The World Health Organization will hold an emergency meeting Thursday on the yellow fever outbreak that has hit hardest in Angola but risks spreading further if vaccinations are not ramped up.

Such meetings from the UN agency are often held before the declaration of an international health emergency, as happened amid the Ebola outbreak in West Africa, and the current surge in neurological disorders linked to the spread of Zika virus in the Americas.

WHO spokesman Tarik Jasarevic told AFP the meeting had been called to underscore the severity of the yellow fever outbreak and to re-emphasise the need for mass vaccination against the viral disease.

As of May 12, Angola had reported 2,267 suspected yellow fever cases and 293 deaths in an outbreak that began in December and is most heavily concentrated in the capital Luanda.

The Democratic Republic of Congo has registered 44 suspected cases, both from a local outbreak and from patients who carried the virus from neighbouring Angola.

Eleven people have tested positive for yellow fever in China after returning from Angola, highlighting ‘the risk of international spread through non-immunised travellers,’ WHO has said.

Several cases have also been reported in Uganda.

The percentage of people immunised against yellow fever remains low in many parts of Africa, even though the vaccine is nearly 100 percent effective and relatively cheap.

WHO has sent 11.7 million doses to Angola and there are plans to vaccinate 2.2 million people in DR Congo.

WHO has pledged to beef up its emergency response systems after widespread criticism following the Ebola outbreak, with many experts saying it took the UN body far too long to sound a global alarm.