Should You Worry About the Ebola Outbreak?
Ask Science explains what exactly Ebola is, and breaks down some of the misinformation being spread by news outlets.Â
By now, you’re probably either sick of hearing about Ebola, or terrified to leave your house. While it’s true that Ebola is a pretty horrible disease, you might be surprised to know just how much misinformation there is out in the media about the current outbreak.
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Airborne vs Airborne
Airborne vs AirborneOne of the big areas of confusion is whether or not Ebola can be spread by “airborne transmission.” One reason for this confusion is that not everyone means the same thing when they say “airborne transmission.”
To many epidemiologists (people that study diseases and how they spread), “airborne transmission” means that a pathogen can survive for long periods of time in the air. For example, the flu virus can float around in the air for two days or longer. If you have the flu, and go sneeze in the closet, and then your friend goes into that closet the next day, there’s a chance he could get the flu.
In contrast, some people refer to “airborne transmission” as meaning, “you can get sick if a sick person sneezes on you directly.”
Many media websites are spreading the report that some people are suspicious that Ebola could be spread by airborne transmission–but which kind of airborne are they talking about, and is it true?
If you read the “Ebola and airborne transmission” studies that are mentioned in the news (which I’m willing to bet most news writers haven’t), nearly every study cited that discusses the possibility of airborne transmission points to a study done in 1995 on some monkeys.
In that study, there were some monkeys that had Ebola sitting in cages on one side of the room, and some monkeys that didn’t have Ebola sitting in cages on the other side of the room. At a certain point, the scientists noticed that two of the Ebola-free monkeys had somehow caught Ebola.
Before you go out and buy a gas mask, though, pay attention to the discussion section of the paper, in which the scientists state that the monkeys were most likely infected by eating the “secretions or excretions” of the infected monkeys, or rubbing it into their eyes. Nowhere do they state that this infection occured by simply breathing the same air as the sick monkeys.
A more recent study that is sometimes pointed to (but not actually read) by the news media shows that there is a “suspicion that the virus was transmitted by airborne particles.”
However, this wasn’t because the study showed any proof of that, but because out of the 315 cases they looked at, 12 of the people couldn’t figure out where they were exposed. The study goes on to say that there have never been any reports of airborne exposure of Ebola in humans, and that the only evidence ever of this is between monkeys in laboratories. They then cite the one study I mentioned earlier.
So, yes–if someone with Ebola sneezes on you, or throws their excretions into your eye, there is a chance you’ll get Ebola. If someone with Ebola in the sporting good aisle of Wal-Mart sneezes on a basketball, and you’re over in hardware, there is zero chance you’ll catch Ebola. (Unless you run and grab that basketball and rub it on your eye, which you probably shouldn’t do even if the sneezer didn’t have Ebola.)
There’s Something in the Air
The influenza virus can survive for two days or longer floating around in the air. Some media outlets are reporting that Ebola can survive several days outside of a host. Most of these “facts” come from places like the MSDS pathogen safety data sheet for Ebola. If you read that document, you’ll see it says: “SURVIVAL OUTSIDE HOST: The virus can survive in liquid or dried material for a number of days (23).”
But that little number 23 doesn’t mean Ebola can survive for 23 days. Instead, it refers to footnote number 23, which points to a study where this information supposedly came from.
Once again, if you read the actual study, you’ll find that it says that the virus can exist in dead ape carcasses for only several days.
Every other website that has exact figures for survivability “outside of the host” just copies the same exact text. (See this one, for example.)
I’m not aware of any actual studies showing that Ebola can survive for any significant time outside of a host.
Keeping it in Perspective
Keeping it in PerspectiveAnother thing to keep in mind are the statistics of Ebola. Even in Africa, Ebola is hardly the biggest threat to human health. Last year, 130,000 people died from measles, another 60,000 from tetanus, 750,000 died from dysentery, and a staggering 1.17 million from malaria. The CDC reports that every year, 250,000 to 500,000 people die from the flu. Meanwhile Ebola (at the time of this writing) has resulted in less than 1,000 deaths so far in 2014.
While all pathogen-related death is tragic, you’re much more likely to die from flu, dysentery, or measles than you are Ebola. So before you head off to your underground Ebola shelter, think about stopping by the drugstore to get your flu shot.
What Makes Ebola so Scary?
Aside from the fact that it has pretty horrific symptoms and a relatively high mortality rate, one of the main things that makes Ebola dangerous is that we don’t know where its natural reservoir is. The natural reservoir of a pathogen is where it lives when it’s not infecting humans.
For example, we know that malaria inhabits, but doesn’t kill, mosquitos. It can live inside mosquitos for a long time, and then spread to humans through mosquito bites. Rabies lives inside of bats, foxes, raccoons, and skunks when it isn’t causing trouble for humans. Cholera lives quite happily in plankton and shellfish, doing neither creature any harm.
But nobody is sure where Ebola lives when it isn’t infecting humans. Fruit bats and certain types of monkeys are a couple of likely sources. A less likely source is a certain type of crab that gets eaten by a certain type of monkey.
The reason malaria isn’t an issue in the US is because we know the natural reservoir (mosquitos), and for a long time have taken measures to counteract that fact (with window screens, treating standing water, etc.) But since we don’t understand where Ebola comes from, we don’t know what to do to prevent Ebola outbreaks.
Conclusion
ConclusionIf you liked today’s episode, you can become a fan of Ask Science on Facebook or follow me on Twitter, where I’m @QDTeinstein. If you have a question that you’d like to see on a future episode, send me an email at everydayeinstein@quickanddirtytips.com.create new email
Photos of Africa and Ebola map, Scientist, and Sneezing woman courtesy of Shutterstock.
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About the Author
Dr. Lee Falin earned a B.S. in Computer Science from the University of Illinois, then went on to obtain a Ph.D. in Genetics, Bioinformatics, and Computational Biology from Virginia Tech.Â
