Air Media Magazine, Winter 2015
By Bill Palmer, CAFS, CEICC and Hector Valtierra, M.A., M.S. MPH

Two of the most beloved film genres are horror movies and conspiracy theory thrillers. In a horror film it is usually very clear who the antagonist is and he is often some combination of misunderstood and unstoppable. The antagonist in the horror movie is frequently a mysterious and gruesome killer. In conspiracy theory movies a government or large corporation is often seen as hiding important information from the general public in order to best serve the needs of those who are in power.

The recent import of Ebola virus into the U.S. and the infection of healthcare staff caring for Ebola patients set off a wave of near panic in the hearts of many. The fear and mistrust elicited by presence of Ebola in the U.S. was worthy of the best horror or conspiracy theory movie that Hollywood could conjure up. Ebola is misunderstood by much of the population and the perception of many is that it is a mysterious and unstoppable killer. This lack of understanding, coupled with some early missteps by health authorities, has led many to believe that the government isn’t being totally honest with the public about how Ebola is spread. The public also has the perception that the level of risk to the general population is being down played by those in charge. All of these fears are fanned by the fact that Ebola can be a gruesome killer.

As is often the case, the lack of familiarity with a topic may lead to unrealistic fear, anxiety and theories that impact our judgments and actions. It is our hope that through this article that we can quell some of the fear surrounding the Ebola issue and that we can arm you with sufficient facts so that you may best know how to respond to and help your clients.

Ebola Facts

    • First discovered in 1976 near the Ebola River
    • a rare disease in the family Filoviridae which causes hemorrhagic fever
    • Hemorrhagic fever diseases are those that are marked by severe bleeding (hemorrhage), organ failure, and many times death.
    • Can cause disease in humans and non-human primates.
    • Five subtypes of the disease (Ebola virus, Sudan virus, Tai Forrest virus, Bundibugyo virus and Reston virus). Reston virus is the only one of the five that has not caused infection in humans.
    • Spread through direct contact (through broken skin or unprotected mucous membranes in, for example, the eyes, nose, or mouth) with:
      • blood or body fluids (including but not limited to feces, saliva, sweat, urine, vomit, breast milk, and semen) of a person who is sick with Ebola
      • objects (like needles and syringes) that have been contaminated with the virus
    • infected fruit bats or primates (apes and monkeys)
    • Not spread through the air or by water, or in general, by food.
    • No evidence that mosquitos or other insects can transmit Ebola virus.

Geography and Epidemiology

Recent events surrounding the 2014 outbreak of Ebola virus in Western Africa (Fig. 1) and the resulting related cases in the U.S., have caused a great deal of anxiety and fear throughout the world. Three countries, Guinea, Sierra Leone, and Liberia are currently experiencing the worst Ebola epidemic ever seen. With a combined geographic area (165,625 mi2) that is slightly larger than the State of California (163,696 mi2) and a little more than half the population of California, each country has had unique setbacks in trying to control the epidemic.

Figure 1. Percentage of Ebola virus infection cases (not laboratory -confirmed) in three western African countries as reported by the U.S. Centers for Disease Control and Prevention (January – December 2014). Purple circles represent Ebola mortality rate for each country.
Figure 1. Percentage of Ebola virus infection cases (not laboratory confirmed) in three western African countries as reported by the U.S. Centers for Disease Control and Prevention (January – December 2014). Purple circles represent Ebola mortality rate for each country.

As can be seen, the mortality rate for each country varies significantly. It is interesting to note that the country with the fewest percentage of cases, Guinea, has the highest mortality rate from the disease. As of 2 December 2014, there have been 16,899 cases in all three countries (CDC, 2014). Countries that have also been infected by this epidemic with a relatively few number of cases include Mali (8 cases), Nigeria (20 cases), Senegal (1 case), Spain (1 case), and the U.S. (4 cases).

The United States has seen a few notable outbreaks since 2000. The Severe Acute Respiratory Syndrome (SARS virus) pandemic (2002-2003), Monkeypox virus (2003) in the Midwest, the avian influenza virus pandemic (2003 – 2004) and swine influenza virus pandemic (2009) have taken up considerable media coverage. As the reader will note, of the five pathogen classes (viruses, bacteria, fungi, protozoans, and helminths), viruses seem to be at the forefront of epidemics from previously unseen pathogens, i.e., emerging infectious diseases to the human population. Both the Biosafety in Microbiological and Biomedical Laboratories (NIH and CDC publication) and the World Health Organization’s Laboratory Biosafety Manual include pathogen stability in the environment as an essential component in conducting risk assessments for facilities.

Virus stability in the environment depends on the route-of-transmission (e.g., respiratory, sexually-transmitted, direct contact) as well as environmental conditions such as relative humidity and temperature. In addition, the dose of each virus species (or strain) must be considered when determining its pathogenicity. The concept of quantal infection, suggested by Wells (1955), is useful to the air filtration professional and infectious disease epidemiologist as a measurement tool where a quantum of infection is the number of infectious airborne particles (dose) required to produce infection in a susceptible host (Li et al., 2007).

Virus structure

The structure of any virus (singular, virion, a single virus particle) includes a nucleic acid (i.e., DNA or RNA). Each of these nucleic acids types contain the genes of the virus. Surrounding this nucleic acid is the protein coat (i.e., capsid or nucleocapsid) providing a layer of protection for the nucleic acid and its genes. Some viruses may even have another layer of lipids surrounding the protein coat. Inherent in a virion’s ability to enter into a host cell (i.e., human cells) are protein projections called protein spikes. Each cell type in the human body (e.g., nerve cells, muscle cells, respiratory epithelial cells, liver cells) has a set of unique-to-the-cell-type protein receptors. The viral protein spikes fit into the protein receptors like a lock and key thus allowing, and restricting, the virus to enter into a specific type of cell or relatively few cell types. Filoviruses are filamentous, enveloped, single-stranded, negative-sense RNA viruses. The family Filoviridae includes two distinct genera: marburgviruses and ebolaviruses, which differ in their glycoproteins (protein spikes) at both the nucleotide (nucleic acid) and amino acid (protein) levels. Their genomes have a length of approximately 19,000 base-pairs, which encodes seven structural proteins (Martines et al., 2014) (Fig. 2).

