It is after a review of current MSF recommendations for PPE, that we considered writing a deeper treatment of the issue regarding Ebola transmission. We thank Josh Scholnick for his important observation that MSF is indeed recommending the use of N95 masks for Ebola in the current West Africa epidemic [see the comments section of the prior post]. So, let's take a step back and re-review the facts:
- In 1995, we had what was the most disruptive event signature pattern for Ebola documented during the 1994-present time frame. This was the Kikwit, DRC outbreak, which was due to Ebola-Zaire (the same strain observed in the current epidemic):
Caption. Epidemic curve from Khan AS, Tshioko FK, Heymann DL, Le Guenno B, Nabeth P, Kerstiëns B, Fleerackers Y, Kilmarx PH, Rodier GR, Nkuku O, Rollin PE, Sanchez A, Zaki SR, Swanepoel R, Tomori O, Nichol ST, Peters CJ, Muyembe-Tamfum JJ, Ksiazek TG. The reemergence of Ebola hemorrhagic fever, Democratic Republic of the Congo, 1995. Commission de Lutte contre les Epidémies à Kikwit. J Infect Dis. 1999 Feb;179 Suppl 1:S76-86. May 12, 1995 was the date when substantive international response was initiated (i.e. effective infection control measures were implemented). The beginning of the available event signature was via open source media on 5/9/14, where the accuracy of the assessment was maximized on Day 7 of the signal at an IDIS Cat 6 (disaster). Note the trend of resolution of social disruption (IDIS categorizations) over time, which is what has been observed for every Ebola crisis and disaster up to 2014, except for the current situation in West Africa. Event signature pattern courtesy of Ascel Bio, Inc.
- At that time, MSF was the lead organization for medical care, and they were using standard surgical masks [see MSF's manuscript, noting the "shopping list" on Table 1]. Here we note that surgical masks do not protect from aerosol transmission of pathogens. Tuberculosis, for example, is transmissible by aerosol route, hence the need to wear an N95 mask for that pathogen. MSF was then, as they are now, the world's experts in field clinical management of Ebola. And at that time, they did not advocate the use of "space suits", PAPR, or other exotic respiratory gear beyond the surgical mask. Note the epidemic curve for healthcare worker infection was brought down to zero cases shortly after MSF's involvement. Their intervention was heavily focused on barrier nursing technique and not on the use of PAPR or N95 masks.
- During this time, researchers in BSL-4 laboratories such as at USAMRIID were utilizing positive pressure "space suits" with sophisticated respiratory apparatus to protect against any possibility of inhalation exposure while working with Ebola Zaire. This was heavily influenced by USAMRIID's experience dealing with the Reston, VA epidemic in a primate facility of Reston virus. There it was strongly suspected Reston could be transmitted by air, and probably by aerosol among the primates in the facility. There was also notation of human exposure without apparent clinical infection, which heightened concerns that other members of the Ebola family (i.e. the Zaire strain) could also be transmitted in a similar manner. But, no one had been able to prove this in the field. As noted above with Kikwit, had the agent been transmitted by aerosol, we should have seen continued healthcare worker infection. Yes, everyone was aware of purported experiments in the bioweapons community that Ebola Zaire could be aerosolized in the air space of a primate, with successful infection. However, under natural conditions in Africa, this was not observed.
- Understandably, the USAMRIID scientists, who this author considers a lost national treasure, worried publicly to the media about the potential for Ebola Zaire to be capable of "airborne transmission" and thus, having "pandemic potential". It is certainly an understandable worry. Particularly when they worked so closely with this highly lethal agent for so many years.
- Over the years, this meme of "potential for airborne transmission... and therefore pandemic potential" was picked up by popular authors and media figures such as Richard Preston, Laurie Garrett, and Michael Osterholm. These individuals have been savvy to the American culture's lust for sensationalism, and they made their careers off this meme as it was applied to avian influenza (H5N1, H7N9, and so on), SARS, MERS, and seemingly every clinically significant, newly "discovered" virus since. The accelerant for their continued transmission of this meme has been the proliferation of advanced laboratory diagnostics, where the world is now able to give a name to viruses that have probably been present for thousands of years.
- And academics began to pick up on this trend, exploiting every publicized public health crisis with further claims of "potential for airborne transmission... and therefore pandemic potential". In this manner, they are not selling books (in the case of Preston and Garrett) or 3M products (in the case of Osterholm), but they are selling their brand of research. So, this author has personally been on the receiving end of Fox News, for example, where an academic making these claims was played against what this author hoped was fact and logic. Fear and sensationalism sells in America, which is unfortunate.
- And, of course, we have had several studies demonstrating the potential for airborne transmission of Ebola-Reston and Ebola-Zaire be taken out of context and used to further propel the above-mentioned "airborne" meme. The problem with these studies is they simply did not marry up with what has been for decades and is being oberved now regarding the actual transmission dynamics of Ebola-Zaire (regardless of us now dealing with the most heavily mutated virus ever documented). So yes, the potential is there, but we have not seen this in the past, and we are not seeing this happening now. And we need to focus on the now.
