Even the CDC Isn't Totally Sold on its Own Proclamations on How Ebola Is Transmitted
Today in multiple stories, our only and always comforting local daily, The Dallas Morning News, reiterates the official public line of the U.S. Centers for Disease Control: that physical contact with a person suffering symptoms of Ebola disease is the only mechanism of transmission by which the Ebola virus can infect a human being.
commons.wikipedia This is the official portrait of CDC Director Thomas Frieden. Maybe we need to ask for a little more than that.
That's not untrue. But it falls short of the full truth.
A more careful look at the CDC's own pronouncements and at recent research in respected journals shows that "viable" (living) Ebola virus can survive for days on surfaces outside the body. And it shows that little is known about the ability of "environmental" (outside the body) Ebola virus to infect.
That doesn't mean anybody's lying. But it does indicate that the CDC and some media (wouldn't you know it, our local) are more interested in crowd control than in digging for the full story.
In a story today with the wildly premature headline, "No additional suspected Ebola cases identified," The News assures readers that "Ebola can only be spread through direct contact with an infected person's bodily fluids, including saliva, urine or blood."
The paper cites CDC director Thomas Frieden as its authority, and, indeed, that's one version of the CDC's official line. A CDC bulletin on-line spells it out in more detail: "Direct contact means that body fluids (blood, saliva, mucus, vomit, urine, or feces) from an infected person (alive or dead) have touched someone's eyes, nose, or mouth or an open cut, wound, or abrasion."
But in another of its own online bulletins, the CDC lists an additional possible mechanism of transmission: "objects (like needles and syringes) that have been contaminated with the virus."
The thing about "objects" is that an almost infinite variety of them can serve as "fomites" or surfaces capable of carrying the living virus for some time. The Public Health Agency of Canada has reported that Ebola-type viruses "have been reported capable to ... survive on contaminated surfaces, particularly at low temperatures. One study could not recover any Ebolavirus from experimentally contaminated surfaces (plastic, metal or glass) at room temperature. In another study, Ebolavirus dried onto glass, polymeric silicone rubber, or painted aluminum alloy is able to survive in the dark for several hours under ambient conditions ... but is less stable than some other viral hemorrhagic fevers.
"When dried in tissue culture media onto glass and stored at 4 °C 9 (about 40 degrees Fahrenheit - my note), Zaire Ebolavirus survived for over 50 days."
The Canadian bulletin concludes: "A study on transmission of ebolavirus from fomites in an isolation ward concludes that the risk of transmission is low when recommended infection control guidelines for viral hemorrhagic fevers are followed."
The Canadian bulletin is based in part on research published in 2010 in the Journal of Applied Microbiology, which found that Zaire Ebola virus, "can survive for long periods in different liquid media and can also be recovered from plastic and glass surfaces at low temperatures for over 3 weeks."
Another CDC bulletin, "Interim Guidance for Environmental Infection Control in Hospitals for Ebola Virus," says, "Ebola on dried on surfaces such as doorknobs and countertops can survive for several hours."
I could find no paper or bulletin that said Ebola virus on a surface or fomite, even though viable, can infect a human being. But that doesn't mean science has proved it can't. It only means science hasn't settled the question.
Yet another CDC bulletin, "Interim Guidance for Environmental Infection Control in Hospitals for Ebola Virus," says, "The role of the environment in transmission has not been established. Limited laboratory studies under favorable conditions indicate that Ebola virus can remain viable on solid surfaces, with concentrations falling slowly over several days."
It's notable that the CDC's own protocols -- aggressive decontamination or incineration of materials that have come in contact with an infectious person -- seem to assume that a viable virus on fomites is a risk.
The CDC bulletin on hospital environments says: "There is no epidemiologic evidence of Ebola virus transmission via either the environment or fomites that could become contaminated during patient care (e.g., bed rails, door knobs, laundry). However, given the apparent low infectious dose, potential of high virus titers (concentrations) in the blood of ill patients, and disease severity, higher levels of precaution are warranted to reduce thepotential risk posed by contaminated surfaces in the patient care environment."
Hospitals are one thing. What about homes? A 2007 article in The Journals of Infectious Diseases concluded that disinfection protocols in dedicated hospital isolation wards probably kill off any virus that may have escaped to a surface, but the same article also said, "The risk from environmental contamination and fomites might vary in the household or other settings where decontamination would be less frequent and thorough, especially if linens or other household materials were to become visibly soiled by blood."
Ebola has arrived in our city. We should be asking all of the questions we can think of pertaining to every single aspect of the disease and demanding the very best answers we can get. Of course we want to know what is known, but we also need to know the known unknowns.
In its lead editorial today, The Morning News barely mentions the issue of red flags that should have been raised when a traveler from Africa first showed up sick at a Dallas hospital, but the paper then says immediately, "Let's leave those concerns for another day."
Let's not.
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