The World Health Organisation (WHO) is meeting in Geneva to discuss whether the Zika virus outbreak should be declared a global health emergency.
Monday's meeting comes after warnings by the UN health agency that the mosquito-borne virus, which is strongly suspected of causing birth defects, was "spreading explosively" in the Americas - WHO is expecting up to four million cases in the region this year.
Q&A: All you need to know about Zika
Senior WHO officials, joined by representatives of affected countries and experts from around the globe, will meet behind closed doors to determine if Zika should be considered a "public health emergency of international concern".
Tarik Jasarevic, a WHO spokesman, said that the meeting "will look really into what we know and will also see what level of health emergency this represents".
A decision is not to be made public until Tuesday at the earliest.
WHO under pressure
WHO is under pressure to act quickly in the fight against Zika, after admitting it was slow to respond to the recent Ebola outbreak that ravaged parts of West Africa and killed more than 11,000 people.
Zika virus is a mosquito-transmitted infection related to dengue, yellow fever and West Nile virus. Symptoms are mild and include fever, rashes and joint pain.
Yet, the disease is "strongly suspected' to be linked to microcephaly, a birth defect characterised by incomplete brain development and an unusually small head.
Brazil is the hardest-hit country and sounded the alarm in October, when a rash of microcephaly cases emerged in the northeast.
Since then, there have been 270 confirmed cases of microcephaly and 3,448 suspected cases.
READ MORE: Mosquito-borne Zika virus 'spreading explosively'
A number of countries, including Colombia, Ecuador, El Salvador, Jamaica and Puerto Rico, have warned women to delay pregnancies until the Zika outbreak is brought under control amid worries over the recent surge in cases.
Worries over Zika have spread beyond the affected areas to Europe and North America, where dozens of cases have been identified among people returning from vacation or business abroad.
There is no vaccine or specific medicine currently available and treatment is normally focused on relieving the symptoms. Research is being done to develop a rapid test which could look for antibodies after a patient has recovered from the virus, making it possible to test for immunity.
Only one in five people infected becomes ill, while treatment in hospital is uncommon and deaths are rare.
Source: Al Jazeera and agencies