The World Health Organization (WHO) has announced that the coronavirus outbreak is officially a pandemic... but what is a pandemic?
Eight countries are now each reporting more than 1,000 cases of COVID-19, caused by the virus that has infected more than 120,000 people worldwide.
But what exactly is a pandemic? What does declaring one mean? And how are they dealt with?
The word 'pandemic' might sound a bit scary - but pandemics can be controlled.
Here's what you need to know.
A pandemic is when an infectious disease spreads easily from person to person in lots of parts of the world.
It's different to an epidemic - that's when an unusually large number of people in a smaller area get a disease at the same time.
So a pandemic is when an epidemic spreads across the world.
When the WHO declares a pandemic, it leads to a huge co-ordinated effort between countries and scientists all over the world. Money and resources like medicines are used in a really organised and targeted way to try to stop the pandemic as soon as possible.
The WHO's goal is "the highest level of health" for "all peoples". So when it makes these declarations it is all about helping people to get better.
Pandemic control can lead to countries and governments working closely together, people getting extra vaccinations when appropriate, asking people to stay at home, stopping people from gathering together in big groups or from travelling for a period of time, and making sure that instructions are communicated clearly so people know what to do.
A pandemic is more about how far a disease has spread, rather than how severe the disease is.
There have been lots of pandemics that have been controlled.
Some of the biggest examples in history have been the HIV/AIDS pandemic and the bird flu pandemic in 2009.
Pandemics don't last forever, and there are different reasons for that - including the amount of co-ordinated effort that is used to shut them down.
Other reasons include people becoming more immune to the disease, and it starts to affect fewer and fewer people.
Or if the disease is carried by animals, these animals might become inactive.
An example of this is malaria - it's transmitted by mosquitoes and they become inactive during cold weather or winter.