Amid the rapid spread of the novel coronavirus, Twitter is making it mandatory for its nearly 5,000 employees to work from home.

The social media company announced the decision on Wednesday after "strongly encouraging" its employees to work from home earlier this month.

"Our top priority remains the health and safety of our Tweeps, and we also have a responsibility to support our communities, those who are vulnerable, and the healthcare providers who are on the front lines of this pandemic," Jennifer Christie, Vice President, People at Twitter, wrote in a blog post.

"To continue this push, we are moving beyond our earlier guidance of 'strongly encouraging work from home' provided on March 2 and have now informed all employees globally they must work from home," she said.

The World Health Organisation (WHO) on Wednesday declared the Covid-19 outbreak a pandemic. The virus has spread globally, infecting over 118,000 people and killing more than 4,000. "We understand this is an unprecedented step, but these are unprecedented times," Christie said.

For contractors and hourly workers who are not able to perform their responsibilities from home, Twitter will continue to pay their labour costs to cover standard working hours while Twitter's work-from-home guidance and/or travel restrictions related to their assigned office are in effect, she added.

While Twitter has taken the "unprecedented step" of making work from home mandatory, a number of other companies including Google and Amazon have encouraged their employees in some areas hit by coronavirus to work from home.