The world has never seen an outbreak of Ebola as bad as the one that’s now ravaging West Africa. The often-fatal disease first struck humans nearly 40 years ago, in 1976. However, the current epidemic has claimed far more lives than in other years. As of September 12, more than 4,780 people had been infected, of which 2,400 had died. New studies are pointing to how the latest outbreak started — and which new medicines and vaccines might finally slow its spread.

For instance, Stephen Gire of Harvard University in Cambridge, Mass., and his co-workers have just homed in on the origin of the virus infecting people in the West African country of Sierra Leone. More than 50 researchers, from four countries, studied virus samples from 78 people. These patients had all come down with the disease in the early weeks of the outbreak. Collecting the virus from them proved dangerous. Indeed, five of the researchers died from Ebola before their new data were published.

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Gire’s group isolated 99 Ebola viruses from the infected people. A genome is the collection of all the genetic material in an organism. By studying the Ebola genomes, the researchers learned that the virus circulating among people in West Africa has 341 genetic changes never before seen in this germ.

Genes in the virus are changing rapidly as the disease spreads, these data show. Those changes may occur when the virus lives in animals between outbreaks in people. Or the virus may change quickly once it begins moving through a human population, as now. The quick-changing nature of Ebola’s genes may be important. If drugs or vaccines are developed to treat earlier forms of the virus, there’s a chance they might not work against later versions.

The new analysis by Gire’s group suggests that the spread of the West African epidemic is not from continuing new infections from animals. Instead, the data support the idea that the current outbreak began with one boy in Guinea. He became infected by some animal. Before he died, he spread Ebola to others. A healer from neighboring Sierra Leone encountered one of the newly infected people when he visited Guinea. He too became infected. Later he went home and died. Mourners at his funeral picked up the disease, the genetic data show. That launched Ebola’s spread in that country. Gire’s group reported these findings in the Aug. 28 Science.

So far this year, people in five West African nations and the Congo have developed Ebola.

Anthony Fauci is the director of the National Institute of Allergy and Infectious Diseases in Bethesda, Md. Even as recently as five years ago, scientists would have found it impossible to quickly conduct genetic studies such as this one on Ebola, he says. But thanks to new technologies, researchers can study changes to a germ’s genes during an outbreak.

“Now, as we’re living through it, we’re able to trace the spread of the virus,” Fauci told Science News.

Help may be coming

There is no known cure for Ebola. There also are no approved vaccines to prevent the disease. The best doctors can do now is treat the symptoms. For instance, they may pump fluids into a patient’s veins to curb dehydration.

West Africa is experiencing the worst outbreak of Ebola in history. New studies show it’s changing fast. But several treatments and two vaccines soon may be ready for testing in people. Credit: Source: S.K. Gire et al/Science 2014

However, doctors have been testing drugs and vaccines. In the Sept. 7 Nature Medicine, researchers reported that a vaccine tested on monkeys shows strong promise. Vaccines will not cure disease. They are designed to prevent infection in the first place.

Scientists developed one new vaccine by adding Ebola genes to a virus that gives chimpanzees the common cold. The researchers injected four animals with one form of the vaccine. Eight weeks later, they gave the monkeys a booster shot with a slightly different form of the vaccine. Ten months after that, they exposed each monkey to Ebola. None developed the disease.

Researchers don’t yet know if this vaccine also will protect humans. But they have moved to the next step: testing it for safety in people. They are recruiting healthy human volunteers. Two of the new vaccines might be ready for use in Africa by November, scientists say.

Scientists also have just reported success with one of several new experimental treatments for Ebola. Such drugs might offer a cure. In one study, they gave a drug called Zmapp to 18 Rhesus macaque monkeys. Every one of them survived exposure to the disease, the scientists reported in the Aug. 29 Nature. Seven people sickened during the ongoing West African epidemic also have received the drug — although not as part of this or any study. At least two of them have died. It’s possible, though, that they may have been treated too late or with too little medicine to be helpful. At this point, there’s no way to tell.

Other new drugs that have so far only been tested in animals will soon be made available to treat sick people in Africa. Currently, no one knows how well they might work. But conditions in West Africa are so bad that doctors are desperate to try about anything that shows promise.

On August 28, the World Health Organization, or WHO, released a report on the status of the West African outbreak. WHO health researchers think the epidemic there is still building. It could last another six to nine months, they predict. By the time it ends, up to 20,000 people may have been sickened, the new report says — perhaps even more.

Power Words

Ebola A family of viruses that cause a deadly disease in people. Most cases occur in Africa and Asia. Its symptoms include headaches, fever, muscle pain and extensive bleeding. The infection spreads from person to person (or animal to some person) through contact with infected body fluids.

epidemic A widespread outbreak of an infectious disease that sickens many people in a community at the same time.

gene (adj. genetic)A segment of DNA that codes, or holds instructions, for producing a protein. Offspring inherit genes from their parents. Genes influence how an organism looks and behaves.

genetic Having to do with chromosomes, DNA and the genes contained within DNA. The field of science dealing with these biological instructions is known as genetics.

genome The complete set of genes or genetic material in a cell or an organism.

germ Any one-celled microorganism, such as a bacterium, fungal species or virus particle. Some germs cause disease. Others can promote the health of higher-order organisms, including birds and mammals. The health effects of most germs, however, remain unknown.

outbreak The sudden emergence of disease in a population of people or animals.

population A group of individuals from the same species that lives in the same area.

reservoir A large store of something. People who study infections refer to the environment in which germs can survive safely (such as the bodies of birds or pigs) as living reservoirs.

scanning electron microscope (SEM) A scientific instrument in which the surface of a specimen is scanned by a beam of electrons that are reflected to form an image.

vaccine A biological mixture that resembles a disease-causing agent. It is given to help the body create immunity to a particular disease.

virus Tiny infectious particles consisting of RNA or DNA surrounded by protein. Viruses can reproduce only by injecting their genetic material into the cells of living creatures. Although scientists frequently refer to viruses as live or dead, in fact no virus is truly alive. It doesn’t eat like animals do, or make its own food the way plants do. It must hijack the cellular machinery of a living cell in order to survive.

World Health Organization An agency of the United Nations, established in 1948, to promote health and to control communicable diseases. It is based in Geneva, Switzerland. The United Nations relies on the WHO for providing international leadership on global health matters. This organization also helps shape the research agenda for health issues and sets standards for pollutants and other things that could pose a risk to health. WHO also regularly reviews data to set policies for maintaining health and a healthy environment.