RR Phantom
Location : Wasted Space
Job/hobbies : Cayman Islands Actuary
 |  Subject: Why I'm Concerned About Ebola  Wed Oct 15, 2014 9:39 pm | |
| In June and early July it became clear that the 2014 Ebola outbreak would become bigger than all other historical Ebola outbreaks combined.
The dramatic publicity of the cases in the US illustrates what I’ve known to be the case since June, when I started following the epidemic in great detail: working with Ebola patients is very dangerous. In July, it was clear that approximately 10% of the death toll consisted of healthcare workers. This was easily excused at the time because many of these “healthcare workers” are social workers: they are not nurses or doctors, and many encounter patients without gloves and can go on to reinfect new people.
Doctors Without Borders hasn't lost a single healthcare worker to Ebola in approximately 40 years before this outbreak. But they're highly trained and cautious. (Update: In the 2014 outbreak in which the number of deaths exceeds all of those seen up to 2013 by at least three-fold, they've lost nine individuals: http://news.yahoo.com/doctors-without-borders-loses-9-medics-ebola-125822963.html)
The myth that Ebola is “difficult to contract” is finally coming to end, and not a moment too soon. The meme that circulated on Facebook in September has finally stopped in its tracks (pun intended): the one we all probably saw that insinuated that the only way to contract Ebola is to be a grubby African rolling around in blood and vomit.
In fact, such memes never should have started if the world was really paying attention to reality instead of CDC and news media simplicity. An infectious disease group associated with the University of Minnesota recently called for the use of respirators in all Ebola healthcare workers, and said that while the disease is not technically airborne, it can be transmitted in aerosolized particles at short range (i.e. roughly 3-6 feet from an Ebola patient). I think most people are unaware that the CDC defines extended time in the 3-6 foot range of an Ebola patient as "direct contact." It makes sense as the case numbers increase that we see a minority of individuals who become infected in atypical fashion. The NBC reporter currently being treated for Ebola in Nebraska believes he was infected by helping to spray-wash a car in which an Ebola patient was transported.
Two months ago on August 7, Ken Isaacs, an executive with Samaritan’s Purse, an organization with 38 years’ experience in humanitarian relief, testified before Congress that containment of the outbreak was a failure, and that nothing short of an overwhelming response on the part of developed western nations would stop it. Here are a few quotes from his testimony:
“It’s not an issue of gloves and a mask, it’s an issue of no millimeter of skin can be exposed or you will get sick and most likely die.”
“If we do not fight and contain this disease in West Africa, we will be fighting and containing this disease in multiple other countries around the globe, and the truth is, the cat is most likely already out of the bag.”
“This is a very nasty, bloody disease. I could give you descriptions of people dying that you would not even believe.”
The only thing that hasn’t come true that Isaacs anticipated was a furious outbreak in Nigeria, which appears to have been completely stopped. How? I recently read an account of one of the Nigerian nurses who was infected with Ebola: not a single doctor or nurse would enter the isolation ward to care for them, and all materials for the patients were left outside of the isolation ward door.
On 9 September, Jonas Schmidt-Chanasit of the Bernhard Nocht Institute for Tropical Medicine announced that the containment fight in Sierra Leone and Liberia has already been “lost." WHO has further stated that if the disease is not adequately contained it could become endemic in West Africa, spreading as routinely as malaria or the flu.
Accounting for a recognized underreporting of 2.5-fold, current cases of Ebola in West Africa are at approximately 22,500. The case load going forward, assuming no rate change in transmission and a doubling of cases every two weeks, is estimated to be:
Oct. 27: 45,000
Dec. 8: 360,000
Jan. 5: 1.4 million (This is the same number as the CDC estimate, assuming no improvement in intervention or community behavior.)
Feb. 2: 5.7 million
Mar. 2: 23 million
The population of Guinea, Liberia, and Sierra Leone is a combined 22 million. Previous studies have shown that up to 25% of the population in West Africa already mysteriously has antibodies against Ebolaviruses. That's good news, but these countries could be more than decimated over the next six months. The CDC estimates that unless 70% of Ebola patients can be admitted to isolation wards, the outbreak will continue to grow. There are simply not enough beds: currently only around 20% of people are being treated in such wards. The rest are at home, or are being dumped into the street by their families, out of fear. Can you imagine? Ebola parasitizes our humanity in a way that few other diseases are capable of doing.
It’s very unlikely that the requisite Ebola isolation wards will be built in time. This means that transmission of the virus is dependent on the behavior of the citizens in West Africa to isolate themselves from infected family members. The larger the outbreak grows, the more difficult that will be to accomplish.
Many underdeveloped countries have already implemented travel restrictions from these 3 countries: they are well aware that their public healthcare infrastructure will not be able to handle this as well as western nations. Let’s hope that travel from West Africa to Asia isn’t that common, because once Ebola becomes entrenched in a densely packed urban area in an underdeveloped nation, it will be very difficult to stop.
I’ve seen many articles suggesting that Ebola isn’t much to worry about based on its transmissive characteristics. So, I decided to compare and contrast Ebola with other well-known pathogens to help us understand the difference.
