis and this year's campaign theme is 'independence'.