Masood N. Khan M.D., F.A.C.P
Ebola virus belongs to the family of ‘filoviridae’ which are shaped like a thread. It is named after a river in Sudan. It is the second virus discovered in the class of thread viruses. The other one is called Marburg virus. It is 80 nanometer in diameter and as long as 14000 nanometer, the average being 700 nanometer.
The natural reservoir for Ebola is unknown. Epidemiologists have tested bats, monkeys, spiders and ticks for the virus, but have not been able to acquire definitive data. Common factors indicate that the natural reservoir is part of rural Africa, and CDC tests have shown that 10% of all Asian and African monkeys have antibodies to filoviruses meaning they have been infected with the virus and survived.
The incubation period which means the time interval between the exposure, contact or entry of virus in the body and the onset of first symptom, is 3-21 days. The average incubation period in the hospital setting, specifically the needle-transmission is 5-7 days and the average incubation period for close-contact transmission is 6-12 days.
Unlike respiratory illnesses like measles or chickenpox, which can be transmitted by virus particles that remain suspended in the air after an infected person coughs or sneezes, Ebola is transmitted by direct contact with body fluids of a person who has symptoms of Ebola disease. Although coughing and sneezing are not common symptoms of Ebola, if a symptomatic patient with Ebola coughs or sneezes on someone, and saliva or mucus come into contact with that person’s eyes, nose or mouth, these fluids may transmit the disease.
Sudden onset of fever and malaise with extreme prostration and weight loss is the presenting picture. Subsequent symptoms include sore throat, chest pain, abdominal pain, skin rash, and diarrhea. The disease becomes life-threatening because blood fails to clot, and patient may begin to bleed not only from needle/ injection sites but spontaneously into the skin, stomach, intestines, and other internal organs. This situation leads to fluid from the blood, accumulating in the internal organs causing swelling. Fluid in the lungs gives rise to severe shortness of breath. If patient is lucky to overcome the infection, within 7 to 10 days will begin to recover. Recovery can take 5 weeks or more, and is accompanied by prostration, weight loss, and sometimes temporary loss of memory.
Patients who are at greatest risk of dying experience extensive hemorrhage into the skin, mucous membranes, and internal organs, including the cavities of the stomach, intestines and lungs. Swelling of the spleen, lymph nodes, kidneys, and brain occurs. By the end of the first week of acute symptoms, the patient can bleed freely from the eyes, ears, and nose and may begin to vomit black sludge of blood. Capillary leakage results in vascular collapse. Coma, convulsions and respiratory distress lead finally to death.
Infected persons will develop antibodies and the diagnosis is made by detecting these antibodies in the blood. There are two types of antibodies that differentiate between acute active infection and old healed infection. Electron microscopy is useful in diagnosing filovirus infection, but does not help distinguish Ebola from the morphologically identical Marburg virus.
The reason infection from Ebola is different from other viral infections is because it makes immune system of the body which defends the infection, inactive. So even though antibodies are produced, they cannot kill the virus because the virus blocks the specific proteins that keep the antibodies active and functioning. Basically Ebola paralyses the natural defense system of the body that is needed to overcome the infection. The death rate is 50% but could reach as high as 70% if health care system is deficient and poor. That means out of 100 people who are infected 50 to 70 will die. So far there is no specific treatment for Ebola. For preventive purposes, the virus itself is sensitive to lipid solvents, detergents, commercial hypochlorite disinfectants, and phenol disinfectants. The virus can also be destroyed in the environment by ultraviolet and gamma radiation.
Intense research is going on to find cure on three levels.