Public Health

Zaire Ebolavirus (EBVOV)

Zaire Ebolavirus is the most common species of ebolavirus, and is often referred to simply as Ebola Virus (EBOV). It was fist discovered in what was formerly Zaire, now the  Democratic Republic of the Congo (DRC), in 1976. At first it was suspected to be a new strain of Marburg Virus, but was renamed "Ebola Virus" in 2010. It is responsible for the largest number of outbreaks, including the 2013-2016 Western Africa Ebola Virus Epidemic.

It is the most virulent strain of ebolavirus, accounting for approximately 1,400 human cases in 13 outbreaks over 35 years, with a case fatality rate <90%. The natural reservoir is believed to be fruit bats, and it can also be transmitted human-to-human and from other animals to humans through bodily fluids

Sudan Ebolavirus (SUDV)

The Sudan Ebolavirus was discovered in Sudan in 1977. It was introduced as Sudan Ebola Virus in 1998. Today, it is commonly referred to as "Sudan Virus" (SUDV).  It is clinically indistinguishable from the Zaire strain of Ebolavirus, however it is much less transmissible. The first outbreak of Sudan Virus was in South Sudan 1976, infecting 284 people and killing 151. There had been three other previous outbreaks of SUDV prior to the current outbreak in Uganda in September 2022.

The Sudan Virus is notable in that unlike the more common [Zaire] Ebola Virus, there is no vaccine available to prevent disease.

Bundibugyo ebolavirus (BDBV)

BDBV first appeared in 2007 in a viral hemorrhagic fever outbreak in the Bundibugyo District in Western Uganda. In this outbreak there were 149 confirmed human cases and 37 deaths (a case fatality rate of 35%). Bundibugyo virusvirus was first designated in 2008.

In August 2012 a second outbreak of Bundibugyo virus was reported by the the World Health Organization. It initially infected 15 and killed 10 (including 3 HCW) in the Orientale Province in the Democratic Republic of the Congo (DRC). By November 2012 the DRC announced that the final outbreak count was 77 human cases (36 confirmed, 17 probable, and 24 suspected) with 36 deaths (case fatality rate of 47%).

Taï Forest ebolavirus (TAFV)

Formally known as Côte d’Ivoire ebolavirus (CIEBOV), it was first introduced as new strain of Ebolavirus in 1995. There has only been a single known human infection of TAFV, a scientist performing necropsies on infected Western Chimpanzees during a viral hemorrhagic fever outbreak in 1994. Her disease course was similar to Dengue Fever and she had a full recovery within six weeks of infection.

Symptoms may appear anywhere from 2 to 21 days after contact with the virus, with an average of 8 to 10 days. The course of the illness typically progresses from “dry” symptoms initially (such as fever, aches and pains, and fatigue), and then progresses to “wet” symptoms (such as diarrhea and vomiting) as the person becomes sicker.

Primary signs and symptoms of Ebola often include some or several of the following:

• Fever
• Aches and pains, such as severe headache and muscle and joint pain
• Weakness and fatigue
• Sore throat
• Loss of appetite
• Gastrointestinal symptoms including abdominal pain, diarrhea, and vomiting
• Unexplained hemorrhaging, bleeding or bruising

Other symptoms may include red eyes, skin rash, and hiccups (late-stage).

Ebola is a zoonotic virus and cientists think people are initially infected with Ebola virus through contact with an infected animal, such as a fruit bat or nonhuman primate. From there it can quickly spread from person-to-person.

The virus spreads through direct contact (such as through broken skin or mucous membranes in the eyes, nose, or mouth) with:

• Blood or body fluids (urine, saliva, sweat, feces, vomit, breast milk, amniotic fluid, and semen) of a person who is sick with or has died from Ebola virus disease (EVD).
• Objects (such as clothes, bedding, needles, and medical equipment) contaminated with body fluids from a person who is sick with or has died from EVD.
• Infected fruit bats or nonhuman primates (such as apes and monkeys).
• Semen from a man who recovered from EVD (through oral, vaginal, or anal sex). The virus can remain in certain body fluids (including semen) of a patient who has recovered from EVD, even if they no longer have symptoms of severe illness. There is no evidence that Ebola can be spread through sex or other contact with vaginal fluids from a woman who has had Ebola.

Marburg virus was first recognized in 1967, when outbreaks of hemorrhagic fever occurred simultaneously in laboratories in Marburg and Frankfurt, Germany and in Belgrade, Yugoslavia (now Serbia). Thirty-one people became ill, initially laboratory workers followed by several medical personnel and family members who had cared for them. Seven deaths were reported. The first people infected had been exposed to Ugandan imported African green monkeys or their tissues while conducting research.

Marburg Virus Host

The reservoir host of Marburg virus is the African fruit bat, Rousettus aegyptiacus. This African fruit bat is a sighted, cave-dwelling bat that is found widely across Africa. Given the fruit bat’s broad geographic spread, more areas are potentially at risk for outbreaks of MVD than previously suspected. The virus is not known to be native to other continents, such as North America.

Fruit bats infected with Marburg virus do not show obvious signs of illness. Primates (including people) can become infected with Marburg virus, which can cause serious illness or death. Further study is needed to determine if other species may also host the virus.

Spillover to Humans

It is unknown how Marburg virus first spreads from its animal host to people; however, for the 2 cases in tourists visiting Uganda in 2008, unprotected contact with infected bat feces or aerosols are the most likely routes of infection.

Human-to-Human Transmission

After this initial crossover of virus from host animal to people, transmission occurs through person-to-person contact. The virus spreads through contact (such as through broken skin or mucous membranes in the eyes, nose, or mouth) with:

• Blood or body fluids (urine, saliva, sweat, feces, vomit, breast milk, amniotic fluid, and semen) of a person who is sick with or died from Marburg virus disease
• Objects contaminated with body fluids from a person who is sick with or has died from Marburg virus disease (such as clothes, bedding, needles, and medical equipment)
• Semen from a man who recovered from MVD (through oral, vaginal, or anal sex)*

*Data on Marburg virus is limited; however, it is known to persist in the testicles and inside of the eye, similar to ebolaviruses. Since Marburg virus and ebolaviruses are both in the same virus family (Filoviridae) it can be assumed that persistence of the Marburg virus in other immune privileged sites (placenta, central nervous system) may be similar. There is no evidence that Marburg virus can spread through sex or other contact with vaginal fluids from a woman who has had MVD.

There is no specific treatment for Marburg virus disease. Supportive hospital therapy should be utilized, which includes balancing the patient’s fluids and electrolytes, maintaining oxygen status and blood pressure, replacing lost blood and clotting factors, and treatment for any complicating infections.

Known Cases and Outbreaks of Marburg virus disease, in Chronological Order