- Now, let's talk about the basic reproduction number (Ro). This is a mathematical expression of how "contagious" an infectious disease is. Ebola-Zaire, when it appeared in Kikwit in 1995, was believed to be associated with an Ro of 2.7. Currently, the Ro in West Africa for Ebola-Zaire, despite it being the most heavily mutated Zaire strain ever documented in history, is estimated to be less than 2.7. For comparison, all of these diseases are more "contagious": influenza (Ro= 2-3), HIV and SARS (Ro= 2-5), mumps (Ro= 4-7), smallpox, polio, and rubella (Ro= 5-7), and whooping cough and measles (Ro= 12-18). It is ironic that America's nursing unions are calling for universal availability for PAPR, yet are the #1 healthcare provider group who refuses to protect their patients by vaccination for seasonal influenza. PAPR, it should be noted, is next to impossible to stockpile at a national level. N95 masks are difficult to stockpile because they are based on appropriate fitting.
- And let us not forget the publicly reported facts here in the US: that the pre-admission Ro for Dallas was zero; and the post-admission Ro was 2. We note that Duncan was vomiting at home and yet none of the original contacts during that chaotic time became infected. The Ro for both Nebraska and Emory, following multiple rounds of admissions has been zero. The Ro for New York City is currently zero.
- It is important to acknowledge, as this author has here before, that Ebola is a very scary proposition for any healthcare aid worker going into West Africa right now. Despite the fact this author worked for a brief period of time in Cote d'Ivoire collecting ecological specimens for Ebola using nothing more than a surgical mask, the prospect of exposure for a healthcare worker is different (see below). It is the prospect of splash risk and the miniscule chance of inhaling a droplet of infectious fluid that causes concern for those who work with patients. While imperfect, fever is the most frequently documented finding, but during a time point in the illness when the patient is not expelling high volumes of highly infectious fluid. It is imperfect because not all patients exhibit fever when infected with Ebola- but we have known this since the 1970s. The evidence of extremely low potential to infect others is here in the US- again, the experience of Dallas with the pre-admission contacts, the nurse who was febrile but was on an airflight, and the NYC physician who rode the subway and went bowling with friends. In no instance was anyone infected.
Caption. Documentation by the WHO Ebola response team in the mid-1970s of Ebola symptoms over time. The period of greatest risk of infection is when the patient is expelling high volumes of highly infectious fluid, as noted by the red box.
- It is also important to acknowledge this author in July offered to help backfill for Kent Brantley at Samaritan's Purse's Monrovia Ebola clinic. However, hedging his bet given the unprecedented size of the epidemic, he opted to bring PAPR with him. This was a reflection of uncertainty at the time regarding the transmission mechanism of the virus. It is also important to point out how inappropriate it would have been to use PAPR when none of the African healthcare workers had access to such protection.
- Lastly, the lethality of Ebola has been much-publicized as it pertains to Africa. If you receive inadequate and delayed medical treatment for Ebola, you may expect a 70-90% case fatality rate. As readily demonstrated here in the US, prompt, expert treatment results in a 100% survival. Even in Africa, survival rates have been driven down to as low as 30% due to aggessive IV fluid and electrolyte management not unlike what you do for a cholera patient.
Summary. The overall observation is overreaction, which is typical for a non-routine, unusual infectious disease crisis or disaster. Particularly when dealing with an agent that a country has never had to deal with before at the community level (as was the case here in the US). Unfortunately, some take advantage of this unraveling of certainty to drive the market or academic research. Unfortunately, this contributes to a movement in recommended PPE guidelines that set a precedent for preparedness that may be difficult to realize. This movement in guidelines contributes to further erosion in public trust, as readily seen here in the US. And, as we have noted several times above, a failure to know one's history means you will be doomed to repeat it.
Is Ebola "airborne"? Sure, under rare, limited conditions. This risk pertains almost exclusively to healthcare providers involved with very close contact with the patient- particularly when dealing with a patient who is expelling high volumes of maximally infectious fluids in the context of vomiting, diarrhea, and the occasional cough. Typically, these patients are not walking around, but are very ill and bedridden. In other words, they would not be flying on airplanes or going bowling.
Is PAPR required for healthcare workers? No. Is an N95 also required? Probably not. Is a surgical mask required? Absolutely- with no skin exposed anywhere on the body. Is reduction in risk of exposure utterly maximized with PPE that includes PAPR and N95? Sure. Will you, the average provider, have such equipment available to you when you need it? Probably not with PAPR. Probably with N95 (albeit there is a limit to the supply). Will you have access to surgical masks? Yes, in abundance. What would this author do, right now, if he had to see a probable Ebola case? He would certainly prefer PAPR, would probably desire N95, but knows that a surgical mask is probably fine.
Does Ebola have "pandemic potential"? Extremely unlikely. By "pandemic" we use the definition of nearly unstoppable global penetrance to every known human community. We expect Ebola to continue shedding into the global air traffic grid, especially if some form of travel restriction is not in place. The US has misstepped in this regard. Yes, we are all worried about a potential "surprise" translocation to places like India, Brazil, or Indonesia.
What is the #1 pathogen in the world we worry about at this moment? It is still a novel influenza virus.
We hope this helps to clarify much of the confusion regarding this important issue. Comments are welcome, and again, thanks Josh.