ASM Ebola FAQ

To help clarify some of the science about the current Ebola virus outbreak, the American Society for Microbiology has gathered a team of experts to answer frequently answered questions. If you have a question you would like to see answered here, please send it to ebola@asm.org. For additional information about the Ebola virus outbreak from ASM and other organizations, please visit our Ebola Resources page.

How can a person get infected with Ebola virus?

Based on the study of previous outbreaks of Ebolaviruses, it is known that the virus spreads from person to person by direct contact with blood, body fluids, or skin of infected individuals. In the laboratory, animals may be infected with Ebola airborne virus particles, but this mode of transmission has never been observed among humans (http://www.cdc.gov/vhf/ebola/transmission/human-transmission.html).

Recently an epidemiologist suggested that Ebola virus could mutate and become transmitted by the airborne route. When it comes to viruses, it is always difficult to predict what they can or cannot become airborne. It is instructive, however, to see what viruses have done in the past, and use that information to guide our thinking. Therefore we can ask: has any human virus ever changed its mode of transmission? The answer is no. We have been studying viruses for over 100 years, and we’ve never seen a human virus change the way it is transmitted. There is no reason to believe that Ebola virus is any different from any of the viruses that infect humans and have not changed the way that they are spread (http://www.virology.ws/2014/09/18/what-we-are-not-afraid-to-say-about-ebola-virus/)

Ebola virus infection can also be transmitted if an infected person coughs or vomits at close range. In this case large droplets landing on the mucous membranes can initiate infection. Although these droplets are traveling through the air, this mode of transmission is considered a form of contact transmission, not airborne transmission (http://www.virology.ws/2014/09/27/transmission-of-ebola-virus/)

But I heard that Ebola virus can be transmitted in the air from pigs to monkeys. Doesn’t that mean the virus could be transmitted this way among humans?

In a porcine transmission experiment (http://www.ncbi.nlm.nih.gov/pubmed/23155478), animals were infected by dripping virus into the nose, eyes and mouth, and placed in a room with cynomolgous macaques. The pigs were allowed to roam the floor, while the macaques were housed in cages. All of the macaques became infected. However it is not known how the virus was transmitted from pigs to macaques, because the design of the experiment did not make it possible to distinguish whether the transmission was by aerosol, small or large droplets in the air, or droplets created during floor cleaning which landed inside the cages. The authors also say that transmission between macaques in similar housing conditions was never observed.

How stable are Ebola virus particles? Can I get infected by touching a contaminated object?

Ebola virus infectivity is quite stable at room temperature (20°C), especially in the dark, where it can remain for several days. Infectivity is largely inactivated in 30 minutes at 60°C. Infectivity is greatly reduced or destroyed by high doses of ultraviolet light and gamma irradiation, lipid solvents, beta-propiolactone, the photo-inducing alkylating probe 1,5-iodonaphthylazide, guanidiuium isothiocynates, and commercial hypochlorite and phenolic disinfectants (Feldman et al, 2013 32:923, Fields Virology; Lytle & Sagripanti J Virol 79:14244 2014; Sagripanti et al Arch Virol 155:2035, 2010; Sagripanti & Lytle Arch Virol 156:489, 2011; Piercy et al, J Appl Micro 109:1531, 2010).

If an infected person contaminates an environmental surface with body fluids, it might be possible to acquire infection by touching these surfaces and transferring virus to mucous membranes. This type of transmission is more likely to occur in health care settings where ill patients are shedding large amounts of virus particles. However, transmission of the virus from inanimate objects has rarely been observed in previous outbreaks (http://www.cdc.gov/vhf/ebola/transmission/human-transmission.html, http://www.ncbi.nlm.nih.gov/pubmed/17940942)

I’ve heard that Ebola virus is mutating. What does this mean?

Mutations are a way of life for an RNA virus and mutations come and go every time a genome replicates – it is likely that every single genome copy of an RNA virus has a mutation (http://www.virology.ws/2009/05/10/the-error-prone-ways-of-rna-synthesis/). The key is to determine whether these changes affect any of the biological properties of the virus, such as transmission, stability, or virulence.

A recent study determined the genome sequences of 99 Ebola virus isolates from 78 patients in the Sierra Leone outbreak (http://www.ncbi.nlm.nih.gov/pubmed/25214632). This work shows that the viruses are very similar to isolates from recent outbreaks in Central Africa, and a small number of genetic changes were observed. Whether these changes have any effect on the properties of the virus is not known.

Why has the quarantine period for someone infected with Ebola virus set at 21 days?

The quarantine period for an infectious disease is the time that a potentially infected individual should be kept away from others to prevent transmission of infection (http://www.virology.ws/2014/10/16/the-quarantine-period-for-ebola-virus/). The length of the quarantine period is based on the incubation period, the time before symptoms of an infection appear. For Ebola virus, the incubation period is 2-21 days after infection. During this time it is believed that individuals infected with the virus are not contagious, but they do have low levels of virus in the blood (http://www.ncbi.nlm.nih.gov/pubmed/15047846). For Ebola virus, patients are not thought to be contagious during the incubation period. They are only thought to be contagious once they show signs of infection (fever, etc).

The length of the quarantine period of Ebola virus infection is based on the incubation period observed during previous outbreaks. The incubation period for the first 9 months of the current West African outbreak is similar to those determined from previous outbreaks (http://www.virology.ws/2014/10/16/the-quarantine-period-for-ebola-virus/).

Are there any treatments for Ebola virus infection?

Chances of survival significantly improve when Ebola virus infection is detected early, and patients are given intravenous fluids, maintaining balanced electrolytes, oxygen status, and blood pressure (http://www.cdc.gov/vhf/ebola/treatment/index.html)

Several Ebola virus vaccines and antiviral drugs are being tested for safety in humans, but none have yet been approved by the Food and Drug Administration.


The members of ASM’s Ebola virus FAQ Response team are:

Vincent Racaniello, Columbia University
Lynn Enquist, Princeton University
Ron Atlas, University of Louisville
John Connor, Boston University School of Medicine
Andrea Marzi, National Institutes of Health
Elke Muhlberger, Boston University School of Medicine
Sean Whelan, Harvard Medical School

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