Tag Archives: Ebola

Ebola: Family Members Versus Healthcare Worker Exposures and PPE

A friend of mine raise a question that I am willing to be is on a lot of people’s minds. Why is it that we have two cases of Ebola in healthcare workers (HCWs) who were wearing personal protective equipment (PPE) but haven’t seen it in family members or other close contacts without it?

It would be worth a short discussion about the different modes of disease transmission that are considered in healthcare settings.

  • Contact: These are diseases that are spread through direct contact with blood and body fluids. This is the case for Ebola at present.
  • Fomites: Fomites are inanimate objects that can be involved in disease transmission. These are surfaces that could have become contaminated with microorganisms via body fluids or even via coughing or sneezing. This is why surface disinfection is so important.
  • Droplet: These are diseases that are spread through large particle droplets that are expelled through normal breathing, coughing, and sneezing. Generally, this type of transmission occurs withing 3-6 feet of the person who is sick. Influenza is a good example of a disease that can be spread this way. Droplet precautions are recommend for Ebola patients.
  • Airborne: These are diseases where the particles are so small that they can remain aloft in the air over great distances or be spread through buildings by air handling systems. Measles and smallpox are good examples. Ebola is NOT spread via this route at present.

Since Ebola is primarily spread through direct contact or through fomites that have been contaminated with blood and body fluids, the family was at lower risk than the HCWs for exposure, assuming that PPE was used correctly. Remember that one of the reasons it has historically been a big problem in Africa is due to funerary practices where the families normally wash the body at some point after the death. Islam also requires a same gender family member to wash the body before burial. Here are the percentages of the population in the currently affected countries that practice Islam to put it in some perspective about deeply entrenched this practice is within those countries that are currently affected in  Africa:

  • Guinea: 50%
  • Liberia: 12.2%
  • Nigeria: 50.4%
  • Sierra Leone: 71.3%

That should provide some context as to why there was much more spread in families in Africa but it still doesn’t address what happened with the HCWs in Texas.

I suspect a more important question is around whether or not there was appropriate training and/or use of PPE. The guidelines from Médecins Sans Frontières (MSF), also known as Doctors without Borders, for PPE use in Africa to deal with this varies from those of the CDC in how this is done domestically (the CDC guidelines for managing this in Africa are oddly different).

In my opinion, there were likely one of two routes of exposure for the HCWs. First is the one that has been reported on in the media. Removal of PPE (doffing) can be very difficult to do properly without cross contamination. During other outbreaks, recommendations have been made to have a trained observer to ensure that there weren’t any breaches in technique because it is so difficult. This also is further compounded by becoming very hot and tired while wearing this level of PPE along with the emotional strain that is likely in caring for these patients. However, current guidelines (2007) for PPE removal do not address this in great enough detail for Ebola (see page 135). These are the directions that are linked to from the CDC infection control precautions guidelines for Ebola in US hospitals.

The bigger problem that hasn’t been discussed in the media is what we use for PPE. In hospitals in the US, we generally use fabric based barriers for contact precautions. These usually do have some water resistance and some are waterproof, but this is very different than using plastic or rubber barriers like are used by MSF. The current recommendations are not aggressive enough in that plastic barriers are only recommended for suspected splash exposures.

There is a phenomenon called strikethrough when fabrics are wet. This is something that is a bigger consideration historically when evaluating surgical drapes. Essentially it is the propensity of microorganisms to pass through fabric when wet because they are much smaller than the gaps that are created by the fibers on the microscopic level. This is even more true for viruses since they are considerably smaller than bacteria.

A fluid resistant gown is not an adequate barrier. These guidelines should include a plastic apron. In addition, shoe covers are optional unless there is suspected exposure to blood and body fluids. In my opinion, this poses a very significant gap as well that could pose future problems. For comparison, look at some of the process in Africa. In particular, watch the second video titled “Taking Off Ebola Protection Gear.”

I don’t know the specifics of the types of PPE that were used in Texas nor their protocols for donning and doffing, but based on my experience in this field this is probably where the breaches occurred that led to HCW exposures. Hopefully we will have learned from these mistakes and get better at this in the future.

ADDENDUM (10/22/14)
The CDC has updated its guidance and includes what I had addressed above.

