LONDON - Fears that the West African Ebola outbreak could spread to other continents are growing, with European and Asian countries on alert.
This comes after the virus crossed borders for the first time by plane and a 40-year-old man who had travelled from Liberia died in Nigeria - the country's first death from Ebola.
Medical charity Medecins Sans Frontieres said that the crisis gripping Guinea, Liberia and Sierra Leone would only get worse and warned that there was no overarching strategy to handle the world's worst outbreak of the disease.
The International Civil Aviation Organisation (ICAO) has held talks with global health officials on potential measures to halt the spread of the virus.
Sierra Leone's president has declared a public health emergency, saying that the epicentres of the outbreak would be quarantined and asked the security forces to enforce the measures.
The United Nations says more than 720 people in West Africa have died of Ebola since February - 233 of them in Sierra Leone.
They include Dr Sheik Umar Khan, who led Sierra Leone's fight against the virus.
Guinea is the worst-hit, with 339 dead.
In Hong Kong, a densely populated city previously scarred by disease outbreaks such as the 2003 Sars epidemic, health officials confirmed they would quarantine, as a precautionary measure, any visitor from Guinea, Sierra Leone and Liberia who showed fever symptoms.
One woman arriving in the city from Africa, who showed symptoms including fever and vomiting, has tested negative for Ebola.
In Britain, where one person has tested negative for the disease, Foreign Secretary Philip Hammond said it was regarded as "a very serious threat".
Togo-based pan-African airline ASKY, which serves 20 destinations, on Tuesday halted all flights to and from Liberia and Sierra Leone. ASKY was the airline that had carried the infected passenger to Nigeria.
The virus crossing borders for the first time by plane could lead to new flight restrictions aimed at containing outbreaks, the world aviation agency said.
"Until now (the virus) had not impacted commercial aviation, but now we're affected," ICAO secretary-general Raymond Benjamin said.
Singapore's Ministry of Health said Singaporeans should not be alarmed by the reports.
"Ebola poses a low public-health risk to Singapore since person-to-person transmission results from direct contact with bodily fluids of those infected, and there is low travel connectivity to West Africa, where the current outbreak remains limited to," it said in an advisory.
Meanwhile, the Thai health authorities said they had ordered all hospitals to monitor patients for symptoms, particularly nationals or foreign tourists who had been in the outbreak area.
Ebola can kill victims within days. It causes severe fever and muscle pain, vomiting, diarrhoea and, in some cases, organ failure and unstoppable bleeding.
Benjamin Black, a British doctor volunteering in Sierra Leone, told Metro newspaper that the medical staff were swamped.