The Liberian government has closed most of the West African nation's border crossings and introduced stringent health measures in a bid to curb the world's deadliest-ever outbreak of Ebola.
Meanwhile, one of Liberia's most high-profile doctors has died of Ebola, officials said Sunday (local time), and an American physician was being treated for the deadly virus, highlighting the risks facing health workers trying to combat an outbreak that has killed more than 670 people in West Africa - the largest ever recorded.
In Liberia's capital of Monrovia, President Ellen Johnson Sirleaf said the government is doing everything to fight the virus including inspecting and testing all outgoing and incoming passengers by Liberia's airport authority.
''All borders of Liberia will be closed with the exception of major entry points. At these entry points, preventive and testing centres will be established, and stringent preventive measures to be announced will be scrupulously adhered to,'' she said.
Ebola can kill up to 90 per cent of those who catch it, although the fatality rate of the current outbreak is around 60 percent. Highly contagious, especially in the late stages, its symptoms include vomiting and diarrhoea as well as internal and external bleeding.
Under the new measures, public gatherings such as marches, demonstrations and promotional advertisements also will be restricted.
Despite efforts to fight the disease, the virus continues to spread.
Dr Samuel Brisbane, a top Liberian health official, was treating Ebola patients at the country's largest hospital, the John F. Kennedy Memorial Medical Center in Monrovia, when he fell ill. He died Saturday, said Tolbert Nyenswah, an assistant health minister. A Ugandan doctor died earlier this month.
A 33-year-old American doctor working for relief organisation Samaritan's Purse in Liberia tested positive for the disease on Saturday.
The American physician, 33-year-old Dr Kent Brantly, was in Liberia helping to respond to the outbreak that has killed 129 people nationwide when he fell ill, according to the North Carolina-based medical charity, Samaritan's Purse.
He was receiving intensive medical care in a Monrovia hospital and was in stable condition, according to a spokeswoman for the aid group, Melissa Strickland.
''We are hopeful, but he is certainly not out of the woods yet,'' she said.Early treatment improves a patient's chances of survival, and Brantly recognised his own symptoms and began receiving care immediately, Strickland said.
A second American, a missionary working in the Liberian capital, was also taken ill and was being treated in isolation there, said the pastor of a North Carolina church that sponsored her work.
Nancy Writebol was gravely ill and in isolation in Monrovia, her husband, David, told a church elder via Skype, according to the Reverend John Munro, pastor of Calvary Church in Charlotte, North Carolina.
Munro said the couple, who had been in Liberia for about a year, insisted on staying there despite the Ebola threat. ''These are real heroes - people who do things quietly behind the scenes, people with a very strong vocation and very strong faith,'' Munro said.
SPREADS TO LAGOS
Ominously, Nigerian authorities said on Friday that a Liberian man died of Ebola after flying from Monrovia to Lagos via Lome, Togo. The case underscored the difficulty of preventing Ebola victims from travelling given weak screening systems and the fact that the initial symptoms of the disease - including fever and sore throat - resemble many other illnesses.
Health workers are among those at greatest risk of contracting the disease, which spreads through contact with bodily fluids.
Photos of Brantly working in Liberia show him swathed head-to-toe in white protective coveralls, gloves and a head-and-face mask that he wore for hours a day while treating Ebola patients.
Earlier this year, the American was quoted in a posting about the dangers facing health workers trying to contain the disease. ''In past Ebola outbreaks, many of the casualties have been health care workers who contracted the disease through their work caring for infected individuals,'' he said.
There is no known cure for Ebola, which begins with symptoms including fever and sore throat and escalates to vomiting, diarrhoea and internal and external bleeding.
At least 1201 people have been infected in Liberia, Sierra Leone and Guinea, according to the World Health Organization, and 672 have died. Besides the Liberian fatalities, 319 people have died in Guinea and 224 in Sierra Leone.
The WHO says the disease is not contagious until a person begins to show symptoms. Brantly's wife and children had been living with him in Liberia but flew home to the US about a week ago, before the doctor started showing any signs of illness, Strickland said.
''They have absolutely shown no symptoms,'' she said.
Besides Brantly and the two doctors in Liberia, Sierra Leone's top Ebola doctor and a doctor in Liberia's central Bong County have also fallen ill.
The situation ''is getting more and more scary,'' said Nyenswah, the country's assistant health minister.
Meanwhile, the fact that a sick Liberian could board a flight to Nigeria raised new fears that other passengers could take the disease beyond Africa.
An outbreak in Lagos, a megacity where many lived in cramped conditions, could be a major public health disaster.
The West Africa outbreak is believed to have begun as far back as January in southeast Guinea, though the first cases weren't confirmed until March.