Ebola and Air Travel

Lately there is a number of questions about the efforts to screen passengers and ban air travel. Will these efforts be sufficient?

Passengers are getting screened who are coming from countries with Ebola (Guinea, Liberia, and Sierra Leone). This is being done both via laser thermometers (a good ideas since this doesn’t require touching anyone) as well as through questionnaires. There are a couple of gaps though with this approach.

First, one must remember that the incubation period for Ebola can run up to 21 days. This is the period of time which a person can be harboring a virus but not show any signs and/or symptoms. A fever is a telltale sign, but unless an individual is three weeks past an exposure to Ebola, this may not be effective in identifying cases. Using a fever alone as a screening tool would not have caught the first case that was diagnosed in the United States. He arrived here on 9/19 but didn’t have symptoms until 9/24.

The questionnaire is meant to identify other risks that may indicate that someone has had Ebola exposure. Like all screening measures, this has some holes as well.

When conducting surveys, there is a common problem with something called recall bias. This is simply because human memory fades both with physiological age but also as events become more distant in time. For example, could you remember what you had for lunch and portion sizes five days ago? What about 21 days ago? These are simply errors that are introduced through poor recollection.

Another problem with screening questionnaires though which is even a bigger issue for this problem is response bias. This is the instance where people will lie in order to achieve their desired outcome, in this case passage on an airline or into a country. This could simply be motivated by the desire to see friends or family or for wanting to conduct business. However, it is not outside of the realm of possibility that someone might knowingly want to bring a disease that they are harboring into another country as sort of a crude human biological weapon.

These screening measures are good, but there are clear gaps. They will be implemented at the five airports (New York JFK, Washington Dulles, Newark, Chicago O’Hare, and Atlanta) with the majority of travelers coming from affected countries. Roughly 150 people enter the US each day from the affected countries and ALMOST all of them enter through these airports.

What about those who come in through other airports? That is a distinct gap. Some people have suggested that we should ban all flights from affected countries. However, that approach has problems as well.

First, airlines are not the only means by which to exit a country. There are land and sea routes as well. Someone who was set on getting to a destination would simply find the path of least resistance into a bordering country and then begin air travel from that location. We’ve already seen something similar happening when some Liberian men were trying to illegally enter the US through Costa Rica. General John Kelly, the commander for South American operations for the Pentagon, raises a very big concern about the problems that will arise if Ebola gets established in South America. People will begin fleeing north to seek medical care in the US. That creates a massive illegal border crossing situation along the Mexican border.

There are even bigger problems with banning air travel. How do aid workers get in and out of a country to help stop the problem at its source? This is one of the big questions I’m asking as I make my decision about whether to go help. I want to know with very little uncertainty that I will be able to leave once my time in field is over. I do not want to get trapped like I’ve entered some massive diseases black hole.

Worse, banning air travel could destabilize already shaky governments in those regions. If that happens, Ebola could spread much more quickly in those areas and be even more difficult to contain, leading to a possible pandemic. That is something we DEFINITELY do not want to see.

There is also a bigger problem emerging now that Ebola has shown up in Lagos, Nigeria. It is the biggest city in Africa with an estimated population of 21 million. It is also an obvious air travel hub due to it’s size. If Ebola gains a foothold in Lagos, we might be too late because of the volume of air traffic through that city.

Air travel from areas hardest hit by Ebola from Gomes MFC, Pastore y Piontti A, Rossi L, Chao D, Longini I, Halloran ME, Vespignani A. Assessing the International Spreading Risk Associated with the 2014 West African Ebola Outbreak. PLOS Currents Outbreaks. 2014 Sep 2. Edition 1. doi: 10.1371/currents.outbreaks.cd818f63d40e24aef769dda7df9e0da5.

Clearly, we have much more to do.

10/15/2014 Addendum:

Back in August, I had started reading Linked: How Everything Is Connected to Everything Else and What It Means for Business, Science, and Everyday Life by  Albert-Laszlo Barabasi on network science and theory because I thought it would give me some insights into how outbreaks behave. Little did I know that this would be useful so soon.

Without going into the technical details, airports are scale-free networks. Essentially, in the real world this looks like larger airports with major airline hubs, significantly more medium size airports with much less commercial air traffic, and finally many small municipal airports with very little major air carrier activity at all. It’s a classic example of this type of network.

