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Health News of Tuesday, 26 August 2014

Source: leffortcamerounais.com

How Ebola virus spread - Dr. Oliver Verbe Birnso

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Ebola virus shares a common toxic glycoprotein with some other viruses like the Indiana virus. This means a person previously infected with either virus becomes immune, at least partially, from subsequent Ebola or Indiana virus infection( having had an infection provides a better form of protection or 'vaccination').

Even a small contact with contaminated body fluid (blood, saliva, semen, vaginal fluid), is able to result in an infection--viruses are tiny particles that easily penetrate tissues. It takes a couple of weeks for an infected person to develop signs and symptoms. This is incubation period, during which viral proteins are being made, preparing the virus for subsequent multiplication and in anticipation of spread throughout the body. At this point in time, the person's fluid is highly contaminating and infecting, due to the high viral titre or load present therein.

In the body, the Ebola virus particularly infects the white blood cell type called the monocyte, in which it divides and produces viral particles that break open the monocyte, taking, along with them, snippets of the membrane that they wrap round themselves, on exit. Then, they move on to infect the liver cells and the cells of the blood vessel linings. This way, the Ebola virus affects practically all organs in different parts of the body, that is, every nook where blood vessels are to be found.

It is possible, at this point, for a much healthier and more robust monocyte to thwart the infection, by engulfing and digesting the virus, instead; a past healthy lifestyle and good nutrition helping.

When the virus infects and eventually damages the monocytes, these immune cells begin to give distress signals, meant to alert, and destined to, other immune cell counterparts. By secreting toxins called cytokines (TNF, IL 6&8), used to ask for help, from other immune cells, monocytes are in effect calling out on these cells to join in the fight to stem the virus.

At the same time, in a counterattack mode, the virus secretes a glycoprotein to enable it bind to our blood vessel cells, preventing these from binding to each other and making blood vessels leaky. This viral glycoprotein also binds to and disables another body defense cell type called the neutrophil, preventing it from responding to the s.o.s., as per the request sent by the monocyte. The body now becomes defenseless, in the face of the attack. The first line of defense, normally jointly put up by the monocyte and the neutrophil, is now completely put out of action.

The signs and symptoms of Ebola can be clearly derived from the above pathophysiological presentation:

The TNF, secreted by monocytes, goes to the brain, activates the different centres involved, and brings about the rise in temperature (fever), vomiting and lack of appetite. It also causes the severe pain that is characteristic of Ebola

If fever were to be high enough, it would kill the virus. In many infections, people with the genetic or epigenetic predispositions to having high fevers tend to fare better, in terms of survival rates . Although the fever may appear scary, at first sight, as it tends to cause convulsion, it may well turn out to be a good thing for a disease like Ebola which presently has no cure.

TNF and IL6 and 8 from monocytes, and the toxic glycprotein from the virus, cause damage to the cell- to - cell junction contacts and this renders blood vessels leaky, resulting in hemorrhage or bleeding, in practically every organ in any part of the body. The name hemorrhagic fever derives from this manifestation.

The loss in the integrity of the cell-to-cell contacts in blood vessels and in the liver, and the accompanying blood/ fluid loss, result in shock--the inability of sufficient quantity of blood to perfuse and supply tissues.

Damage to the liver leads to the release of clotting factors into the blood stream and this leads to heightened clotting. A heart attack or stroke can occur. A clot may lodge in the lung, giving rise to the deadly pulmonary embolism that results in respiratory failure.

The hemorrhage, shock and clotting will lead to kidney failure.

The disease therefore causes multi-organ failure. This accounts for the rapid morbidity and high mortality, we see in Ebola, of up to 90 percent, making it one of the most deadliest infections, we know, to date .

Treatment is non-specific and supportive, and aims at replacing electrolytes lost and restoring blood volume to alleviate shock and ameliorate physiological function; and providing oxygen /respiratory support for functionality.

After a patient makes clinical recovery, the virus continues to be shed in semen for weeks and transmission is still possible

Prevention involves avoiding getting into direct contact with fluid from an infected person. Transmission is unlikely before signs and symptoms emerge because the virus has not yet divided and spread throughout the body, to be in sufficient quantities in body fluids. Saliva droplets and formites may spread Ebola but there is practicaly no indication as to infectivity by these means. The amount of contaminated fluid one gets in contact with and the frequency of exposure to it, all seem to be critical in transmission. The integrity of the skin and the innate immune system seem to play a big role here until compromised or overwhelmed.

Fruit bats are the main reservoir in the wild though macaque monkeys and pigs are known hosts and vectors. Other animal species may also act as vectors. Fruit bats carry the virus but do not readily fall ill and die of it, due to the evolutionary long time contact they have had with it, and that has conferred some partial immunity and tolerance on them.

Patients should be isolated and caregivers or suspected contacts quarantined and monitored to prevent spread. They should be released only after the incubation time has elapsed.

Healthcare personnel and caregivers should wear doubly protective garments. Gloves should be doubled and the surgical cap and protective gorgles donned when attending to the patient.

Cremation of the corpse should be prohibited. Remains of the patient and medical waste should preferably be incinerated. Everyone in charge of these should wear the necessary protective gears.

A battery of tests is necessary to prove or refute an infection. Tests look for antibodies and viral RNA particles in the sample. They must be confirmed within 48 hours. There are hemorrhagic fevers other than Ebola and tests will rule them out. Because the signs and symptoms may be non-specific early on in the infection, there is no way one can tell Ebola from, say, malaria.

Candidate vaccines are still on trial and are showing good results in other primates. Drugs are at a developmental stage and because of the emergency situation currently in West Africa, the FDA has only just permitted tests on human victims of Ebola. These are still experimental as are candidate vaccines. Personal hygiene, as with practically all infections, is the best bet, for now. Quarantine of suspected carriers and isolation of patients are other measures to take.

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