Countries around the world are taking action to combat a new virus that has spread from China.
It is called a coronavirus because under a microscope it looks like lots of little crowns.
It was first spotted in the Chinese city of Wuhan and, like other coronaviruses, it originated in animals.
It is a respiratory virus which means it can affect people's breathing and lungs.
A vaccine is currently being developed and the public have been advised to not be panicked by the virus.
Those who were first infected either worked or shopped at the Huanan seafood wholesale market, which is located in the centre of Wuhan.
The lethal virus spread quickly, with other Chinese cities closing their public transport systems in a bid to try and stop it spreading further.
The outbreak coincided with the Chinese New Year, which was on January 25, and is China’s busiest travel season. The country extended its Lunar New Year holiday to February 9 while many schools remain closed.
Now, thousands of cases have been discovered abroad, due to people travelling on international flights without realising they were carrying the virus.
At time of writing there were no confirmed cases in Ireland.