A long-running, wildly popular game that simulates a worldwide pandemic was just pulled from Apple's iPhone app store in China.

The game's use spiked in China after the coronavirus outbreak, and it reached the top spot on Apple's App Store charts as a result.

The game's maker says it doesn't know why the game was pulled. "It's not clear to us if this removal is linked to the ongoing coronavirus outbreak that China is facing," a statement from Ndemic Creations says.

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A wildly popular game that intends to simulate a worldwide epidemic recently had a cosmic surge in popularity — "Plague Inc.," as it's known, even became the most popular game on Apple's iPhone app store around the world.

Recently, the game topped Apple's app store chart in China. That's particularly notable because of the ongoing coronavirus outbreak, which originated in and has mostly affected China, where more than 78,000 people have been sickened.

As of Thursday, though, the app was pulled from China's iPhone app store.

The game's creator, Ndemic Creations, said the game was pulled citing "content that is illegal in China as determined by the Cyberspace Administration of China."

"Plague Inc" Ndemic Creations

The game's popularity recently spiked amid the ongoing coronavirus outbreak, but its creators aren't sure if the game being pulled from China's app store has anything to do with that connection.

"It's not clear to us if this removal is linked to the ongoing coronavirus outbreak that China is facing," a statement published by the studio on Thursday morning said. "However, Plague Inc.'s educational importance has been repeatedly recognised by organisations like the CDC and we are currently working with major global health organisations to determine how we can best support their efforts to contain and control COVID-19."

As of Thursday, the death toll of the coronavirus outbreak has reached 2,810, with more than 82,000 people infected worldwide most of them in China.

Since "Plague Inc." was released eight years ago, it has seen occasional spikes in popularity associated with health scares.

"Whenever there is an outbreak of disease we see an increase in players, as people seek to find out more about how diseases spread and to understand the complexities of viral outbreaks," the studio said in late January. "However, please remember that 'Plague Inc.' is a game, not a scientific model and that the current coronavirus outbreak is a very real situation which is impacting a huge number of people. We would always recommend that players get their information directly from local and global health authorities."