1. According to the article Where does Ebola hide between epidemics? How is it expected that humans may have first contracted the Ebola virus?
According to the National Geographic article, Ebola may hide in fruit bats or in birds between epidemics. The CDC states that scientists are not sure where Ebola comes from, but it is believed to be zoonotic (i.e., transmitted from animals). Because Ebola has been found to be native in two geographical regions, it may have different vectors in the regions.
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Ebola is deadly for non-human primates such as monkeys and great apes. It is believed that humans first contracted Ebola through eating the meat of non-human primates — a common practice in Africa — or through other direct contact with the primates’ bodily fluids such as blood. In this case, the primates would contract the virus from its reservoir (e.g. fruit bats), then humans contract it from primates.
People within the geographic area of Ebola also eat bats, which would directly pass the virus from the reservoir to humans. The authors point out that the bats could also be an intermediate step, and the reservoir some other animal which infects.
2. What are the suspected reservoirs for the Ebola virus?
At present, fruit bats, and possibly birds, are considered the most likely reservoirs of Ebola.
3. Knowing the reservoirs for a virus can help to determine its natural geographic range. Why do you think knowing the likely geographic range of a potentially deadly virus would be important?
If the most likely geographic range for a potentially deadly virus were known, then education about transmission and symptoms, vaccines (if available), and treatments (if available) could be concentrated in the areas they are most needed. For example, if a vaccine for Ebola is developed, it would be very important for people in central Africa to receive it, while there would be little or no need for North Americans to receive it, since North America is not in the virus’s geographic range.
4. How are non human primates (gorillas, monkeys) affected by the Ebola virus?
Non-human primates can be infected with and die from Ebola virus. It is about as lethal to them as it is to us. They generally have the same type of hemorrhagic symptoms that we do. The one exception is the Ebola Reston strain, which sickens non-human primates, but not humans.
5. Why would knowing other species of animals that can contract and spread Ebola be important to controlling the spread of Ebola to humans?
One way it would help to know about other species is so that people can avoid those species as much as possible, especially when there is an outbreak. It is analogous to tularemia, a disease of rabbits which humans can get. If a person needs rabbits for food, they should know how to spot a rabbit with tularemia. Since many people in Africa need non-human primates for food, but they should know how to avoid those that have Ebola.
Also, if non-human primates tend to get an outbreak first and then it moves into the human population, people should be watching for those animal outbreaks so that they can guard against it spreading to humans.
6. According to the article Ebola in Uganda: Why can’t we cure it? Where does it hide? What are two possible reasons that no vaccine has been developed?
One reason that we cannot cure Ebola is that even though we have known about it for 40 years, it is still mysterious. We know very little about it. Even if we did have a possible treatment or vaccine, Ebola can be difficult to diagnose because the early symptoms are usually non-specific — i.e., they could result from many other diseases that are more common. Also, there are 5 strains of Ebola, 4 of which can cause illness in humans.
Although we don’t yet know where Ebola hides, scientists have some evidence that it is linked to bats. For instance, bats were present in several outbreaks, and experiments have shown bats can survive the virus. Another possibility is that Ebola might have started as an avian virus, like bird flu. It could have moved into bats then into humans, or directly into humans.
According to Sanders, who was quoted in the article, one reason there is no vaccine yet is that no Americans have died of Ebola. If that ever occurs, it is likely that money will be immediately allocated by the government and donated by private foundations to find a vaccine as soon as possible. A second reason that we don’t have a vaccine is the fact that, as mentioned above, Ebola has 4 strains that produce illness in humans, and the surface proteins are different for each of these. It is similar to the multiple strains of viruses like influenza — it took a long time for the flu vaccine to be developed, and even now, sometimes the wrong strains are used.
7. Given the information presented in these articles, does Ebola generally present as an endemic disease, an epidemic, or a pandemic?
Ebola is an epidemic disease in people because it causes outbreaks, but these outbreaks do not spread to large areas of the world, like a pandemic. If it were endemic, a few people would be getting Ebola all the time, and numbers infected would dramatically increase when an epidemic occurred. It is possible that Ebola is endemic in certain animal species, but that is not certain yet.
