On May 6, 1995, CDC was notified by health authorities and the U.S. Embassy in Zaire of an outbreak of viral hemorrhagic fever in the Kikwit area of Bandundu region, Zaire (1). On May 10, testing of blood specimens from ill patients confirmed that the outbreak was caused by Ebola virus. Through May 24, the investigation of this outbreak by public health authorities has identified a total of 144 persons with viral hemorrhagic fever, including 108 (75%) deaths, in the city of Kikwit and the surrounding area. The median age of ill persons was 37 years (range: 9 months-71 years); 70 were male, 68 were female, and six were of unknown sex. Reported by: M Musong, MD, Minister of Health, Kinshasa; T Muyembe, MD, Univ of Kinshasa; K Mungala, MD, Kikwit General Hospital. Technical Scientific International Coordinating Committee, Kikwit, Zaire. Medecins Sans Frontieres, Belgium. Div of Viral and Rickettsial Diseases, and Div of Quarantine, National Center for Infectious Diseases; International Health Program Office, CDC.
CDC Editorial Note
Editorial Note: From May 17 (when this outbreak was first reported in MMWR {1}) though May 24, the investigation identified an additional 51 cases of suspected Ebola hemorrhagic fever (EHF) in Zaire. The incubation period for EHF ranges from 2 days to 21 days (2); because the outbreak investigation and control measures were initiated on May 10, new cases may represent persons who were exposed to the virus before the institution of the control measures. The ongoing investigation is assessing the effectiveness of these control measures in interrupting transmission, which is believed to result principally from direct contact with ill persons or their blood or body fluids.
Because of the length of the incubation period for EHF, the potential exists for persons with incubating illness to travel from the outbreak-affected area to the United States. To minimize the potential for spread of Ebola virus to the United States, precautionary measures have been instituted, under the provisions of the Foreign Quarantine Regulations, * including 1) issuance of a travel advisory by the U.S. Department of State and an advisory memorandum by CDC distributed to state and local health departments, other federal government agencies, airlines, travel agents, and travel clinics; 2) with the assistance of the U.S. Immigration and Naturalization Service, distribution of the routine Health Alert Notice to all passengers arriving in the United States from Europe and Africa; and 3) distribution of an Ebola Virus Hemorrhagic Fever Alert Notice (EVHFN) to any travelers who have recently been in Zaire -- EVHFN instructs these travelers to contact a health-care provider if they develop a febrile illness during the 3 weeks after they arrive in the United States.
CDC maintains a hotline providing updates on the outbreak of EHF in Zaire (telephone {800} 900-0681).
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Morbidity and Mortality Weekly Report
Centers for Disease Control and Prevention
1600 Clifton Rd, MailStop E-90, Atlanta, GA 30333, U.S.A
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This page last reviewed 5/2/01
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Ebola Zaire
(In all her glory) |
Ebola is a virus named after a river in Zaire, its first site of discovery. A usually fatal filovirus which affects monkeys, apes and humans, it is a cause of viral hemorrhagic fever -- there are others. Filoviruses are string-shaped, often with a little hook or loop at one end. Another, somewhat less deadly filovirus is the Marburg virus.
Ebola is classified as a Level 4 pathogen (higher than AIDS) with a 2 to 21 day (7 to 14 days average) incubation period. There are currently four known strains of Ebola: Zaire, Sudan, Reston and Tai. All cause illness in sub-human primates. Only Ebola Reston does not cause illness in humans. The mortality rate of Ebola victims is between 60% and 90%; with Ebola Sudan at 60% and Ebola Zaire at 90%.
Ebola Zaire attacks every organ and tissue in the human body except skeletal muscle and bone. It is a perfect parasite because it transforms virtually every part of the body into a digested slime of virus particles. The seven mysterious proteins that, assembled together, make up the Ebola-virus particle, work as a relentless machine, a molecular shark, and they consume the body as the virus makes copies of itself. Small blood clots begin to appear in the bloodstream, and the blood thickens and slows, and clots begin to stick to the walls of blood vessels. This is known as pavementing, because the clots fit together in a mosaic. The mosaic thickens and throws more clots, and the clots drift through the blodstream into the small capillaries, where they get stuck. This shuts off the blood supply to various parts of the body, causing dead spots to appear in the brain, liver, kidneys, lungs, intestines, testicles, breast tissue (of men as well as women), and all through the skin. The skin develops red spots, called petechiae, which are hemorrhages under the skin.
