DAKAR, Senegal (AP) -- No one knows for sure just how many people Patrick Sawyer came into contact with the day he boarded a plane in Liberia, had a layover in Togo and then arrived in Nigeria where authorities say he died days later from Ebola, one of the world's deadliest diseases.
Now health workers are scrambling to trace those who may have been exposed to Sawyer at three international airports in West Africa, from flight attendants to fellow passengers. Health experts say it's unlikely he could have infected others with the virus that can cause victims to bleed from their 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? Could Ebola become the latest disease to be spread by airplanes?
"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, 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 official confirmation from a laboratory in Dakar, Senegal, after Nigerian health authorities said Sawyer tested positive for Ebola, said Gregory Hartl, a Geneva-based spokesman.
The WHO has not recommended any travel restrictions since the unprecedented outbreak first emerged in the West African nation of Guinea back in March. At least 319 people now have died in Guinea, along with 224 victims in Sierra Leone along with 129 deaths in Liberia. Among the sick are two American health workers.
"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," he 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 body fluids or secretions like 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 only contagious 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 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, sparking fear of possible fluid transmission. A person could contract it from traces of feces or vomit, health experts say.
Sawyer was immediately put into quarantine upon arrival in Lagos -- a city of 21 million people -- and Nigerian authorities say his fellow travelers were advised of what Ebola symptoms to watch out for and then were allowed to leave. The incubation period can be as long as 21 days, complicating the effort to trace who may be infected because they may not fall ill for several weeks.
Health officials rely on "contact tracing" -- the process of locating anyone who may have been exposed, and then anyone who may have come into contact with that person. That may prove an impossible task given that other transiting passengers in Lome, Togo, where Sawyer had his stopover, have journeyed on to dozens of other cities.
"We are actively trying to find the whereabouts of all the passengers who took the same flights to and from Lome as that patient," said Napo Koura Gado, an official with the Togolese health ministry.
International travel has made disease spread via airplanes almost routine; past outbreaks of measles, polio and cholera have all been traced back to countries thousands of miles from where the germs first originated. Even Ebola has previously traveled the globe this way: During a previous outbreak in Ivory Coast in the 1990s, the virus infected a veterinarian who traveled to Switzerland, where the disease was snuffed out upon its arrival and she ultimately survived, experts say.
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's 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 staying within the borders of a single country. Cases first emerged in the West African nation of Guinea in March and before long others fell in Liberia and Sierra Leone.
Those countries are among the poorest in the world with few doctors and nurses to treat sick patients let alone to determine who is well enough to travel at an airport. In Sawyer's case, it appears nothing was done to question him or others until he fell sick on his second flight with Asky Airlines. An airline spokesman declined to 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 the Monrovia airport. That changed quickly over the weekend though when President Ellen Johnson Sirleaf announced that all borders were being closed except for major entry posts and the international airport.
A new travel policy by the Liberia Airport Authority covering inspection and testing of all outgoing and incoming passengers will be strictly observed, she said. And communities with large numbers of Ebola cases are to be quarantined too.
International flights also are departing from the capitals of Sierra Leone and Guinea, though airport officials there say they're already checking for signs of fever in departing passengers. Buckets of chlorine are also on hand at the airport in Freetown for disinfection purposes, said Sidie Yayah Tunis, director of communications for the Ministry of Health and Sanitation.
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."
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 Murdoch in Abuja, Nigeria also contributed to this report.
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