Although the false alarms might continue for a few more weeks, we have obviously transitioned into the lessons-learned phase of the Ebola non-outbreak in the US. I will list those lessons below, but first, a useful summary of a talk I attended on the evening of Tuesday the 4th.
[Readers needing background may refer to the earlier members of this series, Don’t Panic: Against the Spirit of the Age; Don’t Panic: A Continuing Series; and Don’t Panic: A Continuing Series – Ebola or Black Heva?]
The venue was the Johnson County Science Café, a monthly forum sponsored by Kansas Citizens for Science. Johnson County is, by some measures, the wealthiest county in the country outside of the DC and NYC metro areas; greatly simplifying, this is a product of a somewhat unique combination of blue-state salaries and red-state cost of living. Kansas Citizens for Science was founded in the wake of upheavals on the Kansas Board of Education, which resulted in the initial imposition of, and subsequent drastic changes to, science-curriculum standards for public primary and secondary schools for ~300 school districts half a dozen times between the early 1990s and mid-2000s. The most famous was a 1999 board vote to remove key questions about the historical sciences (including astronomy, geology, and paleontology) from assessment testing, but there were several others which either re- or de-emphasized those sciences as the makeup of the board fluctuated with each election. After a decade and a half of chaos, as of now the board is relatively quiescent – its makeup was ironically substantially unaffected by this month’s wave election – and teaching and testing of the historical sciences is in place. I know several of the key personalities involved, and could certainly tell some interesting stories, but that controversy is not the subject of this post.
The speaker was Catherine Lindsey Satterwhite, PhD, MSPH, MPH, an assistant professor at the University of Kansas Medical Center, itself the setting of one of the recent false alarms. What follows are significant facts from her talk, grouped by topic rather than merely listed chronologically.
Ebola, named for a river in the Democratic Republic of the Congo (formerly Zaire), was first identified in 1976. There are five virus species, one of which, Reston, causes illness in nonhuman primates only. The other four (Bundibugyo, Sudan, Tai Forest, and Zaire) infect humans. Ebola has an animal reservoir, probably bats, but can also be hosted by primates. As has become rather well known recently, EVD is a severe, multi-system syndrome characterized by vascular system damage and impairment of the body’s self-regulating ability; hemorrhaging is common.
First, the non-problems:
- The “source patient” has been identified as a 2-year-old who contracted the disease last December, probably from bat droppings.
- A bushmeat vector occurs during hunting and processing, but due to the fragility of the virus, there is no risk from cooked bushmeat, even if it has only been cooked at low temperature. Since raw bushmeat is dangerous, however, there has been a significant microeconomic effect on bushmeat vendors.
- Ebola’s fragility makes it easily killable with reduced chlorine solution. Dr Satterwhite did not mention the Kikwit outbreak in this connection, but in 1995 an Ebola outbreak there (the city’s population is now 400,000) was suppressed largely through liberal application of bleach.
- Similarly, there is no risk from Ebola virus in the water waste stream. Normal processing of waste will kill it. I note that this demonstrates the absurdity of the widely-promoted hysteria over a parking lot at The Ivy Apartments in northeast Dallas being hosed down after Thomas Duncan vomited in it.
- Indeed, a majority of potential transmission can be prevented by simple frequent handwashing; people mostly self-inoculate with the virus by touching an infected surface and then touching their face, etc.
Hospitals in the US have entire rooms that can heat up to autoclave medical waste, eliminating it as a transmission vector.
- All known instances of transmission have occurred during the symptomatic phase, 2-21 days after exposure. If anything, 21 days is on the long side, so no change to that standard interval by the CDC should be expected.
- A point which cannot be overemphasized: infection requires direct contact with bodily fluids, contaminated objects, or infected animals. Direct contact is defined as within 3’/1m. Walking through a subway station, for example, does not constitute direct contact. If someone sitting next to you sneezes and you catch what they’ve got, that’s direct contact, not airborne.
- Speaking of which, there’s a lot of confusion about what “airborne” means. Successful transmission through, for example, the HVAC system of an office building, as routinely happens with seasonal flu virus, would be considered airborne. You can’t get Ebola through air, water, or food.
- It is extraordinarily unlikely that any species of Ebola will mutate to an airborne form. This would require many mutations of just the right type occurring in just the right sequence; as Dr Satterwhite said, “Ebola becoming airborne would be like me growing wings tomorrow.” I would ask: do you worry about rabies virus becoming airborne? By the way, there is no evidence of EVD transmission through domesticated animals.
