More than 530 people have died over the last four months from an Ebola virus that's been spreading through the West African nations of Guinea, Sierra Leone and Liberia.
It's the single deadliest outbreak of the disease on record. And because Ebola has no known cure or vaccine and has a near 90-percent death rate, health experts say the rising alarm over the virus is real.
"It's frightening and in some respects more so than HIV, because it has a high mortality rate and kills within days of infection," said John Palisano, a professor of biology at Sewanee: The University of the South.
Palisano said that the outbreak is particularly dangerous because it's occurring along a major hub of global travel in western Africa.
As for the chances of the current Ebola outbreak reaching the U.S., however, it's possible in theory but not likely to be widespread, said Dr. Aileen Marty, a professor of infectious diseases at Florida International University.
"We have access to much better disease control, and we have an excellent and alert journalism population that could warn our citizens," she said.
Ebola was introduced in the U.S. when it was found in quarantined monkeys imported from the Philippines in 1989, 1990 and 1996. But no human infections were discovered.
Still, concerns of its spread can't be ignored, said Dr. Cecilia Rokusek, assistant dean for education, planning and research at Nova Southeastern University.
"Americans generally do not have an immediate danger but they must be prepared through good public health practice. We can no longer become complacent to any public health danger anywhere," she said.
Virus starts with animals
Ebola is a severe and nearly always fatal disease to humans, according to the World Health Organization (WHO). There are several strains with an incubation period of up to 21 days after infection.
The virus is transmitted to people and animals through contact with infected fruit bats. Monkeys, apes, or pigs can become hosts of the virus through contact with fruit bat saliva or feces.
People can also be infected through contact with infected animals, either by slaughtering the animals or through consumption of blood, milk, or raw or under-cooked meat.
The virus can be passed from person to person through direct contact with body fluids of infected persons, or from contact with contaminated needles or even touching something an infected person has touched.
Symptoms include fever, severe weakness, muscle pain, headache and sore throat. This is followed by vomiting, diarrhea, rash, impaired kidney and liver function and, in some cases, both internal and external bleeding.
Without a cure, treatment usually consists of infusing massive amounts of fluids to replace those lost.
Funeral practices help virus spread
Africa has had deadly outbreaks of Ebola before. Going back to 1976, at least 2,000 deaths have resulted from the disease.
This recent outbreak is believed to have started in Liberia. The government there has called the crisis a national public emergency and has urged citizens to follow health guidelines.
It's also threatened to arrest those who hide Ebola victims. Some residents in Liberia are said to be removing patients from hospitals for special prayers or to treat them with local medicine.
"One of the main transmitters are the funeral practices," said Dr. Steven Vryhof, who just returned from Liberia after working there for two weeks with the medical aid group, Mission to Heal.
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Vryhof said many people insist on burying the dead, which means shaving the men and braiding women's hair and so exposing themselves to the Ebola virus.
"The government is doing what it can to educate the people," he said. "But the people are still terrified about the disease. It's a horrible way to die."
What's needed in Liberia and other countries in the region is more private development in areas of sanitation and safe drinking water, said Jones Nhinson Williams, who runs a Liberian public policy group called the New Liberia Foundation.
"The government can't do it all to stop the virus," Williams argued. "They just don't have the economic resources."
'Drastic action needed'
The WHO has said that "drastic action is needed" to contain the virus, which has spread from rural areas to cities.
After a meeting with the health ministers from 11 African countries last week, the WHO came up with several priority actions to reduce the spread of Ebola.
The steps include strengthening surveillance of cases and tracing back contacts of those who get the disease.
But getting ahead of further outbreaks won't be easy, said Dr. Pascal James Imperato, of the SUNY Downstate Medical Center.
"With expansion of human population in places like West Africa, it brings more ordinary people closer to environments where animals live," he said.