Figure 2. Ebola virion. Each virion is filamentous, or long and thread-like with a length that ranges from 0.8 µm to 1.4 µm. (Adapted from Ascenzi et al., 2008).
Figure 2. Ebola virion. Each virion is filamentous, or long and thread-like with a length that ranges from 0.8 µm to 1.4 µm. (Adapted from Ascenzi et al., 2008).

So what role can we play?

As filtration experts, this has raised many concerns regarding what we should be recommending to our healthcare customers to best protect their patients and staff. The conflict lays in the perception by some that the disease may be spread via the aerosol route. We would like to look at the facts of Ebola transmission and hopefully clear up some of the misconceptions.

Ebola Virus Aerosol Transmission Research

Case #1 – At least three studies (Johnson et al., 1995; Belanov et al., 1996; Twenhafel et al., 2012) have shown that, at least experimentally, Ebola virus can be transmitted via the aerosolized route. Rhesus macaques or Guinea pigs were placed inside chambers in a BSL-4 level laboratory. Ebola virus was then artificially aerosolized into the chamber. Animals developed Ebola infection as a result.

Misconception #1 – These studies show that Ebola virus can potentially be spread through the air. However, when interpreting any laboratory animal-model study, it is key to note is that, when artificially aerosolized, Ebola virus can be spread through the air to non human primates or rodents. These experiments were done in a laboratory and do not represent real life conditions. Ebola virus typically attacks the liver, kidneys and spleen in humans and non human primates. It does not typically cause disease in the lungs which would be a pre-requisite of generating infectious particulates capable of being spread via the airborne route.

Case #2 – In Richard Preston’s book, The Hot Zone, an outbreak of Ebola Reston virus was documented among a group of monkeys that were being held in a quarantine facility in Reston, VA. Many of the primates that were infected were not in close proximity to each other.

Misconception #2 – Many of the infected monkeys did not have close contact with each other and experts originally considered the possibility that the virus may have spread through the air. Further examination, however, concluded that the virus was spread to monkeys that were not near each as a result of the monkeys flinging fecal matter that was contaminated with the virus. It is also thought that the pressure washing of the animal cages may have contributed to the spread of the disease.

All research and epidemiology suggest that Ebola virus is not transmitted in humans via the aerosolized route, although it has been shown to be induced in non-human primates and guinea pigs under experimental conditions. A number of environmental factors affect the stability of viruses outside of the host including relative humidity and temperature. General reviews of virus survival on environmental surfaces can be found in Mahl & Sadler, 1975; Sattar & Springthorpe, 1996; Kramer et al., 2006; Valtierra, 2008. Although viruses do have a natural route-of-infection, working with viruses in laboratories introduces events such as centrifuging that may aerosolize virus in much higher titers than normally seen in a natural infection. In such cases, even Rabies virus has been shown to be transmitted via inhalation in a lab whereas the normal route-of-infection is being bitten by a rabid animal (Winkler et al., 1973). Potentially lethal viruses without effective vaccines or FDA-approved anti-viral therapeutics or with the possibility of artificial aerosolization are therefore worked at in Biosafety Level-3 (BSL-3) and BSL-4 laboratories.


One of the most important roles we can play at this time is to provide accurate educational information to our clients and lead them based on a logical assessment of risk based on facts. There are many people that are misinforming their clients based on inaccurate information. Some of this misinformation has its basis in good research but is misinterpreted leading to unnecessary expenditures or precautions that only serve to take away precious resources from where they are required.

At times like this we have unprecedented opportunities to show our worth to our clients. Our worth is not only in providing product to our customers. We best serve them by helping them have a good understanding of the problem. Sometimes an increased understanding of a problem leads to not making a sale (this time). However, being the source of education in a time of need helps solidify the trusting relationship between you and your client and leading to future sales and more opportunities.

Since Ebola is spread through contact with fluids and is not airborne, it will not reach air filtration systems (unless the filtration system is in close proximity to the patient and exposed to bodily fluids). Therefore, a sale of a filtration device for Ebola only applications is probably not warranted. However, this is a time when our clients are especially aware of the need for environmental infection control measures. Our clients may be much more willing to spend money on upgrading existing isolation rooms at this time and this may lead to increase opportunities for air filtration sales.

In our Spring 2013 Air Media article entitled “Hospital Filtration–Meeting Your Customers Needs Practically”, we discussed the importance of “learning to provide the appropriate solution that best matches your customers concerns and resources”. In order to be seen as an expert in filtration and as a part of the healthcare facilities environmental infection control team, it is critical that you react to challenges based on knowledge and practicality. If we give into the temptation to react from fear and misinformation we are no longer leading our clients but are merely reacting. Reacting may lead to some short term sales, but if we sell something that is not required or practical we are eventually found out and that leads to a weakened relationship with the customer and a long term reduction in sales and profitability.


Editors Note: For questions or comments on this article, please send an email to:

Hector Valtierra, M.A., M.S., MPH
Southwestern College and Grossmont-Cuyamaca Community College
San Diego, California
Bill Palmer CAFS, CEICC
AeroMed, Inc.



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