Alarm has risen further in west Africa over the deadliest outbreak yet of the Ebola virus, with a top Liberian doctor succumbing to the disease, an American doctor and a missionary in the country contracting it and Sierra Leone's capital, Freetown, seeing its first fatal case.
Late on Sunday Liberia announced the closure all but three land border crossings, restricted public gatherings and quarantined communities heavily affected.
Meanwhile, concern rose over the case of a man who flew from Liberia to Nigeria last week but collapsed when he left the plane and later died of Ebola.
The situation "is getting more and more scary", said Tolbert Nyenswah, Liberia's assistant health minister.
Samaritan's Purse, a Christian charity, said the doctor infected, Kent Brantly, was in stable condition and had been isolated at the group's Ebola treatment centre at the ELWA Hospital in the Liberian capital, Monrovia.
Nancy Writebol, a missionary with the SIM Christian charity that runs the hospital, was also in stable condition, according to Samaritan's Purse.
"They're both receiving intensive early treatment, but certainly it's a dangerous situation and a frightening situation," spokeswoman Melissa Strickland said.
Early treatment was key to recovery from the potentially deadly disease, she added.
Writebol had been working as a hygienist responsible for detoxifying protective suits worn by those entering and exiting an Ebola isolation centre.
Watch: What is Ebola virus?
On Saturday, Dr Samuel Brisbane, who had been treating Ebola patients at Liberia's largest hospital, died of the disease.
Health workers are among those at greatest risk of contracting the disease, which spreads via contact with bodily fluids.
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 current Ebola epidemic has killed at least 660 people in four west African countries since the start of the year, according to the World Health Organisation.
At the weekend, a woman suffering from the first confirmed case of Ebola in Sierra Leone's capital died after her parents forcibly removed her from hospital.
Saudatu Koroma, a 32-year-old trainee hairdresser, was admitted to a clinic on July 23 and tested positive for the disease. She died on Saturday while on her way back to hospital.
The house where the dead woman had lived in Freetown has been quarantined with the other residents for 21 days.
Koroma's was the first case of Ebola to reach Freetown, and came days after the disease spread to another major city, Lagos, when a Liberian official flew there via Togo.
The official, a 40-year-old, died at a private hospital after collapsing at Lagos international airport.
The fact that the official, Patrick Sawyer, was able to board an international flight despite being ill raised fears that the disease could spread beyond the four countries so far affected.
"He could have gone anywhere" on a flight, said Ben Neuman, a virologist at the University of Reading in the U.K. "As this epidemic goes on, this sort of thing is eventually probably going to happen."
Nigeria's international airports are screening passengers arriving from foreign countries, and health officials are working with ports and land borders to raise awareness of the disease. Togo's government also said it was on high alert.
Nigerian airline Arik said it was halting direct flights to Liberia and Sierra Leone.
An outbreak in Lagos, a megacity where many lived in cramped conditions, could be a major public health disaster.
Ebola can fell victims within days, causing severe fever and muscle pain, vomiting, diarrhoea and, in some cases, organ failure and unstoppable bleeding.
People can catch it from touching an infected person.
Additional reporting by Associated Press, Bloomberg