Ebola characteristics
Let’s look at basic reproductive rate first, which is a number epidemiologists refer to as R0. For each infection, how many more infections will be caused in an unconfined chain of transmission?
Measles: 12-18
Whooping Cough: 12-17
Smallpox: 5-7
1918 influenza pandemic: 2.5
Ebola: 2.0-2.3
So far, it doesn’t look like Ebola is nearly as contagious as other pathogens.
Ebola also has a much longer incubation period. Instead of an incubation period of 2-3 days for flu, it has an incubation period of up to 21 days. This gives health workers the time to get a handle on the disease in early stages of an outbreak, and means much longer for an Ebola outbreak to grow.
How about infectious dose? This is where Ebola begins to get much scarier. For many bacterial diseases, the infectious dose of organisms required to get sick is in the thousands to hundreds of thousands, especially for pathogens our immune systems have co-evolved with for thousands of years. Even for many viral diseases like influenza, the infectious dose is in the hundreds of viral particles range. Not Ebola: the infectious dose of Ebola is only between 1 to 10 viral particles. So while Ebola is not very contagious, it is highly, highly infectious.
This is why working with Ebola patients is so dangerous. Wave one infected hand over your face, and you could very well be a goner, as the recent case in Dallas shows.
How else is Ebola different? In its animal reservoirs. Unfortunately, Ebola is incubated in a wide variety of mammalian reservoirs, from pigs to primates to dogs to bats. I don’t think we’ve even begun to study whether the disease could be vectored by arthropods. Viruses like smallpox and measles have no animal reservoirs that we know of, so despite being highly contagious, they’ve been relatively easy to eradicate from human populations because humans are the only organisms one needs to worry about in breaking the chain of transmission.
Finally, where Ebola stands out most starkly is in its fatality rate. For the current outbreak, that’s around 70%, and possibly less with good supportive medical care, but no one knows the exact figure.
I think most people would be highly surprised at how deadly Ebola is in comparison to other organisms. Take a look:
Scarlet fever and strep throat (caused by the same organism)
1912 Incidence: 0.15%
1961 Incidence: 0.18%
1912 Fatality: 4%
1961 Fatality: 0.05%
Measles
1912 Incidence: 0.3%
1955 Incidence: 0.3%
1912 Fatality: 2.32%
1955 Fatality: 0.06%
Whooping Cough
1922 Incidence: 0.1%
1960 Incidence: 0.0001%
1922 Fatality: 6%
1960 Fatality: 1.2%
Typhoid
1912 Incidence: 0.8%
1952 Incidence: 0.0015%
1912 Fatality: 20%
1952 Fatality: 7%
Tuberculosis
1930 Incidence: 0.1%
1970 Incidence: 0.002%
1930 Fatality: 70%
1970 Fatality: 11%
Smallpox, early 1900s
Incidence difficult to calculate
Fatality: 1%-30%: lower end of the range for most outbreaks in the “developed" world (variola minor); upper end of the range for most outbreaks in the “undeveloped" world (variola major)
The most fatal diseases in recent memory were smallpox and the 1918 influenza, which killed anywhere from 25 to 50 million people, a full 4-6% of the global population. Does Ebola have the capacity to become this level of a global killer? It depends on whether the disease migrates to other underdeveloped nations, and to what extent it becomes endemic in the human population in West Africa.
In summary, what’s concerning about Ebola is that case numbers are doubling in West Africa every two weeks, that the disease is capable of being vectored by a wide variety of mammals, and that the current circulating strain has a roughly 70% fatality rate, when you account for delays in deaths after cases are identified. We don’t yet know what the fatality rate is with good supportive care, but even if it’s only around 30%, that would make it on par with the highest fatality rates in human history, including smallpox (30%), bubonic plague (30%), and the 1918 influenza (20%).
Although I'm not terribly concerned about a growing outbreak of Ebola in the United States, the idea that it could become endemic in the North American wildlife population is also quite concerning, especially the government has apparently no intention of cutting off travel from affected countries, or placing those traveling from such countries in quarantine. Remember all the Ebola vomit power-washed into the Dallas sewer system?
If Ebola wipes out just half of the population of Guinea, Liberia, and Sierra Leone, or around 11 million people, Ebola will have killed around half as many people as the entire HIV pandemic has killed in all of history.
Many of these people won’t die of Ebola: they’ll die because of the economic and political disruptions that cause famines. If that weren’t bad enough, any area in which Ebola becomes endemic would then be ripe for the rise of political takeovers by Islamist or other extremist groups.
Also, if Ebola spreads beyond these three countries and becomes entrenched in urban areas that are underdeveloped, I think it could have the potential of killing as many people as the 1918 influenza pandemic or the Black Death. If we fail to contain the disease in West Africa, this has the capability of becoming an extremely serious pandemic. It's also a horrible way to die. Let’s hope that doesn’t happen.
Death tolls of famous epidemics:
Hong Kong Flu 1968-1969: 1 million
Cholera from 1817 onward: 3 million
HIV: 25 million
1918 flu: 50-100 million
Black Death 1300s to 1700s: 75 million
Smallpox: 300+ million
https://www.facebook.com/notes/monica-hughes/why-im-concerned-about-ebola/10153291620477846 |
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