miércoles, 6 de agosto de 2014

Ebola diez

Del sitio web Vox (http://www.vox.com/) rescatamos diez puntos relevantes a tener en cuenta en torno a la enfermedad del virus Ebola, actualmente en fase de expansión exponencial.

1. Why is Ebola suddenly in the news?

The deadliest Ebola outbreak in recorded history is happening right now. The outbreak is unprecedented both in infection numbers and in geographic scope. And so far, it's been a long battle that doesn't appear to be slowing down.

The Ebola virus has now hit four countries: Sierra Leone, Guinea, Liberia, and Nigeria. The virus — which starts off with flu-like symptoms and often ends with horrific hemorrhaging — has infected about 1,300 people and killed more than 700 since this winter, according to estimates on July 31 from the World Health Organization.

Ebola is both rare and very deadly. Since the first outbreak in 1976, Ebola viruses have infected thousands of people and killed roughly 60 percent of them. Symptoms can come on very quickly and kill fast:

Each bar here represents a different Ebola outbreak. The data is what the CDC has on record. Not every case or death always gets officially recorded, so there is always some wiggle room in numbers like these. 2014 is estimate of the current outbreak as of July 23, 2014 from the WHO.

Journalist David Quammen put it well in a recent New York Times op-ed: "Ebola is more inimical to humans than perhaps any known virus on Earth, except rabies and HIV-1. And it does its damage much faster than either."

2. How do Ebola outbreaks happen?

Ebola tends to come and go over time. The viruses are constantly circulating in animals, most likely bats. Every once in a while, the disease spills over into humans, often when someone handles or eats undercooked or raw meat from a diseased ape, monkey, or bat. An outbreak can then happen for several months. And then it becomes quiet again.

Ebola can completely disappear from humans for years at a time. For example, there were zero recorded cases of Ebola in 2005 or 2006. The current outbreak has been going on since late 2013 or early 2014 and has been getting extra attention in the news recently as several doctors have caught the disease, including a Liberian doctor and Sierra Leone's top Ebola doctor (who both died).

3. Where is the current Ebola outbreak?

The current outbreak started in Guinea sometime in late 2013 or early 2014. It has since spread to Sierra Leone and Liberia, including some major capital cities. And one infected patient traveled on a plane to Nigeria, where he then died.

4. Why is the current Ebola outbreak so deadly?

For starters, this outbreak concerns the most deadly of the five Ebola viruses, Zaire ebolavirus, which has killed 79 percent of the people it has infected in previous outbreaks. (The virus is called that after the formerly named Zaire, which, along with Sudan, experienced the first Ebola outbreak back in 1976.)

These death rates were calculated by adding up the records of cases and deaths from all known outbreaks. Individual outbreaks can vary, and Zaire ebolavirus is often cited as having death rates up to 90 percent. Data in this chart doesn't include the most recent 2013-2014 outbreak.

There are also social and political factors contributing to the current disaster. Because this is the first major Ebola outbreak in West Africa, many of the region's health workers didn't have experience or training in how to protect themselves or care for patients with this disease.

What's more, an NPR story suggests that people in these countries tend to travel more than those in Central Africa (where outbreaks usually occur). That may have helped the virus disperse geographically, and it made it difficult to track down people who might be infected.

Meanwhile, as an editorial in the medical journal Lancet noted, social stigmas and a lack of awareness may lead people to not seek medical care (or even avoid it). Another often-cited problem is that some people have had direct contact with victims' dead bodies during funerals and preparations for burial, which can spread the disease.

Some people are afraid that medical workers are causing Ebola, and workers "have been threatened with knives, stones and machetes, their vehicles sometimes surrounded by hostile mobs," according to the New York Times.

The humanitarian group Doctors Without Borders has noted 12 villages in Guinea that might have Ebola but aren't safe for workers. In Sierra Leone, a protest against a clinic led to the police using tear gas. And a World Health Organization assessment in Liberia noted problems with tracing patients' contacts with other people, "persisting denial and resistance in the community," and issues with "inadequate" measures used to prevent and control infections, weak data management, and "weak leadership and coordination," according to a statement released on July 19.

In many ways, how well a country can deal with an Ebola outbreak comes down to basic health-care practices and public education. With enough resources poured into the effort, people should be able to contain this outbreak. So far, however, these countries are really struggling.

5. Does Ebola really make people bleed from their eyes?

Yes. Bleeding from orifices is one of the more unusual and memorable symptoms of viral hemorrhagic fevers like Ebola. In later stages of the disease, some people bleed from the eyes, nose, ears, mouth, and rectum. They may also bleed from puncture sites if they've had an IV.

External bleeding can be one of the main symptoms that can help people realize they're dealing with a case of Ebola, since other signs — first fevers and headache, then vomiting and diarrhea — can be caused by any number of illnesses. Internal bleeding can happen, as well.

But it doesn't always happen. For example, this study of a 1995 outbreak in found external bleeding in 41 percent of cases. And bleeding didn't correlate with who survived and who didn't.

What actually kills people is shock from multiple organ failure, including problems with the liver, kidneys, and central nervous system. Symptoms come on abruptly after an incubation period of 2 to 21 days. And people generally die between day 6 and 16 of the illness.


6. Why is Ebola so deadly?

One of the main things that seems to make Ebola viruses especially deadly is that they seem to be able to evade much of the human immune system. Among other problems, white blood cells from the immune system are often seen to die off in patients. And if the body can't fight fully back, the virus can just keep taking over.

