(MONROVIA, Liberia) — A high profile doctor in Liberia, Dr. Samuel Brisbane has died of the deadly Ebola disease while an American physician was being treated for virus. This brings to the forefront the risks facing health workers trying to fight a deadly outbreak that has killed more than 680 people in West Africa — the largest ever recorded.

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Another American, a missionary working in the Liberian capital, has also contracted the virus and is currently being treated, said the sponsor of her work, a pastor of a North Carolina church.

While treating Ebola patients at the country’s largest hospital, the John F. Kennedy Memorial Medical Center in Monrovia, Dr. Samuel Brisbane contracted the virus and died on Saturday reported Tolbert Nyenswah, an assistant health minister. A Ugandan doctor had already died earlier this month.

33-year-old Dr. Kent Brantly, an American physician, was helping to treat patients when he also fell ill with the deadly virus. Currently in a stable condition, he is receiving intensive medical care in a Monrovia hospital.

Early treatment improves a patient’s chances of survival, and Dr Brantly recognized his own symptoms and began receiving care immediately so while he is stable it is not clear if he will fully recover yet.

The American missionary, Nancy Writebol, is dangerously ill and in isolation in a Monrovia hospital, her husband, David Writebol, told a church elder via Skype, according to the Rev. John Munro, pastor of Calvary Church in Charlotte, N.C.

Despite the deadly Ebola threat, Munro said the couple, who had been in Liberia for about a year, insisted on staying. “These are real heroes — people who do things quietly behind the scenes, people with a very strong vocation and very strong faith,”

Ebola is one of the deadliest viruses in the world and is also highly contagious with no known cure. At least 1,200 people have been infected in Liberia, Sierra Leone and Guinea, according to the World Health Organization, and 675 have died. Besides the Liberian fatalities, 321 people have died in Guinea and 226 in Sierra Leone.

Ebola virus disease (EVD) or Ebola hemorrhagic fever (EHF) is the human disease caused by ebola viruses. Symptoms start two days to three weeks after contracting the virus with a fever, throat and muscle pains, and headaches. There is then nausea, vomiting and diarrhea along with decreased functioning of the liver and kidneys. At this point some people begin to have problems with bleeding.

Ebola is first acquired when a person comes into contact with the blood or bodily fluids of an infected animal such as a monkey or fruit bat. Fruit bats are believed to carry and spread the disease without being affected by it. Once infection occurs, the disease rapidly spreads from one person to another. Men who survive may be able to transmit the disease sexually for nearly two months

Nigerian authorities have reported that a Liberian man died of Ebola after flying from Monrovia to Lagos via Lome, Togo. The incident showed how difficult it is containing the disease and preventing Ebola victims from travelling considering the symptoms resemble of a fever and sore throat resemble many of illnesses.

Health workers working with patients are among those at greatest risk of contracting the disease, which spreads through contact with bodily fluids.

Photos of Dr Brantly 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.

Ironically, earlier this year, Dr Brantly 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.

The WHO says the disease is not contagious until a person begins to show symptoms. Brantly’s wife and children who had been living with him in Liberia had luckily flown home only the week before he showed any signs of the illness.

In addition to Dr Kent Brantly, a doctor in Liberia’s central Bong County has also fallen ill.

The situation “is getting more and more scary,” said Nyenswah, the country’s assistant health minister.

The fact that a sick Liberian could board a flight to Nigeria raised new fears that other passengers could take the disease beyond Africa.

Nigeria’s international airports, ports and land borders are now on high alert and screening passengers arriving from foreign countries. Togo’s government also said it was on high alert to stop the spread of the disease.

Security analysts were skeptical about the effectiveness of these measures.

“In Nigeria’s case, the security set-up is currently poor, so I doubt it will help or have the minimum effectiveness they are hoping for,” said Yan St. Pierre, CEO of the Berlin-based security consulting firm MOSECON.

An outbreak in Lagos, a megacity where many lived in cramped conditions, could be a potential major public health disaster.

The West Africa outbreak is believed to have begun as far back as January 2014 in southeast Guinea, however the first cases weren’t confirmed until March.

Since then, officials have tried to contain the disease by isolating victims and educating populations on how to avoid transmission, however, weak border control and widespread distrust of health workers has made the Ebola outbreak difficult to bring under control.

News of the Liberian Doctor’s (Brisbane) death first began circulating on Saturday, which was also a national holiday marking Liberia’s independence in 1847.

President Ellen Johnson Sirleaf used her Independence Day address to discuss a new taskforce to combat Ebola. Information Minister Lewis Brown said the taskforce would go “from community to community, from village to village, from town to town” to try to increase awareness.

Saudata Koroma, a hair dresser in Sierra Leone fell ill in the Capital, Freetown is said to be the first case in the area. She was forcibly removed from a government hospital by her family, sparking a frantic search that ended on Friday. The chief medical officer, Kargbo, said that Koroma had died while being transported to a treatment centre in the east of the country.

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