Health experts and officials are still confident that an Ebola outbreak here in America is highly unlikely, considering you must come into contact with a sick person's bodily fluids in order to be infected.
But now that the first case has been diagnosed in New York City -- an objectively population-dense city, where there are nearly 7.7 million passengers riding on subways and buses on the average weekday -- the question arises: Are New Yorkers, who live in a more public transportation-reliant city, more at risk for Ebola than residents of a city like Dallas, a (comparatively) sprawling city with a more definitive car culture, where the first Ebola patient was diagnosed in the U.S.?
Not necessarily, because of the manner in which Ebola is spread, says A. Scott Lea, M.D., an associate professor of infectious disease at the University of Texas Medical Branch in Galveston, Texas, whose lab has been doing Ebola research for the last 10 years.
That's mainly because Ebola is not airborne like the flu. With "influenza, the viral particles are able to exist in the air and are very contagious, and anyone who walks through the room [might] get that particular disease," Lea told HuffPost. "That is not known to occur with Ebola."
How Ebola is transmitted is via contact with a symptomatic person's blood and bodily fluids, like vomit, feces or sweat. Theoretically, if you had an Ebola patient who was hemorrhaging and spraying the air with his or her droplets, yes, you could catch Ebola, Lea said. But the place where a scenario like that would happen would likely not be a public setting; that's something that happens, for instance, when you're intubating someone in an intensive care unit in a hospital, he said.
In addition, when a person has Ebola, that person is typically knocked down -- it's not a case of the "walking wounded," Lea said. "With influenza, you may get sick and feel bad, but some people go to work and cough in the air. But this does not happen with Ebola -- if you have Ebola, you're down," he said. Meanwhile, if someone is symptomatic with Ebola, he or she likely won't be "well enough to be on a subway in a hustle-bustle society like [New York City]."
Even if a person with Ebola were to somehow find him or herself on a crowded subway car, and that person's saliva were to somehow make it onto a pole, and then onto another passenger's hand, that saliva has lower levels of virus in it than a symptomatic infected person's blood, vomit or feces, according to the World Health Organization (though the WHO does note that saliva and tears may carry some risk). "In studies of saliva," the WHO notes, "the virus was found most frequently in patients at a severe stage of illness. The whole live virus has never been isolated from sweat."
That's precisely why in any sort of city -- whether it's a sprawling, car-heavy city like Dallas or a population-dense, subway-dependent city like New York -- the people who would be most at risk for Ebola would be the family members of the Ebola patient (who would presumably live and have the closest contact with the patient while he or she was symptomatic, as well as the highest risk of coming into contact with his or her bodily fluids), or health care workers caring for the Ebola patient.
Plus, as The New York Times noted, there has never been a confirmed case of Ebola transmission from a dry surface to a human. (The New York Times also pointed out that there have been no known instances of Ebola transmission on public transportation -- particularly noting that Africa is not short of buses and trains -- and that even Patrick Sawyer, the Liberian-American who was sick with Ebola and vomiting while on a plane, did not infect anyone else on the flight.)
Anyone who comes into contact with an Ebola patient before he or she is symptomatic is at very low risk, Lea said. That's because the viral load of a person who is not displaying symptoms is very low. It gets higher as symptoms develop and progress, and the higher the viral load, the more contagious a person is. That's why, in the West African countries that are experiencing the bulk of the Ebola outbreak, it's the family members, health care workers and funeral workers who are at high risk of infection, Lea said.
That's also why you cannot reliably test a person for Ebola until he or she is displaying symptoms, CDC Director Dr. Tom Frieden previously explained. "You can't spread Ebola until you have symptoms and you can't test for it until there are symptoms," Frieden said. "In fact, when Ebola first comes on, the amount of virus that a person sheds is very low. So initially, a test may even be negative for someone with initial fever. As someone gets sicker and sicker, you get more and more infectious, because there's more virus in their body."
Like in Dallas, when Thomas Eric Duncan was diagnosed with Ebola, "disease detectives" have been dispatched in New York City to find people who may have had contact with Spencer and to weigh their level of risk for Ebola from that contact. New York City Mayor Bill de Blasio said in a press conference Friday that these "disease detectives" are actually "experts who act as detectives would in a police investigation -- [they] trace all contacts the patient has had, ... retracing all the steps of the patient." That involves accounting for every minute of Spencer's time since he was deemed to be a potential risk. So far, officials have identified four individuals who Spencer had contact with -- and one of them, the driver of the car service that Spencer used -- has been cleared because he didn't have any direct contact with Spencer. The other three, one of whom is Spencer's fiancée, are currently in isolation.
And just like in Dallas, when a hired crew cleaned the apartment where Duncan stayed, a city-contracted crew also cleaned Spencer's apartment. Even though there is not believed to be any bodily fluids in the apartment, "our contractor will clean and disinfect out of an abundance of caution. They will throw away the bed linens, towels, toiletries, food in the fridge, throw away garbage," a health department spokesperson told ABC 7 News. "They will wipe down hard, frequently touched surfaces with disinfectant. And once complete, we will inspect and certify the apartment is OK to re-enter."