The World Health Organisation (WHO) will meet to decide whether the outbreak of a new coronavirus thought to have originated in eastern China should be labelled an international emergency.
Cases have also been found in Thailand, Japan, South Korea, the US, Vietnam, Singapore, Malaysia, Nepal, France, Australia and Canada.
Here's a look at the other times the international health body has declared an emergency.
The first recorded incident happened in April 2009, as the H1N1 virus spread around the world, killing more than 200,000 people.
Britain recorded 214 deaths, while 20 people died from swine flu in Ireland.
Initially travellers returning from Mexico, where the virus originated, were met by authorities at the airport and hygiene measures were recommended by the Health Protection Agency.
An increase in polio numbers in Pakistan, Afghanistan and Nigeria led to an emergency being declared in May 2014.
There has been no domestic cases of polio in the UK since 1982, with the disease virtually wiped out.
The deadly disease broke out in Guinea, Liberia and Sierra Leone, with an emergency declared from August 2014 to March 2016. Almost 30,000 people were infected and more than 11,000 died.
The UK made a significant contribution after the outbreak by working with the Wellcome Trust on an experimental vaccine which the European Medicines Agency approved to treat Ebola in November last year.
A vaccination programme is under way in the Democratic Republic of Congo’s (DRC) North Kivu province.
A second emergency was declared, after months of hesitation, last July after it was confirmed that Ebola had spread to Goma, the capital of North Kivu, where DRC’s international airport is located.
The Government said at the time that the Britain was “providing expertise and support” to help the WHO “in a very insecure region”.
The life-threatening virus was first identified in a monkey in Uganda in 1975.
Its spread by mosquitoes in the Americas led the WHO to declare it an emergency from February to November 2016.
The first emergency from a mosquito-borne disease is thought to have been responsible for 2,000 possible cases of birth defects and 29 infant deaths in Brazil.
The UK largely escaped the virus, with just two travel-associated cases confirmed in 2018.