Ebola attacks connective tissue with particular ferocity; it multiplies in collagen, the chief constituent protein of the tissue that holds the organs togehter. (The seven Ebola proteins somehow chew up the body's structural proteins.) In this way, collagen in the body turns to mush, and the underlayers of the skin die and liquefy. The skin bubbles up into a sea of tiny white blisters mixed with red spots known as a maculopapular rash. This rash has been likened to tapioca pudding. Spontaneous rips appear in the skin, and hemmoraghic blood pours from the rips. The red spots on the skin grow and spread and merge to become huge, spontaneous bruises, and the skin goes soft and pulpy, and can tear off if it is touched with any kind of ressure.
Your mouth bleeds, and you bleed around your teeth, and you may have hemorrhages from the salivary glands -- literally every opening in the body bleeds, no matter how small. The surface if the toungue turns brilliant red and the sloughs off, and is swallowed or spat out. It is said to be extraordinarily painful to lose the surface of one's tongue. The tongue's skin may be torn off during rushes of the black vomit. The back of the throat and the lining of the wind pipe may also slough off, and the dead tissue slides down the windpipe into the lungs or is coughed up with sputum. Your heart bleeds into itself; the heart muscle softens and has hemorrhages into its chambers, and blood squeezes out of the heart muscle as the heart beats, and it floods the chest cavity. The brain becomes clogged with dead blood cells, a conditions known as sludging of the brain. Ebola attacks the lining of the eyeball, and the eyeballs may fill up with blood: you may go blind. Droplets of blood stand out on the eyelids: you may weep blood. The blood runs from your eyes down your cheeks and refuses to coagulate. You may have a hemispherical stroke, in which one whole side of the body is paralyzed, which is invariably fatal in a case of Ebola. Even while the body's internal organs are becoming plugged with coagulated blood, the blood that streams out of the body cannot clot; it resembles whey being squeezed out of curds. The blood has been stripped of its clotting factors. If you put the runny Ebola blood in a test tube and look at it, you see that the blood is destroyed. Its red cells are broken and dead. The blood looks as if it has been buzzed in an electric blender.
Ebola kills a great deal of tissue while the host is still alive. It triggers a creeping, spotty necrosis that spreads through all the internal organs. The liver bulges up and turns yellow, begins to liquefy, and then it cracks apart. The cracks run across the liver and deep inside it, and the liver completely dies and goes putrid. The kidneys becomes jammed with blood clots and dead cells, and cease functioning. As the kidneys fail, the blood becomes toxic with urine. The spleen turns into a single huge, hard blood clot the size of a baseball. The intestines may fill up completely with blood. The lining of the gut dies and sloughs off into the bowels and is defecated along with large amounts of blood. In men, the testicles bloat up and turns black-and-blue, the semen goes hot with Ebola, and the nipples may bleed. In women, the labia turn blue, livid, and protrusive, and there may be massive vaginal bleeding. The virus is a catastrophe for a pregnant woman: the child is aborted spontaneously and is usually infected with Ebola virus, born with red eyes and a bloody nose.
Ebola destroys the brain more thoroughly than does Marburg, and Ebola victims often go into epileptic convulsions during the final stage. The convulsions are generalized grand mal seizures -- the whole body twitches and shakes, the arms and legs thrash around, and the eyes, sometimes bloody, roll up into the head. The tremors and convulsions of the patient may smear or splatter blood around. Possibly this epileptic splashing of blood is one of Ebola's strategies for success -- it makes the victim go into a flurry of seizures as he dies, spreading blood all over the place, thus giving the virus a chance to jump to a new host -- a kind of transmission through smearing.
Ebola (and Marburg) multiplies so rapidly and powerfully that the body's infected cells become crystal-like blocks of packed virus particles. These crystal are broods of virus getting ready to hatch from the cell. They are known as bricks. The bricks, or crystals, first appear near the center of the cell and then migrate towards the surface. As a crystal reaches a cell wall, it disintegrates into hundres of individual virus particles, and the broodlings push through the cell wall like hair and float away in the bloodstream of the host. The hatched Ebola particles cling to cells everywhere in the body, and get inside them, and continue to multiply. It keeps on multiplying until areas of tissue all through the body are filled with crystalloids, which hatch, and more Ebola particles drift into the bloodstream, and the amplification continues inexorably until a droplet of the hosts blood can contain a hundred million individual particles.
After death, the cadaver suddenly deteriorates: the internal organs, having been dead or partially dead for days, have already begun to dissolve, and a sort of shock-related meltdown occurs. The corpse's connective tissue, skin, and organs, already peppered with dead spots, heated by fever, and damaged by shock, begin to liquefy, and the fluids that leak from the cadaver are saturated with Ebola-virus particles.
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