The Filovirus Family: The 4 Ebola Viruses

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What is the filovirus family of viruses? What viruses are in the filovirus family?

The filovirus family is a group of viruses that includes the Ebola virus. Filovirus means “thread virus” and refers to the way the virus looks under a microscope.

Keep reading to find out more about the viruses in the Filovirus family.

The Filovirus Family

Ebola belongs to a family of viruses named filoviruses, meaning “thread viruses,” because they look like threads or ropes under a microscope.

There are four viruses in the filovirus family: 

  1. Marburg, the mildest strain, with a kill rate of 1 in 4
  2. Ebola Sudan, with a kill rate of about 1 in 2
  3. Ebola Zaire, the deadliest strain, with a kill rate of 9 in 10 
  4. Ebola Reston, which we’ll discuss in Part 2 

(Shortform note: Since the book’s publication, three more filoviruses have been identified, all of which are strains of Ebola: Bundibugyo, Taï Forest, and Bombali.)

With the exception of Ebola Reston, filoviruses if the filovirus family don’t appear to discriminate between people and animals, and can jump from one to the other. 

Marburg Virus

One virus in the filoviridae family is the Marburg virus. Marburg’s kill rate among patients treated in hospitals is about 1 in 4, which makes Marburg an extremely lethal virus. By comparison, yellow fever’s kill rate is about 1 in 20, and it is considered highly lethal. Filovirus, Ebola, and Marburg are all considered very deadly.

Marburg virus attacks organs, intestines, skin, and connective tissue throughout the body. Its symptoms include: 

  • Extensive bruising
  • Blood clots throughout the body, from organs to extremities
  • Hemorrhages from every orifice
  • Black vomit, a mixture of arterial blood and black specks that indicate hemorrhage
  • Impaired central nervous system
  • Destroyed brain, leading to personality changes, memory loss, and an expressionless face
  • Swollen testicles in male victims
  • Peeling skin on survivors’ faces, hands, feet, and genitals during recovery 

The virus is extremely virulent and highly infective, and it can live in corpses’ eyeballs for months after death. 

(Shortform note: Besides the kill rate, there are no major identifiable differences between Marburg and Ebola. Scientists don’t know why Ebola is deadlier than Marburg.)

Ebola Virus

Ebola virus particles are composed of seven different proteins—each of which scientists know little to nothing about—and a strand of RNA, which contains the virus’s genetic information and instructions for the virus’s replication. Ebola viruses in the filoviridae family are highly infective.

Viruses are parasites. They lie dormant until they can use their sticky surface to latch onto another cell. The cell envelopes the virus, at which point the virus uses the cell’s materials to create copies of itself. The virus continues replicating until the cell either bursts or is exhausted and destroyed. 

Filovirus and Ebola viruses targets the immune system, preventing victims’ bodies from fighting off the disease. However, Ebola’s lethality doesn’t benefit the virus: When a virus’s host dies, it must jump to another host, or else it will also die. The only two “jobs” of a  virus are to survive and replicate. 

Scientists believe Ebola is transmitted through the blood and bodily fluids of infected victims and corpses. But if the virus mutated to become airborne, it would have the potential to snowball into a pandemic—and with a 50-90% kill rate, the effects would be devastating. 

Although Ebola belongs to the filovirus family, it’s distantly related to other diseases, including: 

  • Rabies 
  • Measles
  • Mumps
  • Parainfluenza virus, which causes the common cold in children 
  • Respiratory syncytial virus, which causes potentially fatal pneumonia in AIDS patients

Ebola’s connections to these diseases are evident in certain symptoms, including rashes (like measles) and psychosis (like rabies). 

Ebola Zaire

Ebola Zaireis another virus in the filoviridae family. shares many symptoms with other filoviruses, but Ebola Zaire is the most aggressive of the filoviruses, digesting all the organs and tissues in victims’ bodies until they liquefy into a slime of replicated virus particles. 

This is how Ebola Zaire affects different parts of victims’ bodies: 


  • Blood clots start to clog the bloodstream, getting stuck on the walls of blood vessels and in capillaries, which cuts off blood supply to different areas of the body. 
  • Sections of brain, breast tissue, intestines, kidneys, liver, lungs, skin, and testicles begin to die from lack of blood supply. 
  • All the body’s coagulation factors (proteins that allow blood to clot) are used up internally—causing the excessive blood clots—while the blood that leaves the body can’t clot, simply bleeding incessantly. 
  • Victims bleed from the mouth, including around the teeth and salivary glands. 
  • The eyeballs fill with blood, sometimes causing blood to run from them like tears, and potentially causing blindness. 


  • Hemorrhages under the skin create visible red spots, which quickly spread to become large bruises. 
  • Skin collagen breaks down, causing the layers beneath the skin to liquefy, causing tiny white blisters to appear on the skin. 
  • The skin becomes fragile, easily tearing off and ripping. The surfaces and linings of the tongue, back of the throat, and windpipe also shed.


  • The heart hemorrhages, filling the heart chambers and chest cavity with blood. 
  • The intestines fill with blood, while their lining sheds and is excreted.  
  • Blood clots cause the kidneys to fail, at which point the blood becomes contaminated with urine. 
  • The liver becomes swollen and yellow, then liquefies, and finally dies and rots while the victim is still alive. 
  • The spleen hardens into a massive blood clot. 
  • Many of the organs begin dying and dissolving before the victim is dead. 


  • Dead blood cells clog the brain. Some victims suffer hemispherical strokes, paralyzing one side of the body. 
  • Victims often suffer grand mal seizures, during which their entire body convulses. The seizures cause the blood that is hemorrhaging from every orifice to splatter around the area. Seizures typically happen in the final stages, and the blood splatter gives the virus a chance to jump to a new host before its current host dies. 

After death, the body continues to liquefy, oozing fluids that are packed with virus particles. 

Filoviruses, Ebola, and Marburg are all highly contagious and are still being studied.

The Filovirus Family: The 4 Ebola Viruses

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Like what you just read? Read the rest of the world's best summary of Richard Preston's "The Hot Zone" at Shortform .

Here's what you'll find in our full The Hot Zone summary :

  • The many different strains of Ebola, including the deadliest kind with a kill rate of 90%
  • How scientists unraveled the mystery of a new strain of Ebola
  • How Ebola could become airborne, becoming one of the deadliest viruses known

Carrie Cabral

Carrie has been reading and writing for as long as she can remember, and has always been open to reading anything put in front of her. She wrote her first short story at the age of six, about a lost dog who meets animal friends on his journey home. Surprisingly, it was never picked up by any major publishers, but did spark her passion for books. Carrie worked in book publishing for several years before getting an MFA in Creative Writing. She especially loves literary fiction, historical fiction, and social, cultural, and historical nonfiction that gets into the weeds of daily life.

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