- Ebola virus has a low R0 value, which only needs to be modestly reduced to contain an outbreak. The R0 of every known Ebola species is 2, closely comparable to hepatitis C, significantly lower than HIV or SARS, and far lower than mumps or measles.
- Significantly, a weakened immune system makes it more likely to contract EVD. I (again) note the prevalence of helminth infections in the Third World and its rarely-acknowledged role in the incidence of HIV there.
- Ebola dies within hours outside of fluids, living carriers, or the recently deceased, and it clears the system; unlike HIV, when you’re over it, it’s completely gone. There doesn’t seem to be any long-term damage to those who have recovered.
- There are established, if arduous, procedures for identification and isolation of existing cases, contact tracing, and monitoring. And the safety of health care workers in West Africa is improving; case counts are actually dropping in Liberia, and there are some signs that the epidemic may be ebbing. I expect that this is multifactorial – Dr Satterwhite specifically mentioned a recognition that cultural practices are a problem, acceptance of different burial techniques, and greater acceptance of health-care workers.
- … which has been facilitated by such simple and retrospectively obvious procedural changes as having someone outside treatment facilities to talk to people, giving people access to areas where PPE (personal protective equipment; “moon suit”) is donned so they can see the person before they put it on, and when someone dies, allowing family members to view the body before it is removed. It’s almost like treating people respectfully elicits cooperation, or something.
The genuine unknowns:
- The mechanism of transmission to West Africa is unknown. EVD wasn’t endemic there before the current outbreak, which is why it was initially thought to be Lassa fever or malaria. I note that the distance from, eg, the aforementioned Kikwit to Guéckédou, the city nearest the origin of the current outbreak, is ~3,600 kilometers by air, across the Gulf of Guinea. A moment with a map establishes that the American equivalent would be some disease endemic to Alaska or the US Virgin Islands suddenly appearing in the Midwest, except without any regular air travel or good roads in between. The probable bat-dropping vector, however, is suggestive.
- Some people have gotten EVD and remained asymptomatic; infectivity of those patients is unknown.
- Plasma from EVD survivors might be a therapeutic agent. This is being attempted primarily among health-care workers. Its effectiveness is unknown.
- Ebola has been a series of mini-epidemics which tend to end abruptly, cause unknown.
- How to balance other infectious conditions endemic to Africa with EVD containment?
The real problems:
- The CDC temporarily closed its special pathogens branch due to earlier mishaps with anthrax and smallpox. This turned out to be really bad timing.
- Attending funerals and contact with case care pose substantial risks.
- Existing drugs and antivirals like Tamiflu® don’t work against Ebola.
- PPE is cumbersome, uncomfortable, and expensive. It takes a long time to put on and take off, it’s too hot to work in for more than an hour or two, and it has to be both sprayed with disinfectant solution and disposed of afterward; it cannot be reused. And there aren’t enough trained health-care workers with experience in PPE.
- More generally, medical waste poses a logistical challenge. Incineration is possible, but autoclaving is more common. As mentioned above, first-world hospitals have entire rooms that heat up to do this.
- ZMapp™, a possible treatment, is hard to manufacture. Current treatment for EVD consists entirely of supportive care: IV fluids, balancing electrolytes, maintaining oxygen status and blood pressure, and treating other infections if they occur. I note that this has been highly successful – for Americans. The overall case fatality rate in West Africa, however, was 36% as of the end of October.
- Media communication has been … problematic.
This is my own list of lessons deriving from the above, to which commenters are encouraged to add:
- Even assuming a novel viral pandemic with a high R0 value, most of the death toll may result from public panic and its associated emergent phenomenon, official overreaction.
- There are significant logistical challenges associated with provision and effective use of medical supplies; hospitals would be well-advised to carry out a Theory of Constraints exercise and stockpile appropriately. NB: “appropriately” ≠ “everything you can think of.”
- For reasons of both technology and political overhead, the vaccine-development pipeline is too long (two vaccines for EVD are in development now). As Drexler wrote nearly three decades ago, one of the best features of nanotechnology is plague insurance. Regular readers of this blog need no persuasion of the desirability of reduced regulatory burdens.
Ebola poses no significant risk in the United States, and neither does enterovirus D68. Relatively novel vector-borne diseases (Chikungunya, Chagas) are limited anyway – Aedes aegypti, for example, can’t survive outside the Southeast, and assuming adequate political will, which would materialize quickly in the event of a serious threat, vector control is entirely achievable. The reason to maintain our lessons-learned database is the possibility of a new Kansas Flu – something highly infectious among and deadly to humans, arising in a first-world country, even our own, and spreading too quickly to be contained.