David Sanders, Dr. Devi Nampiaparampil, and Dr. Sanjay Gupta debate the likelihood that Ebola could go airborne.
SCIENTISTS ARGUE EBOLA MIGHT ALREADY BE CONTAGIOUS VIA AIRBORNE METHODS — AEROSOLS WITH VIABLE VIRUS
CIDRAP (The Center for Infectious Disease Research and Policy is an epidemiologic research and publishing center within the University of Minnesota that focuses on addressing public health preparedness and emerging infectious disease response.
On September 17, 2014 — one week before “Patient Zero” Thomas Eric Duncan arrived in the United States from Liberia, West Africa — Lisa M Brosseau, ScD, and Rachael Jones, PhD published a warning that health care workers need optimal respiratory protection for their protection from the Ebola virus. Both are national experts on respiratory protection and infectious disease transmission.
Both experts 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.
Respirators, not facemasks: That means air tight seals between the health care workers respiratory system and the environment where they are caring for their Ebola patient. They emphasize using a powered air-purifying respirator (PAPR) with a hood or helmet, because it offers many advantages over an N95 filtering facepiece or similar respirator, being more protective, comfortable, and cost-effective in the long run.
The experts strongly urge the US Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO) to seek funds for the purchase and transport of PAPRs to all healthcare workers currently fighting the battle against Ebola throughout Africa—- and beyond.
Dr Brosseau and Dr Jones say 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-laden fluids, and that the only modes of transmission we should be concerned with are those termed “droplet” and “contact.” Tuesday night on Fox News, CDC Director Dr. Tom Frieden said we know how Ebola spreads. He says it only spreads by direct contact. Kelly skeptically asked if Frieden would go into an infected Ebola patient’s room without covering his head, and while wearing only one pair of gloves and with his feet exposed. Dr. Frieden answered yes.
Dr Brosseau and Dr Jones believe the “direct contact” belief reflects an incorrect and outmoded understanding of infectious aerosols. They report that modern research has shown that aerosols emitted from the respiratory tract contain a wide distribution of particle sizes—including many that are small enough to be inhaled. They say both small and large particles will be present near an infectious person.
Dr Brosseau and Dr Jones report particles as large as 100 mcm (and perhaps even larger) can be inhaled into the mouth and nose. Larger particles are deposited in the nasal passages, pharynx, and upper regions of the lungs, while smaller particles are more likely to deposit in the lower, alveolar regions of the lungs. And for many pathogens, infection is possible regardless of the particle size or deposition site — mouth, nose, throat or lungs. The scientists report the primary portal or portals of entry of Ebola into susceptible hosts have not been identified. Experts do know that Ebola prevents epithelial cells (including those in the respiratory tract) from completing their antiviral functions, but the Ebola virus does not interfere with the initial inflammatory response, which attracts additional cells to the infection site. The gathering of immune-fighting cells as part of the inflammatory response actually result in those cells moving on to disseminate the virus to other parts of the body with its known harmful and fatal results. Dr Brosseau and Dr Jones explain that experimental studies have demonstrated that it is possible to infect non-human primates and other mammals with filovirus aerosols. Ebola virus is a member of the filovirus family.
Dr Brosseau and Dr Jones explain that body fluids, such as vomit, diarrhea, blood, and saliva, are capable of creating inhalable aerosol particles in the immediate vicinity of an infected person. Cough was identified among some cases in a 1995 outbreak in Kikwit, Democratic Republic of the Congo, and coughs are known to emit viruses in particles that can be inhaled by people that are near the patient. Vomiting produces an aerosol and has been implicated in airborne transmission of gastrointestinal viruses that cause the stomach flu. They explain that diarrhea, even when contained by toilets can go aerosol when toilet flushing emits a pathogen-laden aerosol that disperses in the air.
Dr Brosseau and Dr Jones relate this information to the known fact that the Ebola virus has been found in the saliva, stool, breast milk, semen, and blood of infected persons.
Dr Brosseau and Dr Jones report that aerosolized Ebola virus was discovered to have a 3.06% per minute decay rate in air at 72°F with 50% to 55% humidity. That means that Ebola would be at a 99% loss while floating in the air for 104 minutes. They also reported that particles can take up to an hour to settle in still air, and with air currents Ebola virus can be transported considerable distances before settling on a surface. The virus could not be recovered from glass, metal or plastic surfaces.
Dr Brosseau and Dr Jones explain that persons with no known direct contact with Ebola virus disease patients or their bodily fluids have become infected, which considering the information above, it leads one to conclude it is more likely Ebola is transmitted by inhaling infected aerosol than by touching glass, metal or plastic where the virus may have settled and become inactive.
Dr Brosseau and Dr Jones submit that the “direct contact” method of Ebola transmission is more likely, but that under the right conditions that Ebola transmission may occur from inhalation of aerosols. This could also explain the inconsistent pattern where some people get infected and some do not. A health care professional’s fate could be left to chance on whether a viable aerosol passes around a splash-protecting face shield or an unsealed N95 mask — and connects with vulnerable tissue of the health care professional.
Dr Brosseau is a Professor and Dr Jones an Assistant Professor in the School of Public Health, Division of Environmental and Occupational Health Sciences, at the University of Illinois at Chicago.
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CIDRAP COMMENTARY: Health workers need optimal respiratory protection for Ebola
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