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Ebola questions

Ebola virus

Could Ebola Become an Airborne Virus?

The experience over many years with Ebola clearly indicates that it is not airborne. We need to look at science and evidence-based facts. Ebola is an RNA virus. It replicates, and RNA viruses can mutate. However, most of those mutations are not associated with a relevant, functional change. If you look historically at viruses, it is virtually unheard of (and there are no previous examples of) a virus mutating and completely changing its mode of transmissibility. Ebola is not airborne now, and although it is not impossible for it to become airborne, it would be an extraordinarily unlikely event for that to happen.

Can Ebola Be Transmitted Through a Sneeze?

The only time that Ebola is in the lungs in sufficient quantities to produce virus in fluid which could be expelled during a sneeze is during extraordinarily advanced disease. A typical Ebola patient doesn’t have a lot of virus in the lungs, but a person with advanced disease who is close to death could have a lot of virus in the lungs. During intubation or when a very sick infected person coughs or sneezes, then an improperly protected healthcare worker could be at risk of being infected. It would be a stretch to say that someone who is infected but well enough to walk around among other people would have enough Ebola in his or her lungs to be able to spread it by sneezing. There should be care not to create a hypothetical scenario that is so unrealistic that it almost never could happen. Focus on the fact that Ebola is transmitted through direct contact with bodily fluids (mucus, blood, vomit, or diarrhoea) of a person who is sick. That is why healthcare workers are most at risk, particularly if they don’t have the proper personal protective equipment (PPE).

A person who is infected at a very early stage, when there are no symptoms, does not transmit virus. We know that from many years of experience. Although I can understand the hypothetical question about Ebola becoming airborne, in reality, it is a scenario that wouldn’t occur.

When Will a Vaccine Be Ready and How Will It Be Distributed?

It cannot be predicted when a vaccine will be ready because vaccines are still experimental. There has been considerable progress with Ebola vaccines. There have been vaccine candidates which have been shown to be quite effective in animal models but experience tells us that sometimes when something works in an animal model when we test it in humans it can be either unsafe or not effective.

There are phase 1 trials with two vaccines to determine whether they are safe, whether they are associated with any adverse events, and whether they can induce the kind of response that would predict that the vaccine would be protective. We should know the answers to these questions by November because the trials started in September and in early October. By November we will know more and at that point the trials will expand into thousands of people in the West African setting to determine whether the vaccines actually work and to ensure that they don’t result in paradoxical harmful effects.

If everything goes as we hope (there is never a guarantee), we could conceivably know by several months into 2015 whether these vaccines work. If they do, we would ratchet up production to make them widely distributed and available to the people of West Africa.

Can a Blood Test Detect Ebola Before Symptoms Appear?

It is very unlikely that a blood test [for Ebola] will be positive if there are no symptoms. More than 90% of people have fever as one of their first symptoms. The Ebola polymerase chain reaction (PCR) is a molecular test. It does not culture the virus; it determines the molecular component of the virus. The PCR test becomes positive right around the time when the symptoms begin. The issue is that if a person does not have any symptoms, it is likely that the virus titte is so low that the PCR test might not even pick it up, and the virus would not be in sufficient quantities to be able to be transmitted. The test is almost always positive right at the time that symptoms are starting.

There is work ongoing on much more sensitive rapid tests, and whether those will increase the ability to detect Ebola earlier, we can’t say right now. We know that PCR is a good test at the time a person develops symptoms.

How Do We Know Whether Treatments Really Work?

Right now all treatments are in the experimental stage. These treatments are not being used in the context of clinical trials, which means that we have nothing with which to compare them. When you give a treatment, it is wrong to assume that the person got better because of the experimental drug or treatment that was given. The history of medicine tells us that this is a dangerous assumption.

Unlike drugs that have been proven to be safe and effective, Ebola treatments are experimental, so it’s conceivable that not only might they not work, they might actually be too toxic to use. And because a patient is so sick with Ebola, we might not be able to distinguish the toxic effect of the drug from the very deleterious effects of the virus on the body. We need to do clinical trials and balance making experimental drugs available to people who might need them, with determining whether they actually work.

Could Serum Be Made From Ebola Survivors’ Antibodies to Help Those Affected?

There are already examples of Ebola treatments, such as the passive transfer of plasma. This involves taking the plasma from a convalescent Ebola patient who is feeling well and has no detectable virus, and transferring that plasma to a patient with Ebola infection to try to help the infected person suppress the virus. Dr Kent Brantly, who was transferred from West Africa the US, has donated multiple units to several individuals. It is certainly possible that passive transfer of plasma is an effective modality of treatment, but we don’t know whether it works. NIH and others are already working on protocols to determine whether the passive transfer of plasma has a true beneficial effect.

Is Ebola Curable?

The human body’s immune system is capable of ridding the body of virus, clearing it, and allowing a person to recover. It is important to distinguish recovery from cure. Cure implies that you give an agent to block the virus. You can recover with your own natural immune system’s ability to clear the virus. We know that many people can recover. In some situations the mortality rate is a devastating 90%, but in other situations the mortality rate is much lower. We can talk about a cure when we have a drug that, when we give it, most people get better, but we are not in that position yet because all of these drugs are still experimental.

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