One thing that is important to know is that there actually are not any confirmed cases in Sierra Leone [1] or Mali. There were many suspected cases in both countries, but all of them have tested false so far. So for now, at least, it is only active in Guinea and Liberia.
[1]: One clarification is that two people from Sierra Leone died from EVD while they were in Guinea, and their bodies were repatriated to Sierra Leone and buried there. Sierra Leone has since banned repatriation of bodies to mitigate the risk of it spreading through this vector.
The problem with all the epidemiological response protocols to Ebola is that so many are based on laboratory tests and not clinical symptoms (which are admittedly complex since they can mimic other more common African hemorrhagic diseases like hantavirus).
Normally, that's a highly accurate way to diagnose confirmed cases, but in this instance, these same lab tests were highly misleading, since the genome of the Ebola virus responsible for this outbreak had shifted so much that it can not be detected by some of the lab assays used by regional labs. This discrepancy may have even prolonged the outbreak.
You're correct. I was thinking of Lassa when I wrote Hantavirus. Of course, Hantavirus was responsible for the "Four Corners" virus in N. America, and more commonly in S. America, if I recall correctly.
It's been over a decade since I worked in infectious disease epi, and even then not in tropical diseases, so I'm lucky to remember anything at all.
But my point stands: Africa is full of hemorrhagic fevers, which makes symptomatic diagnosis of Ebola difficult.
Here's a Medicines Sans Frontieres Ebola expert answering that very question[1]:
In recent years, MSF has been involved in battling every Ebola epidemic. Once the first case is confirmed by a blood test, every person who cares for an infected patient must wear a hazmat suit, gloves, a mask and protective goggles and exercise extreme caution when administering treatment. Decontamination chambers are generally installed between the isolated patients and the external environment. To confine the epidemic, it is critical to trace the entire transmission chain. All individuals who have had contact with patients who may be contaminated are monitored and isolated at the first sign of infection. The affected communities must also be informed about the illness and the precautions to be taken to limit risks of contamination. Basic hygiene – such as washing one’s hands – can significantly reduce the risk of transmission.
As deadly as Ebola is for the individual patient, it's somewhat easily containable compared to other infections: It spreads via blood or other body fluids, it's not airborne or transmitted via touch. From what I've read somewhat prolonged exposure is required - so pretty basic hospital equipment is sufficient as long as you can keep the patients isolated. Previous outbreaks were contained by isolating the patients and giving them the best care possible until either all perished or overcame the disease.
It's a gruesome sickness but it doesn't have the potential to hop like SARS etc. do.
Ebola Reston has shown signs of being transmissible via air. Although it has only been confirmed to infect crab-eating macaques, the potential to jump to a human host is unsettlingly high. Seeing as from a "virus's perspective" a human and a macaque aren't very different. Our cytoplasmic membranes aren't that morphologically divergent, due to our common lineage. Currently it's unknown if it can affect humans, though there is a fair body of evidence suggesting that it can't. However, it could easily mutate to a human hosts; it's basically just a roll of the evolutionary dice.
Ebola Reston actually infects homo sapiens, but it doesn't produce the deadly hemorrhagic fever symptoms. If Ebola Reston acquired the lethality of Ebola Zaire, it would be a highly dangerous disease.
The prospect is worrisome, since in addition to crab-eating macaques (the animal in which the virus was first discovered), the virus had made the jump to pigs as well. Porcine to human transmission is also a very probable species jump. Since there is more human-pig contact that human-monkey contact, there's a dangerous prospect that a virulent air-spreading form of Ebola could jump the species barrier.
If that occurred we'd be faced with a plague as deadly as Ebola Zaire with the airborne transmission mechanism of Ebola Reston.
But why (how) would a virus evolve deadly symptoms if it doesn't already cause deadly symptoms. I always thought that the rate at which Ebola Zaire kills its hosts is actually a hindrance to its further evolution.
In general do virii tend to evolve deadlier or less deadly symptoms?
It would entirely depend on the ecological niche it's exploiting. Ebola's preferred host (currently unknown, though bats are suspected) isn't human. Though its symptoms on humans are catastrophic, it may be asymptomatic to its primary host. It's effects on humans being only coincidental.
Viruses and bacteria don't need to evolve "linearly", as you imagine. If two related viruses infect the same host, they can swap genes and the "airborne capability" gene can jump from E. Reston to E. Zair. The Reston strain doesn't have to "evolve deadlier symptoms".
It's a random process, and the rate of successful recombination is low, but it's the kind of dice you don't wanna let rolling... This is why more developed countries should start to give a fuck, because once we have a successful recombination it becomes everyone's problem!
(Along other lines, you seem to have the same "pretty wrong" idea of what evolution is and how it works that most people have... evolution is not a "directed" process, and it doesn't always work for the benefit of the "organism" or "species", it's a random search, and informationaly speaking it happens at at the genes level, which doesn't seem to mean much at our multi-cell organism level, but for bacteria and viruses it totally changes the game, as the "things that evolve" are actually the genes that not so infrequently jump "horizontally" from one strain to another... once you go down to the "micro" level, the way real world evolution works is pretty different from the "high school biology textbook definition" that most people have of it... and unfortunately and can produce very nasty results.)
