The world’s worst Ebola outbreak is sweeping through West Africa, where 729 people have already died of the deadly virus since late March.
The US has issued an advisory against nonessential travel to the three worst affected countries -- Guinea, Sierra Leone and Liberia -- which have reported 1,322 cases.
Sierra Leone has declared the Ebola outbreak a public health emergency and called in troops to help contain the virus.
Nigeria became the tipping point this week as it was the first case of the virus going out of the three countries where the outbreak started.
The Nigeria case made the world sit up to the threat of the virus travelling out of Africa and causing outbreaks across continents. Swine flu or H1N1 did exactly that, spreading across the world within a few months and turning into a pandemic.
"Ebola is worsening in West Africa," said Thomas Frieden, director of the Centers for Disease Control and Prevention (CDC), announcing its strongest level 3 advisory to these countries on Thursday.
“CDC, along with others, is surging to begin to turn the tide. It is not going to be quick. It is not going to be easy. But we know what to do. The current outbreak is bad. It’s the biggest, the most complex, and the first time it’s been present in this region,” he said.
The shared border of Guinea, Sierra Leone and Liberia is the epicentre of the outbreak, said the CDC.
India is reviewing the situation to assess whether there is need for a travel warning against affected nations.
Ebola is a highly-contagious haemorrhagic virus that breaks down the epithelial cell wall of blood vessels to trigger extensive internal and external bleeding. Initial symptoms include sudden onset of fever, muscle pain, weakness, headaches, a sore throat, vomiting and diarrhoea. As the infection worsens, external and internal bleeding causes those infected to die from shock.
There are no effective drugs or vaccines to treat the virus that has killed more than 60% of those infected in the current outbreak.
Infection spreads through body fluids and can the can spread even after death, which necessitates decontamination and treatment in isolation wards.
The best way to control the disease is using traditional public health measures, such as identifying those who are sick, tracking down everyone they could have exposed, monitoring them during a 21-day "fever watch" to spot early symptoms, then treating people in isolation until they are no longer contagious.
Nigeria has put 69 people under surveillance following the death of a passenger travelling from Liberia to Nigeria on Asky Airline on Thursday.
The World Health Organisation announced a US$100 million response plan to the outbreak, which killed 57 people over four days leading to July 27 in the four West African countries.
On Thursday, two American health-workers infected with the Ebola virus in West Africa were taken to the US for treatment.
The World Health Organisation said it would launch a $100 million response plan on Friday during a meeting with the affected nations in Guinea. It is in urgent talks with donors and international agencies to send more medical staff and resources to the region, it said.
Watch video: US warns against traveling to Ebola-hit areas