Scientists are still figuring out exactly how this happens, and they have several promising leads. One is that the virus is making proteins that act as decoys, interfering with the body's ability to fight back.

7. How hard is it to catch Ebola?

Ebola doesn't tend to hang out in the air like some other viruses, such as measles, SARS, or some kinds of the flu.

 In order to contract Ebola, someone must touch the blood or bodily fluids (including sweat, urine, and semen) of a person or animal who's infected (alive or dead). People can also catch it through indirect contact with victims' fluids, such as via bedding or medical equipment.

People generally aren't infectious until they get sick. Ebola's limited transmission ability is one of the main reasons why outbreaks can often be stopped within weeks or months. What it takes is public education and good health-care hygiene like isolating patients, sterilization procedures, and the use of gloves, masks, and other protective gear.

8. How do you treat Ebola?

Patients are treated for symptoms, including IV fluids for dehydration. It's important to remember that some people do survive an Ebola infection.

Hopefully, in the future there will be more options. For example, researchers are workingto find drugs, including a recent $50 million push at the National Institutes of Health. And scientists are working on vaccines, including looking into ones that might be able to help wild chimpanzees, which are also susceptible to the disease.

9. Where the outbreak is occurring now, and where Ebola will go next

There have been confirmed cases of Ebola in four countries: Guinea, Liberia, and Sierra Leone (which share borders) and Nigeria. The burden of the disease is in Sierra Leone, Guinea and Liberia right now. There have only been a handful of cases Nigeria, the most recent being a Lagos nurse who died after treating Nigeria's first Ebola victim, the Liberian-American Patrick Sawyer.

There are suspected Ebola cases in Europe, Asia, and North America but none are confirmed. Public health officials are relatively unconcerned about Ebola becoming a big problem in the developed world. That's because outbreaks persist in countries with poor sanitation and a shortage of resources to contain them, not in resource-rich places like the US.

For this reason, spread within Africa is really what public health officials are worried about. "Our first concern is that this is going to go into adjacent areas through people traveling in the region," said Daniel Bausch, associate professor at the Tulane University School of Public Health and Tropical Medicine, who is working with the WHO and MSF on the outbreak. "In the short term, the main vector is the traveler: local people traveling from one village to the next, on more regional scale, plane travellers."

This pie chart shows the final destinations of travellers originating in the three countries currently most affected by Ebola. As you can see, travel from Sierra Leone, Guinea and Liberia within the continent is much more prevalent than travel elsewhere.

ll countries in West Africa are already on alert. National authorities in Ghana, Nigeria, Togo and the Côte d'Ivoire are working with the WHO on prevention efforts and monitoring potential cases.

To do this, contact tracing is essential, said Bausch. "With Ebola outbreaks, most of the time there's one or very few introductions of the virus from the wild into humans, and all the transmission after that is human-to-human transmission. So people who are traveling locally as well as on planes and other modes of transport, that's the way this would get around."

These efforts are already underway in Nigeria, where the disease hasn't yet turned into a full-scale outbreak but there are concerns that it might. Some 70 people who came into contact with a recently diagnosed Ebola doctor have been quarantined, said Dr. Ezie Patrick, the executive director for Africa with the World Medical Association who is based in Nigeria.

But resources to deal with more potential cases aren't presenting themselves, he added. "In the current process, we don't have the facilities to isolate the patients," he said. When there's a suspected case of Ebola, it's reported to the Nigerian centers for disease control and they take over the case management. Patients often need to be moved from their homes to city centers. "When patients are moved from a rural to urban areas," Patrikck added, "the risk of spread increases exponentially."

10. Which is the worst-case scenario

Even if the outbreak didn't move across any other country border, intensification within the already affected areas is the most immediate health threat.

"The worst-case scenario is that the disease will continue to bubble on, like a persistent bushfire, never quite doused out," said Derek Gatherer, a Lancaster University bioinformatician who has studied the evolution of this Ebola outbreak. "It may start to approach endemic status in some of the worst affected regions. This would have very debilitating effects on the economies of the affected countries and West Africa in general." "Ebola may start to approach endemic status in some of the worst affected regions."

This dire situation could come about because of a "persistent failure of current efforts," he added. "Previous successful eradications of Ebola outbreaks have been via swamping the areas with medical staff and essentially cutting the transmission chains. Doing that here is going to be very difficult and expensive. We have little option other than to pump in resources and engage with the problem using the tried-and-tested strategy—but on a scale previously unused."

Resources are already extremely constrained in most of the countries affected right now. As Dr. Bausch said, "If you're in a hospital in Sierra Leone or Guinea, it might not be unusual to say, 'I need gloves to examine this patient,' and have someone tell you, 'We don't have gloves in the hospital today,' or 'We're out of clean needles,' — all the sorts of things you need to protect against Ebola."

In these situations, local health-care workers — the ones most impacted by the disease — start to get scared and walk off the job. And the situation worsens. "There were 55 people in the Ebola ward, and myself and one other doctor." When Bausch was in Sierra Leone last month, he said all the nurses went on strike in one of the hospitals where he was working. "There were 55 people in the Ebola ward," he said, "and myself and one other doctor."

He'd walk into the hospital in the morning and find patients on the floor in pools of vomit, blood, and stool. They had fallen out of their beds during the night, and they were delirious. "What should happen is that a nursing staff or sanitation officer would come and decontaminate the area," he said. "But when you don't have that support, obviously it gets more dangerous." So the disease spreads.

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