EDIT: to make the prev paragraph clearer: if you have a bunch of species/strains that can share genes, then traits that are detrimental to any of the actual species/trains can actually be favored by evolution, if they increase the survival chances not of any species/strain but, but of a "cluster of genes" that manifests a particular feature, and it can be pretty mathematically complex and unintuitive to think of what makes a "cluster of genes" more "fit" (short term "gene cluster" fitness can be compatible with one of the strains "committing ecological suicide" by evolving capabilities that kill its host and limit it's spread in the process) ...the point is that at this level things work very differently than we imagine and we can't just hope that "evolution will work for the best and save our asses"!
EDIT2: this is not just theory, "gene jumping" happens all the time with flu strains and other viruses (for flu it's its main mechanism of evolution - or "the mechanism of evolution of the flu genes cluster"), but it's not dangerous because the viruses are all well adjusted to the human population and vice-versa ...Ebola, on the other hand, is a virus originating from animals, that hasn't had contact with that many human hosts in its evolutionary history, and also a large percent of the current human population hasn't had any recent ancestors that came in contact with this virus, so this is no "good ol' friend" like the flu, it's quite "alien" to modern humans and it can do lots of damage before achieving some sort of "ecological equilibrium" or before being exterminated by a vaccine and/or effective treatment.
If it were "easily containable compared to other infections", the doctors and nurses who treat the patients wouldn't have to wear full biohazard gear or use isolation wards. They'd simply pop on some gloves and a mask.
This strain of Ebola isn't airborne, but it's plenty virulent -- it spreads through contact with nearly every bodily fluid. Get some on your hands and touch your face (which we all do, hundreds of times a day), and you're in trouble.
Wearing bio-hazard gear is more a function of the mortality rate than anything else. Sure, it's easier to transmit than HIV (where the extremely long asymptomatic phase facilitates transmission), but it's not as easy as the flu. If the flu had an 80% mortality rate, you'd get bio-hazard suits for that too.
There are all manner of infections for which doctors and nurses treat patients with extensive protective gear, or in isolation wards.
Beyond that, as others have mentioned, the really tricky bit is that once we don't have a good treatment for it, so post-exposure prophylaxis isn't really in the cards.
I have, for example, never seen an estimate for the infectiousness of Ebola that puts it anywhere near measles.
The consequences are significantly higher even if the chance of infection is low. Of course, if given the option, medical staff will use much more significant measures.
Layperson here, but based on reading I'm a little more pessimistic. The incubation period can be up to 21 days, and the subject can be infectious during that time [1]. Thus there is a plausible worst-case scenario where an undiagnosed carrier flies to a population centre and comes in contact with a lot of people.
Hopefully this could be prevented by contact tracing and other containment as described above, but if one carrier got out and infected people elsewhere, containment efforts might be unable to keep up.
There's still a prolonged exposure issue. You might get unlucky, but as I understand it you need to take on a certain amount of virus initially for it successfully develop into an infection.
While you might come into contact with a lot of people, it seems like even basic hygeine would be enough during incubation to protect most people.
Part of the problem may be certain animal contacts, such as eating "bush meat" (mentioned in the article, also discussed in the Laurie Garrett book). Maybe a campaign against those practices could be worthwhile
People keep repeating this, but it isn't true. Ebola has an incubation period which can be longer than two weeks, and the disease can be transmitted during the incubation period. This is more than enough time to transmit the disease to more than one other person in a dense population.
The biggest reason we haven't seen larger-scale outbreaks of EVD/EHF is that previous outbreaks have been in geographically remote areas, and that doctors are stomping on it with full force whenever an outbreak occurs. The outbreak going on right now disproves the theory that Ebola just burns itself out quickly.
Indeed. "Stochastic extinction and skilled epidemiologists and clinicians" are vastly more likely explanations than "It's just so good at killing people".
let me guess, you got this from playing Plague Inc. (https://play.google.com/store/apps/details?id=com.miniclip.p...) on your phone, right? ...the game is so unrealistic that it almost annoyed me to the point of motivating me to write a competing more realistic game ...but then I realized that "more realistic" would be too detrimental to the gameplay for it to be enjoyable :)
Diseases, even diseases with pretty absurd transmission potential, can die out in small populations due to random chance. For the most part, previous outbreaks have been in the bush - it's entirely possible the answer is "Because we were lucky"
While the Ebola response mapping jobs are in pretty good shape there are other open tasks where there is plenty of unmapped territory.
With an OSM account you can see the full list at http://tasks.hotosm.org .
E.g. http://tasks.hotosm.org/job/468 is completely undone (albeit 3 squares are being worked on as I write this) and http://tasks.hotosm.org/job/467 has just 3 squares done (with 2 being worked on). Both of these two tasks are linked to US State Department's Humanitarian Information Unit's MapGive program, which BTW has nice video intros/tutorials to getting started with OSM (http://mapgive.state.gov).
It looks like all three regions have been fully traced and validated? This is the first time I've seen this, but it looks like there's nothing to do there, to me.
1. Cases in 2 countries with suspected cases in 2 more [1]
2. Cases in a capital city of 2M+ people
http://www.npr.org/blogs/health/2014/04/08/300509073/the-ebo...
[1] thanks nbouscal