Image copyright Reuters Image caption Health workers are battling to contain the deadliest outbreak of Ebola 
 
 A major West African airline has stopped flying to Liberia and Sierra Leone amid growing concern about the spread of the deadly Ebola virus. 
 
 Asky said it took the decision to keep "its passengers and staff safe during this unsettling time". 
 
 The number of people killed by the virus in West Africa has now reached 672, according to new UN figures. 
 
 In Sierra Leone, the doctor who led the fight against Ebola, Sheik Umar Khan, has died of the disease. 
 
 Government officials hailed Dr Khan, 39, as a "national hero". 
 
 The government disclosed last week that he was being treated for Ebola and had been quarantined. 
 
 His death follows that of prominent Liberian doctor Samuel Brisbane at the weekend. 
 
 Police deployed 
 
 Ebola kills up to 90% of those infected, but patients have a better chance of survival if they receive early treatment. 
 
 It spreads through contact with an infected person's bodily fluids. 
 
 The outbreak - the world's deadliest to date - was first reported in Guinea in February. It then spread to Liberia and Sierra Leone. 
 
 Image copyright other Image caption Liberia tied Independence Day celebrations on 26 July to efforts to create more awareness around Ebola 
 
 Image copyright EPA Image caption Greater emphasis is being placed on hygiene in an effort to contain the virus 
 
 Image copyright EPA Image caption People have also been urged to wear protective gloves 
 
 Asky is the second airline, after Nigeria's largest airline, Arik Air, to ban flights to Liberia and Sierra Leone. 
 
 It had not halted flights to Guinea, but passengers departing from there would be "screened for signs of the virus", Asky said. 
 
 Last week, Nigeria, Africa's most populous country, reported its first case - that of Liberian finance ministry official Patrick Sawyer who flew to the main city, Lagos, in an Asky flight. 
 
 Liberia has deployed police officers at the international airport in the capital, Monrovia, to ensure passengers are screened for symptoms of Ebola. 
 
 Football ban 
 
 "We have a presence of the police at the airport to enforce what we're doing,'' said Binyah Kesselly, chairman of the Liberia Airport Authority. 
 
 "So if you have a flight and you are not complying with the rules, we will not allow you to board.'' 
 
 Ebola since 1976 
 
 Most border crossings in Liberia have been closed to contain the outbreak and affected communities are being quarantined. 
 
 Liberia has also suspended all football activities in an effort to control the spread of Ebola. 
 
 "Football being a contact sport - people are sweating - they do contact each other, and that could result in contracting the disease," the president of its football association, Musa Hassan Bility, told the BBC. 
 
 "It also has to do with the fans because whenever there is a game, a lot of people come together and we want to discourage gathering at this point," he said. 
 
 The association had also told football governing body Fifa to cancel trips to Liberia scheduled for August and September because "we do not want the life of the Fifa president [Sepp Blatter] to be exposed to this disease", Mr Bility said. 
 
 In a statement, the UN World Health Organization (WHO) said that 1,201 Ebola cases had been reported in Guinea, Liberia and Sierra Leone. 
 
 Of the 672 deaths, the highest number was in Guinea with 319, followed by Sierra Leone with 224 and Liberia with 129, it said. 
 
 Media playback is unsupported on your device Media caption The current outbreak is the deadliest since Ebola was discovered in 1976 
 
 The BBC's Jonathan Paye Layleh in Monrovia says that public awareness campaigns around Ebola have been stepped up in the city. 
 
 Many people are worried about the outbreak, and fewer people are going to restaurants and entertainment centres, he says. 
 
 Ebola virus disease (EVD) 
 
 Image copyright Science Photo Library ||||| DAKAR, Senegal (AP) — No one knows for sure just how many people Patrick Sawyer came into contact with the day he boarded a flight in Liberia, had a stopover in Ghana, changed planes in Togo, and then arrived in Nigeria, where authorities say he died days later from Ebola, one of the deadliest diseases known to man. 
 