I’m going to quote from the book because what he says is important.
“The accidental removal of a single hub will not be fatal either, since the continuous hierarchy of several large hubs will maintain the network’s integrity…Amazingly, most networks of interest, ranging from the Internet to the cell, are scale-free and have a degree exponent smaller than three. Therefore, these networks break apart only after all nodes have been removed–or, for all practical purposes, never.”

This is why closing air travel to a particular country having an outbreak would not likely make much of a difference. Our travel networks are robust. Between land, sea, and air, there are many alternate routes for people to travel with whatever microorganisms they may harbor. I think the way that this applies in this case is that the only way to stop spread via transportation hubs would be to stop ALL transportation hubs in a much broader scale than to that of a few countries. That is simply not economically and possibly ethically feasible.

It’s easy to want to say that we should do that in all of the affected countries. However, I think people would have a hard time making that kind of statement when it affects their own, as it has now in the US.

Ebola in the US – Background

Ebola SEM

I’ve been having a number of friends contact me wanting to know both my thoughts about the emerging Ebola epidemic as well as asking questions about it. It finally reached a point where I realized it would be easier to write about it openly and maybe give people my views on this situation, which are strictly that, MY views. It doesn’t mean they are correct and don’t represent those of any organizations with which I’m affiliated. I’ll give a brief overview of the history of the first case in the US and then will likely post separate items as different questions get asked or other notable stories and/or ideas come to mind.

This interest began when a Liberian man was diagnosed with Ebola at Texas Health Presbyterian Hospital in Dallas. I think that was when the public finally understood just how serious a problem has been emerging in West Africa. People have come to realize that air travel no longer makes the Atlantic Ocean that big anymore. The concept of a global village became very real in a number of people’s minds as a result.

Ebola Distribution Map

Ebola Distribution Map

The timeline is pretty interesting and shows some of the gaps in our system:

9/15 The patient tried to bring a friend to a hospital in Liberia for care who had Ebola. They took a cab and he carried her when she was too weak to walk. Obviously that would qualify as very close contact. They tried multiple hospitals but were turned away. They eventually returned home where she eventually died.

9/19 The patient flies from Monrovia, Liberia to Brussels, Belgium. From there he continues the next leg of his trip to Dulles airport in Washington, DC.

9/20 He continues from Washington to Dallas, TX.

9/24 (Wednesday) He becomes symptomatic. This is a crucial piece of information because Ebola does not spread when a person is symptom free. That means that nobody aboard the flights or might have passed him in the various airports has anything to worry about. (At this point, Ebola is only spread through direct contact. This is technically referred to as contact transmission and if you pay attention in hospitals you will see signs that say “Contact Precautions” or “Contact Isolation” in some rooms. It should be noted that this doesn’t indicate an Ebola patient is in the room, there are other conditions that are only spread through direct contact. A common one in hospitals is MRSA).

9/26 (Friday) He has become sick enough to seek medical care at Texas Health Presbyterian Hospital. Somehow there was a breakdown in communication and the vital information that he had just come from Liberia didn’t make it to the right people. This was a major failure in communications given that there had been guidance to hospitals on identifying potential Ebola victims. I would assume that the hospital is conducting a root cause analysis to determine where there gaps were that allowed this breakdown and that there will be some remediation steps taken to prevent those kinds of errors from being made again. It would even be better if they are transparent with their findings so other hospitals can learn from the problem and analyze their systems for any similar gaps.

9/28 (Sunday) Dallas Fire and Rescue brings the patient back to the hospital via ambulance. I once worked in an ambulance with a patient with active tuberculosis that had not been diagnosed and remember the trepidation I had after I found that out. I can’t even imagine what is going through the minds of this crew.

9/30 (Tuesday) The patient tests positive for Ebola. The CDC holds a press conference that afternoon. I’m pretty certain that a number of people in public health and health care roles uttered a collective “Oh S***.”

At this point public health kicks it into full gear and starts its investigation, a core component of which is called contact tracing. This is trying to identify everyone that might have had contact with the patient. The disease has an incubation period of 2-21 days, which is the time it can take from being exposed to developing symptoms. It should be noted here again that until someone is symptomatic, they will not spread the disease to others. Currently there about 100 contacts identified.

That’s the basic story. Watch for subsequent posts for additional thoughts and analysis.