About the Ebola Virus
There has been a lot of press related to the Ebola Virus and much is difficult to take in and process. Gary and I were talking about this a few days prior to my first of now 3 sessions of training for an Ebola case coming into the hospital at which I practice. I’m not an infectious disease specialist, but I, like all of my colleagues, have had both biological education and mandatory preparatory training sessions. I shared some of this with Gary and he felt it might make for a good post on the NAT-SAFE website.
Let’s start with some of the biology of the virus. It was first discovered not in Africa but in East Germany as the Marburg virus in 1967.It is in a family of viruses known as Filoviruses.The name stems from their strand-like or hair-like appearance microscopically. For those interested in the technical biologic details, it is a negative sense single stranded RNA virus.These viruses can cause disease in both higher primates and man.The illnesses are classified as hemorrhagic fevers.
The Ebola virus exerts a multi-pronged attack on the host’s immune system. It is capable of shutting down some of our naturally occurring defenses such as interferon and it kills lymphocytes which are a type of white blood cell. It then causes an exaggerated inflammatory reaction which leads to the fever and tendency toward bleeding that are the hallmarks of the disease.
It is important to separate two features of any infectious disease, namely how contagious it is and how severe is the disease it causes.
In terms of Ebola, it was well known that the disease severity is very high.The overall East African outbreak has had about a 40% mortality rate and in Guinea the death rate it was over 60%. By comparison, the world-wide 1918 influenza pandemic had only a 19% mortality rate. There is no known “cure.” However, good supportive care in terms of hydration, nutrition and vital sign support, appear to lower the death rate considerably. As of mid-November 2014, there had been 10 cases treated in the U.S. with two deaths.
Contagion relates to how many other people contract the disease from an already infected person. Consider the hypothetical situation where the average infected person spread the disease to just 2 people. Those two would then spread it to four. Those four spread it to eight, and so forth.After just 10 such cycles, this would result in a million cases. This is what is really meant by “going viral.” It’s what epidemics are all about. When containment results in each case passing the disease to less than one other person, the spread is promptly slowed and epidemics are quelled. However, in Africa the spread is still estimated to be around 1.4 to 1.6 persons. The patient in Dallas did spread the disease to two nurses.
The best news from the Dallas experience may be that no cases other than the two healthcare workers were infected. Given that several people were in close contact with the patient prior to going to the hospital, this does suggest it may be a bit less contagious than we had thought and that is a good thing. As more is becoming known about Ebola, there are some good reasons why it may be less contagious than some other infectious diseases.
Many viruses are sneaky. When they infect a person, the person can be sheading large quantities of live virus and thus be highly infectious while still completely asymptomatic. This kind of biologic behavior favors spread the virus. Fortunately for all of us, Ebola doesn’t work that way. Patients do not shed Ebola until they are into the symptomatic phase of the illness, typically about a week into the illness.If they are not symptomatic, they are not infectious. This is also why the Maine nurse who objected to mandatory 21 quarantine was eventually judged correct for objecting to quarantine on return while symptom free.
The key to screening is a positive history of travel to the endemic outbreak area [Liberia, Guinea or Sierra Leone] within 21 days AND the presence of symptoms that are mostly non-specific such as fever, abdominal pain, weakness, muscle pain, easy bruising/bleeding or headache. Direct personal contact with a known infected person may also be a substitute for travel. In this situation, seek medical attention.
Eight hospitals here in Massachusetts have stepped up to the plate and developed capabilities for dealing with Ebola cases developing here. The Centers for Disease Control in Atlanta reviews and certifies hospitals that pass CDC muster. As of now, Baystate Medical Center Springfield, Massachusetts General Hospital in Boston, UMass Memorial Hospital in Worcester and Boston Children’s Hospital in Boston are listed on the CDC website. Boston Medical Center, Beth Israel Deaconess, Brigham and Women’s and Tufts Medical Center are in the process and being reviewed. The Department of Health has already developed the capacity for rapid turnaround laboratory testing. The Massachusetts General Hospital actually put their plan into action about two weeks ago for a suspected case who eventually tested negative.
I want to make a few comments regarding person protective equipment [PPE]. If one must come in close contact with a potentially infected person, PPE is needed. The form this takes is different from the PPE used when actually caring for a known and ill patient who actually has Ebola. One of the keys to putting on (donning) and taking off (doffing) PPE is having a second observer watching. From my own personal experience with training, it is much easier to err on taking PPE off (doffing) than putting it on (donning). Also it is important to remember that once you’ve had contact you must consider every surface of your PPE contaminated. The doffing process is to from clean to contaminated items. For example, when double gloved, one removes the first of the four gloves by slipping fingers between the two gloves on the opposite hand. That exposes a “clean” glove. That glove is used to remove top glove on the opposite hand, possibly contaminating it in the process. The clean lower glove removes the final glove on the first hand and then the bare hand removes the second and remaining glove from the opposite hand. One of the gloves broke during my training so this is not nearly as easy as it seems. It is definitely worth practicing. The key is to have a second person serving as an observer to detect breeches in protocol. Recall that the two cases in the U.S. occurred as passage to healthcare worker not a household contact.It is definitely possible that some failure in proper use of PPE contributed to the passage of the virus. The CDC in conjunction with the Johns Hopkins School of Medicine has several very detailed training videos on the CDC website. [ http://www.cdc.gov/vhf/ebola/hcp/ppe-training/index.html]
The details of decontamination are both beyond what I can get into a brief primer and beyond my level of expertise, suffice it to say that the Ebola virus is quite susceptible to ordinary bleach and this remains the key cleansing agent.
Finally, the CDC website has a lot of information available and is a superb authoritative source. As well, searching the New England Journal of Medicine website for Ebola turns up several very good free resources many of which are readable without advanced medical knowledge.