 A sign at Southside Church of Christ offers support for Dr. Kent Brantly who is being treated for Ebola in Liberia, on Sunday, July 27, 2014, in Fort Worth, Texas. The doctor has been treating Ebola patients... (Associated Press) 
 
 In this photo taken on Sunday, July 27, 2014, a boy, center, selling soft drinks walk past a clinic taking care of Ebola patients in the Kenema District on the outskirts of Kenema, Sierra Leone. Liberia... (Associated Press) 
 
 In this photo taken on Sunday, July 27, 2014, Medical personnel inside a clinic taking care of Ebola patients in the Kenema District on the outskirts of Kenema, Sierra Leone. Liberia President Ellen... (Associated Press) 
 
 Now health workers are scrambling to trace those who may have been exposed to Sawyer across West Africa, including flight attendants and fellow passengers. 
 
 Health experts say it is unlikely he could have infected others with the virus that can cause victims to bleed from the eyes, mouth and ears. Still, unsettling questions remain: How could a man whose sister recently died from Ebola manage to board a plane leaving the country? And worse: Could Ebola become the latest disease to be spread by international air travel? 
 
 Sawyer's death on Friday has led to tighter screening of airline passengers in West Africa, where an unprecedented outbreak that emerged in March has killed more than 670 people in Guinea, Sierra Leone and Liberia. But some health authorities expressed little confidence in such precautions. 
 
 "The best thing would be if people did not travel when they were sick, but the problem is people won't say when they're sick. They will lie in order to travel, so it is doubtful travel recommendations would have a big impact," said Dr. David Heymann, professor of infectious diseases at the London School of Hygiene and Tropical Medicine. 
 
 "The important thing is for countries to be prepared when they get patients infected with Ebola, that they are isolated, family members are told what to do and health workers take the right steps." 
 
 The World Health Organization is awaiting laboratory confirmation after Nigerian health authorities said Sawyer tested positive for Ebola, WHO spokesman Gregory Hartl said. The WHO has not recommended any travel restrictions since the outbreak came to light. 
 
 "We would have to consider any travel recommendations very carefully, but the best way to stop this outbreak is to put the necessary measures in place at the source of infection," Hartl said. Closing borders "might help, but it won't be exhaustive or foolproof." 
 
 The risk of travelers contracting Ebola is considered low because it requires direct contact with bodily fluids or secretions such as urine, blood, sweat or saliva, experts say. Ebola can't be spread like flu through casual contact or breathing in the same air. 
 
 Patients are contagious only once the disease has progressed to the point they show symptoms, according to the WHO. And the most vulnerable are health care workers and relatives who come in much closer contact with the sick. 
 
 Still, witnesses say Sawyer, a 40-year-old Liberian Finance Ministry employee en route to a conference in Nigeria, was vomiting and had diarrhea aboard at least one of his flights with some 50 other passengers aboard. Ebola can be contracted from traces of feces or vomit, experts say. 
 
 Sawyer was immediately quarantined upon arrival in Lagos — a city of 21 million people — and Nigerian authorities say his fellow travelers were advised of Ebola's symptoms and then were allowed to leave. The incubation period can be as long as 21 days, meaning anyone infected may not fall ill for several weeks. 
 
 Health officials rely on "contact tracing" — locating anyone who may have been exposed, and then anyone who may have come into contact with that person. That may prove impossible, given that other passengers journeyed on to dozens of other cities. 
 
 Patrick Sawyer had planned to visit his family in Minnesota next month to attend two of his three daughters' birthdays, his wife, Decontee Sawyer, told KSTP-TV in Minnesota. 
 
 "It's a global problem because Patrick could have easily come home with Ebola, easy," she said. The Associated Press left phone and email messages for her Monday. 
 
 International travel has made the spread of disease via airplanes almost routine. Outbreaks of measles, polio and cholera have been traced back to countries thousands of miles away. Even Ebola previously traveled the globe this way: During an outbreak in Ivory Coast in the 1990s, the virus infected a veterinarian who traveled to Switzerland, where the disease was snuffed out upon arrival and she ultimately survived, experts say. 
 
 Two American aid workers in Liberia have tested positive for the virus and are being treated there. U.S. health officials said Monday that the risk of the deadly germ spreading to the United States is remote. 
 
 The mere prospect of Ebola in Africa's most populous nation has Nigerians on edge. 
 
 In Nigeria's capital, Abuja, Alex Akinwale, a 35-year-old entrepreneur, said he is particularly concerned about taking the bus, which is the only affordable way to travel. 
 
