The question of why the Ebola virus seems to so badly frighten so many people seems, at first, to have an obvious answer.
Ebola, after all, is an incurable hemorrhagic virus with a mortality rate that soars in some outbreaks to 90 percent of those infected. Symptoms in sufferers with advanced disease go beyond high fever and gastrointestinal misery to bleeding from the mouth, nose, ears and eyes.
As NPR has reported, the current outbreak centered in West Africa features a mounting death toll coupled with a geographic spread from its epicenter. This is a frightening situation for people who live in, or who have recently visited, West Africa — and it is those people who deserve the great bulk of our concern, our compassion, and our medical and humanitarian resources.
But the fears for our personal safety here in the United States that I have encountered on social media seem to run out of all proportion to any reasonable assessment of risk. These worries, of course, relate in part to the arrival in Atlanta of two American medical workers infected with Ebola while in Liberia — Kent Brantly and Nancy Writebol — who remain under supportive care at Emory University Hospital.
By no means is this anxiety the universal response to Brantly's and Writebol's arrivals home. When Donald Trump tweeted last week that we should "KEEP THEM OUT OF HERE," a backlash ensued.
But enough people do react with fear and suspicion to make it notable. A flavor of such comments can be found at the end of this article. And on my Facebook timeline this past weekend appeared a thread in which more than a few people worried about their family members' safety as they caught planes at Atlanta's Hartsfield-Jackson airport or went about their business in the city or its suburbs.
In both places — NPR and Facebook — people pointed to findings from a 2012 paper in Nature that show Ebola transmission from experimentally infected captive pigs to previously uninfected monkeys without direct physical contact. To some, this means we Americans are at alarming risk now that people sick with Ebola are in the U.S.
Scientific data tell us that these extreme fears are misplaced.
The plane carrying Brantly home from Liberia on Saturday, and his colleague Writebol on Tuesday, didn't fly into the ultrabusy Hartsfield airport but instead to Dobbins Air Reserve Base. Each patient went from the isolation pod in the specially rigged private plane to a protected ambulance and then, wearing isolation suits, into the isolation unit in Emory University Hospital.
Yes, there's a pattern here: isolation! It's not reasonable to think that anyone in the Atlanta metro area was exposed to the Ebola virus as a result of the Americans' return home. Maryn McKenna's piece in Wired on Monday makes excellent reading for its calm assessment of the situation from someone who knows the science-of-epidemiology beat.
But what of the pig-to-monkey transmission without direct physical contact? When hospitalized Ebola patients are no longer in protective suits, to what degree are others in the same room at risk?
And thinking more broadly — still in context of the Nature paper — what about people flying commercially from West Africa into the U.S.? Even when there's no physical contact with other passengers (or people on the ground), could people who fall ill as they come into the country pose a grave risk to public health here?
Quick to alleviate these concerns, McKenna writes:
"Contracting [Ebola] requires direct contact with the bodily fluids — blood, feces, vomit — of someone who is symptomatic with the disease. You cannot catch Ebola from someone who is incubating it but not symptomatic; and you cannot catch it from simply being in the same room as someone who has it. (If you're going to quote back to me the infamous 'airborne Ebola' paper from 2012, don't bother. Six pigs, four monkeys, engineered lab conditions: no relevance to any real-world situation in a household or a hospital.)"
Well, yes, what McKenna says makes sense. Still, no epidemiology expert myself, I needed to dig deeper on the topic of airborne transmission. I sent a shout-out to my Twitter universe for expert help and connected with a virologist from Queensland University in Australia, Dr. Ian McKay.
McKay had this to say, via email, about the pig-monkey Nature paper:
"More study needs to be done, or clarification made, of the risk for airborne spread, but we do know that the major risk is one of direct contact rather than with submicron aerosols of the kind involved in cold and flu transmission. These are NOT in play with Ebola ...
"World Health Organization guidance acknowledges a risk due to coughing. But this is not the same as an aerosol. As an example, an aerosol can travel around corners, droplets cannot. Big wet droplets, which don't travel far, are in the mix as a risk factor when close to very ill patients, but submicron particles that hang in the air for a long time (up to 4 minutes in one example) and can travel, are not in the mix as a source of acquisition of the Zaire Ebola virus in the field.
"To support [a suggestion of airborne transmission for Ebola] you would obviously see much greater numbers of cases and a higher rate of spread if this was able to be spread by aerosol (think an endemic influenza or common cold's rhinovirus)."
So, according to McKay, we don't have to worry about Ebola spreading in aerosol form the way that cold and flu germs do. We shouldn't assume a non-zero risk from very close contact with very ill patients. That's sobering, but it's important to remember that we are in no way seeing a transmission pattern in the current outbreak that supports airborne transmission, even in the droplet form.
But the question of why Ebola terrifies lingers. On this, McKay says:
"Ebola can, in under half of cases, make infected people bleed very obviously. I think the average human may be wet-wired to have a very gut response to that. Then you have a number of scary (and mostly unrealistic) movie representations of Ebola and Ebola-like virus outbreaks, and that doesn't help. When the same thing seems to appear in the real world, the reaction is fairly predictable. Good, clear and concise information about risks is what's needed. Perhaps more experts in Ebola getting engaged with the world would be a help to the public, too."
I think McKay is on to something with his "wet-wired" comment. We Homo sapiens have evolved over millennia to be vigilant for clear and present dangers. Ebola, when it causes advanced illness, certainly falls under that category in the present day, much as predators like cave bears or big cats did for our ancestors in eons past.
We have a tendency — nothing hard and fast, nothing deterministic — under certain circumstances, like an international outbreak with alarmist aspects regarding public health in the U.S., to see the havoc something like Ebola may cause and respond with emotions ranging from worry to panic, even well outside the danger zone.
It may help to recognize this tendency and to know that we can calm the visceral storm, step back, reread the facts, and respond with resources and compassion to those who are truly at risk or already suffering.