A game developers conference in San Francisco was postponed Friday, after Facebook and Microsoft withdrew from the event due to concerns about the spread of novel coronavirus. The annual gathering was due to start March 16 in a downtown convention center but will be held later this year instead, the organizers of the Game Developers Conference said. It joins a growing list of global events that have been nixed as the virus spreads around the world. US officials on Friday reported a fourth infection with unknown origin - including two in California - fuelling fears the epidemic was spreading in the country where more than 60 cases have been confirmed.

Facebook this week canceled its F8 developers conference, the biggest annual event for the US tech giant, due to virus worries.

The gathering in the Silicon Valley city of San Jose typically draws thousands of software makers from around the world who collaborate with the tech giant on its platform.

Face-to-face interaction at San Jose conference center will be replaced with online presentations.