 "It's actually making me very nervous. If I had my own car, I would be safer," he said. "The doctors are on strike, and that means they are not prepared for it. For now I'm trying to be very careful." 
 
 It's an unprecedented public health scenario: Since 1976, when the virus was first discovered, Ebola outbreaks were limited to remote corners of Congo and Uganda, far from urban centers, and stayed within the borders of a single country. This time, cases first emerged in Guinea, and before long hundreds of others were stricken in Liberia and Sierra Leone. 
 
 Those are some of the poorest countries in the world, with few doctors and nurses to treat sick patients let alone determine who is well enough to travel. In Sawyer's case, it appears nothing was done to question him until he fell sick on his second flight with Asky Airlines. An airline spokesman would not comment on what precautions were being taken in the aftermath of Sawyer's journey. 
 
 Liberian Assistant Health Minister Tolbert Nyenswah told The Associated Press last week that there had been no screening at Liberia's Monrovia airport. That changed quickly over the weekend, when President Ellen Johnson Sirleaf said a new policy on inspecting and testing all outgoing and incoming passengers will be strictly observed. She also announced that some borders were being closed and communities with large numbers of Ebola cases would be quarantined. 
 
 International travelers departing from the capitals of Sierra Leone and Guinea are also being checked for signs of fever, airport officials said. Buckets of chlorine are also on hand at Sierra Leone's airport in Freetown for disinfection, authorities said. 
 
 Still, detecting Ebola in departing passengers might be tricky, since its initial symptoms are similar to many other diseases, including malaria and typhoid fever. 
 
 "It will be very difficult now to contain this outbreak because it's spread," Heymann said. "The chance to stop it quickly was months ago before it crossed borders ... but this can still be stopped if there is good hospital infection control, contact tracing and collaboration between countries." 
 
 Nigerian authorities so far have identified 59 people who came into contact with Sawyer and have tested 20, said Lagos State Health Commissioner Jide Idris. Among them were officials from ECOWAS, a West African governing body, airline employees, health workers and the Nigerian ambassador to Liberia, he said. He said there have been no new cases of the disease. 
 
 ___ 
 
 Associated Press Medical Writer Maria Cheng reported from London. Jonathan Paye-Layleh in Monrovia, Liberia; Clarence Roy-Macaulay in Freetown, Sierra Leone; Erick Kaglan in Lome, Togo; and Heather Murdock in Abuja, Nigeria, also contributed to this report. 
 
 ___ 
 
 Follow Krista Larson at https://www.twitter.com/klarsonafrica ||||| (From L to R) Abdulsalami Nasidi, director of the Nigeria Centre for Disease Control (NCDC), Lagos state health commissioner Jide Idris and Lagos Special Advisor on Health Yewande Adesina, speak about the update on the Ebola outbreak during a news conference in Lagos July... 
 
 LAGOS The Nigerian city of Lagos shut and quarantined a hospital on Monday where a Liberian man died of the Ebola virus, the first recorded case of the highly-infectious disease in Africa's most populous country. 
 
 Patrick Sawyer, a consultant for Liberia's Finance Ministry in his 40s, collapsed on arrival at the Lagos airport on July 20. He was put in isolation at the First Consultants Hospital in Obalende, one of the most crowded parts of a city that is home to 21 million people. He died on Friday. 
 
 "The private hospital was demobilized (evacuated) and the primary source of infection eliminated. The decontamination process in all the affected areas has commenced," Lagos state health commissioner Jide Idris told a news conference. He said the hospital would be closed for a week and the staff would be closely monitored. 
 
 Ebola has killed 672 people in Guinea, Liberia and Sierra Leone since it was first diagnosed in February. The fatality rate of the current outbreak is around 60 percent although the disease can kill up to 90 percent of those who catch it. Highly contagious, its symptoms include vomiting, diarrhea and internal and external bleeding. 
 
 In Sierra Leone, which has the highest number of Ebola cases in the current outbreak at 525, President Ernest Bai Koroma visited an Ebola center in the northeastern district of Kenema. 
 
 An administration official said President Barack Obama was receiving updates, and noted that U.S. agencies had stepped up assistance to help contain the virus. 
 
