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.
The CDC has updated its guidance and includes what I had addressed above.