The Ebola Virus
The Ebola virus is one of the most deadly viruses that man kind has ever seen.
In clinical cases it has a mortality rate of 50%-90%. The Viruses has many different strains including Marburg, Ebola Zaire, Reston and Sudan, each named after the location of their first clinical case. They each cause different symptoms and different mortality rates. Non the less, the collection of Ebola viruses at the present, pose a serious health threat to people in undeveloped countries and potentially in developed ones as well.
The first documented clinical case of the Ebola virus was in 1967. Marburg, a strain of the virus was seen in laboratory workers in Marburg, Germany. The workers had been exposed to tissue and blood from African green monkeys imported from Uganda. They were to be used as tests subjects. 25 of the workers were exposed to the virus, 7 died. The same virus had confirmed cases in Uganda at approximately the same time. Sporadic instances of the Marburg strain have been reported in several other African countries since then. The first major outbreak of the ebola virus was in 1976, in Zaire and in Sudan. "Over 500 cases were reported, with mortality rates of 88% in Zaire and 53% in Sudan"1 The cause of these outbreaks still remain unknown. No association with monkeys could be attributed to either of the outbreaks. The only other case besides in Marburg that Ebola seemed to be associated with monkeys was a filovirus (family of viruses containing Ebola) isolated from cynomolgus monkeys from the Philippines. This Virus caused no serious symptoms in humans. Scattered outbreaks of Ebola have been reported in Central Africa for several years.
The Ebola virus is a member a family of RNA viruses known as filoviruses. Ebola is a negative stranded RNA virus. The virus partial has the shape of a long stand with loops on the end, like worms. There are variations on this shape, depending on the specific virus. Each virus in the filovirus family contain a nucleocapsid consisting of a dark central space surrounded by a helical capsid, the outer protein coat of a cell. A channel exists in the nucleocapsid. This is where the Nucleic acid (DNA) is stored. "The viral partical is surrounded by a lipoprotein unit membrane envelope derived from the host cell plasma membrane. Spikes of approximately 7nm, spaced at approx 10nm intervals are visible on the viron surface."- Properties of Viron, Excerpt from virology Cd.
Once the Virus partical enters the cell it uses the host cells DNA as material to construct replica ebola virus particals. This is known as a lytic cycle. The new particals form "inclution bodies": small sites where the individual particals grow. As the inclusion bodies grow and become more structured, the cell bursts and the viruses quickly find new cells to infect. This process is extremely rapid. Ebola is known for it's short incubation period of 2 to 21 days.
The method of primary infection with the ebola virus in a natural is still unknown,
however secondary transmission occurs through sexual contact and infected blood samples. Transmission usually occurs between an infected patient and hospital workers or family members that care for the patient. The virus has also been transmitted by reusing hypodermic needles in hospitals where supplies are limited.There is also evidence of respiratory spread of infection. There was a documented case with the Reston virus where the virus was spread by droplets of vomit infecting people. This doesn't mean that the virus is air born it means that direct contact with contaminated blood can cause infection. "Other area's the virus has been found in is in throat washes, urine, soft tissue effusates, semen and anterior eye fluid. It has also been regularly isolated from autoptic material, such as spleen, lymph nodes, liver and kidney but rarely from brain or other nervous tissues"- [ Properties of Viron, Excerpt from virology Cd.}
The symptoms of Ebola develop 4 to 16 days after initial infection. "Persons develop fever, chills, headaches, muscle aches, and loss of appetite. As the disease progresses, vomiting, diarrhoea, abdominal pain, sore throat, and chest pain can occur. The blood fails to clot and patients may bleed from injection sites as well as into the gastrointestinal tract, skin, and internal organs. "- [CDC, http://www.cdc.gov/] The Ebola and Marburg virus causes sever hemorhagic fever in humans . Between 5 and 7 days sever haemorrhages form on every orifice of the body. Between 7 and 16 days, death occurs either from shock or loss of blood. The Reston virus causes hemorhagic fever in monkeys but has no serious effects on humans. The most virulent strand of Ebola is the Ebola Zaire virus. This strand of Ebola has the highest mortality rate of the filoviruses.
At this time there is no cure for the Ebola virus. With the use of new technology such as recombinant DNA research, we are now able to see and begin to understand the molecular structure of Ebola and it's mutations. Virologist are hopeful that the details of virus replication and virus-host interactions will be uncovered in the near future. By using less virulent filoviruses such as reston virus, virologists can see how Ebola works in a slower less destructive form. New tools and new ideas will also contribute to the advancement of a cure for Ebola.
Ebola and its closely related viruses are causing deaths all over undeveloped countries. E bola has one of the highest mortality rates of all viruses. New research and new ideas will contribute to a cure. Scientists are hopeful that further outbreaks of Ebola such as Zaire and Sudan can be avoided As long as simple safety precautions are taken. Hopefully Ebola will soon take it's place among the defeated viruses of the world.
Centers for Disease Control, Ebola research and statistics.
Marburg and Ebola viruses, Excerpt from the Encyclopedia of Virology CD-ROM
World Health Orginization, Emerging and Other Communicable Diseases (EMC)