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Ebola Virus

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Published: September 2014

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As of August 22nd , there have been over 2600 suspected or confirmed cases of Ebola hemorrhagic fever and over 1400 deaths attributed to this virus. Ebola hemorrhagic fever is caused by infection with Ebola virus and is a severe, often fatal disease in humans and nonhuman primates. Ebola virus is not spread through airborne routes and individuals are not infected through ingestion of the virus. Human-to-human transmission occurs by either direct or close contact with body fluids from an infected individual or through blood-borne means, for example through direct inoculation with a contaminated needle. Therefore, it is critical that providers contact their local state health laboratories and/or the CDC for guidance on specimen collection, handling and transport.

Presenter: Elitza Theel, PhD

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Thank you for the introduction and to the viewers for joining us today. For this Hot Topic, I will briefly review some background on Ebola virus, the current outbreak, and clinical aspects of infection. Before we begin, I should note that I have nothing to disclose.

Presentation Outline

During this presentation I will provide an overview of Ebola virus and discuss how it is transmitted. I will also review the epidemiology of the virus and provide a status update on the ongoing outbreak in West Africa. I’ll then discuss the clinical manifestations of disease, diagnosis, treatment, and finally prevention.

Ebola Virus

Ebola virus is a single-stranded RNA virus and is actually a subspecies of the overarching Ebolavirus genus. Ebolaviruses, along with Marburg virus are the 2 members of the Filoviridae family of viruses, all of which are associated with causing severe hemorrhagic fever in humans. Within the Ebolavirus genus are 5 subspecies, including Ebola virus, the causative agent of the current outbreak, Sudan virus, Tai Forest virus, Bundibugyo virus, and Reston virus, which primarily causes disease in nonhuman primates.

Ebola virus was first identified in 1976 from 2 independent outbreaks of hemorrhagic fever in what is now the Democratic Republic of Congo and southern Sudan. It is thought that the index patient was traveling along the Ebola River in the Democratic Republic of Congo when the exposure and infection occurred. Since the late 1970s, outbreaks of Ebola virus have been largely sporadic and have all been restricted to the African continent.

Transmission

Regarding transmission of Ebola virus, the natural environmental reservoir for the virus is unconfirmed, though scientists do believe that Ebola virus is a zoonotic agent and is maintained in the animal host, most likely fruit bats. The means by which it is transmitted from the animal host to the human host however, remains unclear. Human-to-human transmission occurs by 2 primary routes, either direct or close contact with body fluids from an infected individual or through bloodborne means, for example through direct inoculation with a contaminated needle.

It is perhaps equally important to understand by what routes the virus is not spread. Ebola virus is not considered a respiratory virus and is therefore not spread through airborne routes and individuals are not infected through ingestion of the virus from either water or food.

Ongoing Ebola Outbreak in West Africa

As many of you are aware, the current Ebola virus outbreak in West Africa has affected 4 countries, including Guinea, Sierra Leone, Liberia, and most recently Nigeria. As of August 22th, there have been over 2600 suspected or confirmed cases of Ebola hemorrhagic fever and over 1400  deaths attributed to the virus. Notably, this is the largest documented Ebola virus outbreak in Africa and the first one reported in West Africa. Importantly, there has not been transmission of the virus in the United States and due to heightened public awareness and our sophisticated health care system, the risk of this occurring remains low.

Clinical Presentation

Following infection, the incubation period for Ebola virus can range from 2 to 21 days, though the average is from 8 to 10 days prior to onset of symptoms. Ebola virus and members of the Filoviridae family of viruses cause hemorrhagic fever in humans and patients typically present with sudden onset nonspecific symptoms, including fever, malaise, myalgia, nausea and vomiting, and headache.

The majority of individuals will subsequently develop hemorrhagic symptoms and multi-organ dysfunction. While some individuals are able to recover, most unfortunately are not. The reasons behind this are not entirely understood, though it is assumed that patients who recover are able to develop a strong immune response to the virus earlier on as compared to those who succumb to infection. In general, depending on the species and strain, the fatality rate of Ebola viruses can range from 40% to 90%. The fatality rate for the current outbreak has ranged from 50% to 60% of infected individuals.

Diagnosis

With regards to the diagnosis of an Ebola virus infection, it is critical that providers contact their local state health laboratories and/or the CDC for guidance on specimen collection, handling, and transport.

We ask that clients do not submit clinical specimens from patients who are being evaluated for Ebola virus infection to Mayo Medical Laboratories for any testing. Mayo Medical Laboratories does not offer any assays for detection of Ebola virus and in an effort to minimize any potential exposure to laboratory personnel we ask that clients please refer to the CDC website indicated below for the most up-to-date information regarding specimen collection and testing.

Treatment

Unfortunately, there is no directed antiviral treatment against Ebola virus infection. It is important however to exclude other potential causes of severe disease which are endemic to West Africa, including malaria. In general, treatment is largely supportive, including maintaining electrolyte and fluid balance, oxygen levels, and blood pressure.

Prevention

With regards to prevention, there is no currently available vaccine. However, the risk of an outbreak in the United States remains low and this can be kept at a low level if individuals continue to adhere to the recently released CDC travel restrictions to areas affected by the ongoing outbreak in West Africa.

Summary

In summary, as many of us are aware, the Ebola virus outbreak remains an ongoing problem in West Africa and human-to-human transmission occurs through direct contact with body fluids from infected individuals. Symptoms of infection are largely nonspecific early on, and many patients often develop severe hemorrhagic disease which has a high fatality rate. Regarding diagnosis of Ebola virus infection, it is important to contact your state health laboratories and the CDC for the most up-to-date recommendations and to refrain from sending samples from suspected cases of Ebola virus to Mayo Medical Laboratories. Finally, care of patients with Ebola virus is largely supportive, though new treatments are being evaluated during the current outbreak with promising results.


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