 Susan Rice, Obama's national security adviser, said in a televised interview on Monday the outbreak was of "grave concern." 
 
 "We are very much present and active in trying to help the countries of the region and the international authorities like the World Health Organization address and contain this threat. But it is indeed a very worrying epidemic," Rice told MSNBC. 
 
 HOSPITAL STAFF, OTHERS MONITORED 
 
 Authorities were monitoring 59 people who were in contact with Sawyer, including airport contacts, the Lagos state health ministry said, but it said the airline had yet to provide a passenger list for the flights Sawyer used. 
 
 Derek Gatherer, a virologist at Britain's University of Lancaster, said anyone on the plane near Sawyer could be in "pretty serious danger," but that Nigeria was better placed to tackle the outbreak than its neighbors. 
 
 "Nigerians have deep pockets and they can do as much as any Western country could do if they have the motivation and organization to get it done," he said. 
 
 Nigeria's largest air carrier Arik Air has suspended flights to Liberia and Sierra Leone because of the Ebola risk, Arik spokesman Ola Adebanji said in an email on Monday. 
 
 "RED ALERT" 
 
 David Heymann, head of the Centre on Global Health Security at London's Chatham House, said every person who had been on the plane to Lagos with Sawyer would need to be traced and told to monitor their temperature twice a day for 21 days. 
 
 The World Health Organization said in a statement that Sawyer's flight had stopped in Lomé, Togo, on its way to Lagos. 
 
 "WHO is sending teams to both Nigeria and Togo to do follow- up work in relation to contact tracing, in particular to contacts he may have had on board the flight," spokesman Paul Garwood said. 
 
 Liberia closed most of its border crossings and introduced stringent health measures on Sunday, a day after a 33-year-old American doctor working there for the relief organization Samaritan's Purse tested positive for Ebola. 
 
 Nigeria's airports, seaports and land borders have been on "red alert" since Friday over the disease. 
 
 Exacerbating the difficulty of containing the virus, Nigerian doctors are on strike over conditions and pay. 
 
 The WHO said that in the past week, its regional director for Africa, Luis Sambo, had been on a fact-finding mission to Guinea, Liberia and Sierra Leone, which have 1,201 confirmed, suspected and probable cases among them. 
 
 "He observed that the outbreak is beyond each national health sector alone and urged the governments of the affected countries to mobilize and involve all sectors, including civil society and communities, in the response," the WHO said. 
 
 (Reporting by Tim Cocks, additional reporting by Oludare Mayowa in Lagos, Tom Miles in Geneva, Kate Kelland in London, Roberta Rampton in Washington, and Umaru Fofana in Freetown; writing by Toni Reinhold, editing by G Crosse)
– Dr. Sheik Umar Khan, one of the leading doctors fighting Sierra Leone's Ebola outbreak, died today of the virus in yet another high-profile casualty, reports the BBC. The death of the man hailed by the government as a "national hero" comes as Nigeria, the continent's most populous country, recorded its first case of the infectious disease, reports Reuters. The death was that of a Liberian consultant who collapsed in the Lagos airport on July 20, and health authorities have quarantined the hospital that cared for him. Meanwhile, American doctor Kent Brantly has a "grave" prognosis in Liberia as his family in Texas asks for prayers, reports the Fort Worth Star-Telegram. The 33-year-old tested positive last week. Liberia has closed its border crossings; Nigeria’s airports, seaports, and borders have been on "red alert"; and West African airports are screening passengers for signs of illness. Since February, 1,200 people have been infected with Ebola, and 672 people in Guinea, Liberia, and Sierra Leone have died; the fatality rate in this outbreak is 60%. Here’s what you need to know about Ebola: It's possible that Ebola can jump from animals to humans through "bush meat" such as apes, monkeys, antelope, and porcupines, reports NBC News. Once an outbreak starts, it moves from person to person. The fatality rate is 50% to 90%. Early treatment is vital. The virus spreads through bodily fluids such as vomit and diarrhea; it’s infectious when the victim shows symptoms and remains so after the patient's death. Many have contracted Ebola by preparing a corpse for burial. Up to 60% of patients will bleed from the eyes and skin. There is no cure, and antivirals aren’t effective. The only way to get a diagnosis is with a blood test, adds the Wall Street Journal.