Authorities across west Africa have announced a series of measures aimed at stopping the spread of the Ebola virus, which reached a fourth country last week with a death in Lagos, Africa's most populous city.

Nigeria closed and quarantined the hospital where a man died on Friday in the country's first recorded case of the deadly and highly contagious pathogen.

The closure of the clinic in one of the city's most densely populated districts came as police were called in to guard Sierra Leone's main Ebola treatment centre, while Liberia shut almost all its borders and banned public gatherings. Attempts to halt the seven month-crisis, which has spiralled into the world's biggest and most widespread outbreak of Ebola, have been hampered by a lack of resources and poor understanding in a region which has never experienced an epidemic.

Ebola has killed 672 people in Guinea, Liberia and Sierra Leone since it was first diagnosed in February. The pathogen is passed through contact with bodily fluids of infected patients or eating infected meat, and has no known cure, although chances of survival improve dramatically with early detection and treatment.

Medical staff put on their protective gear in Sierra Leone. Photograph: Reuters

"We have shut the hospital to enable us to properly quarantine the environment. Some of the hospital staff who were in close contact with the victim have been isolated," Lagos state health commissioner Jide Idris said during a press conference on Monday.

Authorities set up an isolation ward and began tracing those who had been in contact with Patrick Sawyer, a 40-year-old civil servant whose flight from his home in Monrovia, Liberia's capital, stopped over in Togo and Ghana. Some 60 contacts had been traced, including 44 health workers and 15 airport officials. Not all of the flight's passengers had been contacted as the airline had yet to provide a manifest, state officials said.

Derek Gatherer, a virologist at the University of Lancaster, said anyone on the plane near the infected man could be in "pretty serious danger".

"It depends on how much damage this traveller has already done," he said.

But he said Nigeria was richer than the other countries in the region, so could more easily mobilise resources to tackle an outbreak. "Nigerians have deep pockets and they can do as much as any western country could do if they have the motivation and organisation to get it done."

Liberian and Nigerian airports and seaports began screening international arrivals for Ebola symptoms, which can take up to 21 days to appear. Arik Air, a major carrier for the region, has suspended flights between Nigeria, Liberia and Sierra Leone, as travel peaks this week during the Muslim holiday of Eid.

Medical staff prepare to bring food to patients in Kailahun, Sierra Leone. Photograph: Reuters

Sawyer is believed to have contacted the virus from his sister, who died of Ebola earlier this month. But his travelling despite not feeling well has angered many.

"One of our compatriots met his untimely death and put to risk others across borders because of indiscipline and disrespect for the advice which had been given by health workers," Liberian president Ellen Johnson Sirleaf said during the country's independence day celebrations on Saturday.

She announced stringent new measures after two American volunteer doctors tested positive for Ebola, and the lead medical doctor at the country's largest hospital died. Samuel Brisbane had treated himself at home in an attempt not to infect other health workers, many of whom have been ostracised by their communities.

In Sierra Leone, where 454 have died, angry crowds gathered outside Kenema hospital in the country's remote east, where dozens are receiving treatment for the virus, and threatened to burn it down and remove the patients.

Lagos health commissioner Jide Idris, centre. Photograph: Pius Utomi Ekpei/AFP/Getty Images

The 1,000-strong crowd marched to the hospital after a former nurse told traders in a nearby fish market that "Ebola was unreal and a gimmick aimed at carrying out cannibalistic rituals", assistant inspector general Alfred Karrow-Kamara told Reuters.

Residents said police fired teargas to disperse the crowds and that a nine-year-old boy was shot in the leg by a police bullet.

Many communities have been left bewildered and angered by the deaths, and a belief that health workers living among the community are spreading the disease.

"It's not just superstition, it's just a scary situation for people there. Some of the reporting around it, that there is no treatment and that people bleed to death, may also discourage people from coming to hospital," said a researcher who spent time in Sierra Leone.

Others still live in denial. "I was one person that was saying the government was just playing tricks and want more money but now the way I see this thing killing people, I believe it," said Tenneh Fahnbulleh, a resident in Monrovia. The mother of three said her husband remained unconvinced even after a woman had died on their street in the past week.