On Saturday, President Obama stated that “Ebola is actually a difficult disease to catch. It’s not transmitted through the air like the flu.”
Dr. Tom Frieden, director of the Centers for Disease Control and Prevention (CDC), also said that “this is not like flu. It’s not like measles, not like the common cold. It’s not as spreadable, it’s not as infectious as those conditions.”
But after reviewing the scientific literature, Dr. Lisa Brosseau and Dr. Rachael Jones found little evidence that the deadly hemorrhagic fever can only be caught through direct contact with the bodily fluids of an infected person.
The CDC and the World Health Organization “speak very loudly and say very strongly it isn't airborne, but they don't offer a lot of support for that. And I will tell you when I look for the data, there is not a lot of data to support their contention that it isn't an aerosol-transmissible disease,” said Brousseau, who explained the difference between “aerosol transmission” and “airborne transmission”.
“We believe there is scientific and epidemiologic evidence that Ebola virus has the potential to be transmitted via infectious aerosol particles both near and at a distance from infected patients, which means that healthcare workers should be wearing respirators, not facemasks,” Brousseau and Jones stated in a guest commentary published in September by the University of Minnesota’s Center for Infectious Disease Research and Policy (CIDRAP).
Brousseau and Jones, who CIDRAP described as “national experts on respiratory protection and infectious disease transmission,” pointed out that “most scientific and medical personnel, along with public health organizations, have been unequivocal in their statements that Ebola can be transmitted only by direct contact with virus-laded fluids, and that the only modes of transmission we should be concerned with are those termed ‘droplet’ and ‘contact’.”
But this “reflects an incorrect and outmoded understanding of infectious aerosols… virus-laden bodily fluids may be aerosolized and inhaled while a person is in proximity to an infectious person,” they wrote.
Unlike HIV, which “is primarily a bloodborne pathogen with low probability for transmission via aerosols,” the “Ebola virus, on the other hand, is a broader-acting and more non-specific pathogen that can impede the proper functioning of macrophages [white blood cells] and dendritic cells—immune response cells located throughout the epithelium [skin and mucous membranes].
”Epithelial tissues are found throughout the body, including in the respiratory tract. Ebola prevents these cells from carrying out their antiviral functions but does not interfere with the initial inflammatory response, which attracts additional cells to the infection site. The latter contribute to further dissemination of the virus and similar adverse consequences far beyond the initial infection site.”
Healthcare workers should be equipped with air-purifying respirators because “patients and procedures generate aerosols, and Ebola virus remains viable in aerosols for up to 90 minutes,” they noted.
“For a risk group 4 [high individual and community risk] organism like Ebola, the minimum level of protection should be an N95 filtering facepiece respirator,” which filters out 95 percent of all airborne particles, according to the CDC.
However, Brousseau and Jones say their risk assessment found that “for healthcare workers caring for many patients in an epidemic situation, this type of respirator may not provide an adequate level of protection….
"If we assume the highest generation rate (4) and a standard patient room, a respirator with an APF (assigned protection factor) of at least 50 is needed" because coughing, sneezing, vomiting, and even flushing a toilet can emit “a pathogen-laden aerosole that disperses in the air.”
They also cited a study published in the Dec. 23, 1995 edition of The Lancet and abstracted by the National Institutes of Health (NIH) entitled: “Transmission of Ebola virus (Zaire strain) to uninfected control monkeys in a biocontainment laboratory.”
That study’s authors reported “transmission of Ebola virus (Zaire strain) to two of three control rhesus monkeys (Macaca mulatta) that did not have direct contact with experimentally inoculated monkeys held in the same room.”
“The two control monkeys died from Ebola virus infections at 10 and 11 days after the last experimentally inoculated monkey died. The most likely route of infection of the control monkeys was aerosol, or conjunctival exposure to virus-laden droplets secreted or excreted from the experimentally inoculated monkeys. These observations suggest approaches to the study of routes of transmission to and among humans.”
In a more recent Nature article published on Nov. 15, 2012, other researchers reported that “piglets inoculated oro-nasally with ZEBOV [Zaire strain of Ebola] were transferred to [a] room housing macaques in an open inaccessible cage system. All macaques became infected” with Ebola despite the fact that they had no “direct contact” with the piglets.
“Infection of all four macaques in an environment preventing direct contact between the two species and between the macaques themselves supports the concept of airborne transmission,” the study authors wrote.
However, in the same statement, CIDRAP said that “the commentary addresses potential modes of transmission for Ebola in healthcare settings and discusses the implications for optimal respiratory protection for healthcare workers. CIDRAP concludes that the commentary is based on sound science and believes it is an important consideration in the safety of healthcare workers who provide care to Ebola patients.”
A day earlier, CIDRAP’s director, Dr. Michael Osterholm, told CNN that the possibility that Ebola could be transmitted by air was “the single greatest concern I’ve ever had in my 40-year public health career. I can't imagine anything in my career -- and this includes HIV -- that would be more devastating to the world than a respiratory transmissible Ebola virus.”
CNSNews.com contacted CIDRAP to ask why it published an article discussing the need to protect healthcare workers from the possible aerosole transmission of Ebola if, as President Obama and Dr. Frieden maintain, the virus cannot be caught this way.
But CIDRAP media relations coordinator Caroline Marin responded that Osterholm was the only one who could answer such questions, adding that “I don’t know when he will be available” to do so.