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Ebola’s mortality rate may depend on several factors:

  • The particular strain of Ebola.
  • The age and underlying health of the patient.
  • How ill the patient is when s/he begins receiving care.
  • The quality of the care the patient receives.
  • The availability of antibody treatments such as ZMAPP or serum taken from survivors.

Prior Outbreaks

Before this year most Ebola outbreaks have been confined to rural areas, and treatment has been what was feasible in a tent. The West African epidemic is of the Ebola Zaire strain, for which WHO reports mortality rates from prior epidemics ranging from 44% to 90%. [WHO 9/14]

West Africa

It was initially thought that the mortality rate for the West African epidemic was around 55%. [Reuters 8/5/14]  In September, however, a scholarly article in the New England Journal of Medicine calculated the mortality rate in Guinea, Liberia and Sierra Leone at around 70%. [NEJM 9/23/14]  A Sierra Leone study of 44 patients [Reuters 10/29/14] showed 74% overall mortality, but broke the figure down in illuminating ways:

  • 57% of people under age 21 died, compared to 94% of those over the age of 45. Older patients have greater mortality risk.
  • 33% of patients with less than 100,000 copies of the virus per milliliter of blood at diagnosis ultimately died, compared with 94% of those whose had more than 10 million copies per milliliter. As we’ve previously suspected, mortality is highly dependent on how sick a patient is when treatment starts.

A thrilling anecdote from Liberia is also suggestive: A student nurse named Fatu Kekula cared for four household members, and managed to save three of them, achieving a 25% mortality rate. [LA Times 10/6/14]  She avoided infection herself using a resourceful combination of surgical gloves, plastic bags, raincoats and copious amounts of chlorinated water. Critically, she was able to give them IV drips, and she was on call essentially 24/7. What happened to any four patients has no statistical significance, but the demonstration that such a good outcome is even possible is heartening.

Nigeria

Nigeria had an outbreak sparked by a single air traveler from Liberia. Despite many high-risk contacts — and many incidents of quarantine-breaking and other misconduct — in the end there were only 19 cases, of which 7 died, for a mortality rate of just 37%. [WHO c.10/15/14] The number of cases is small, so this figure isn’t too statistically significant. One may speculate, however, that the lower mortality rate in Nigeria reflects two main factors: (1) better quality of health care, and (2) the fact that many patients were being monitored daily, so were presumably given care as soon as they began showing symptoms. The single patient who traveled to Senegal survived, and the child who traveled to Mali died, but neither case tells us anything about overall mortality rates.

The U.S. and Europe

The number of cases treated in western countries is also small, so even less statistically meaningful than the figure for Nigeria. As in Nigeria, most of these patients received treatment as soon as symptoms were noticed, which may be a significant benefit. Disregarding patients still in treatment, the figures, from the excellent New York Times Ebola Facts page, are as follows:

  • United States: 8 patients, of which 1 died and 7 recovered, for a mortality rate of 13%.
  • Europe: 8 patients, of which 3 died and 5 recovered, for a mortality rate of 38%.

Since the figures are so small the difference between Europe and the U.S. could easily be random. But it’s interesting to note that Thomas Eric Duncan, the patient who died in Dallas, had initially been turned away by the hospital, and only started receiving care after he had become so ill that he had to be transported by ambulance. His two nurses, in contrast, began receiving care soon after they first developed fevers, and both have recovered fully. CNN’s discussion of the factors that affect survival in western countries is a bit dated but still worth a look: [CNN 10/20/14]

Dr. Paul Farmer, a Harvard professor and co-founder of the charity Partners in Health, has expressed the hope that with top-notch care the mortality rate for Ebola could be as low as 10%. [London Review of Books 10/23/14] This isn’t inconsistent with the U.S. experience, keeping in mind the low sample number. It will be wonderful if it proves possible to substantially reduce the mortality rate in the African setting. An improved standard of care would not directly help stop the epidemic, but it would indirectly contribute to stopping transmission if it encouraged more people to enter clinics rather than staying at home, which increases the risk of infecting other household members.

Added 10/31/14: Paul Farmer’s emphasis on quality of care implicitly criticizes the way some twenty Ebola outbreaks have been handled since 1976, most notably by Médecins Sans Frontières / Doctors Without Borders (“MSF”). I would characterize the MSF approach as embodying three priorities:

1. Stop the Outbreak, by Isolating Patients.
2. Protect Staff from Getting Infected.
3. Cure as Many Patients as Possible.

For nearly 40 years MSF has been stunningly successful at achieving these goals, often in remote rural settings with extremely limited infrastructure. I’m sure Dr. Farmer would hasten to agree that we owe MSF and its peers an enormous debt of gratitude for their extraordinary service to humanity.

My own view is that MSF’s priorities are correct. Stopping the outbreak must always be job #1. One wants also to minimize risk to staff, but some risk is inevitable and must be accepted in order to end an Ebola outbreak. Curing patients is every doctor’s objective, but if a choice must be made stopping the epidemic is more important. Similarly, if staff start becoming infected at excessive rates we would lose the ability to either stop the outbreak or cure patients.

Saying that these priorities are correct does not, however, answer the question of how much can and should be done to cure patients.

My understanding, for example, is that MSF typically does no blood work apart from an initial test to confirm the diagnosis and final tests to confirm a cure. Often there would be no lab available to do additional testing anyway; it’s difficult and risky for a staff member wearing goggles and three layers of gloves to take a blood sample; puncturing the skin of an Ebola patient can lead to infection and/or uncontrolled bleeding; getting a blood sample takes precious time away from other patients; blood tests would cost money that might be better spent elsewhere; etc. etc. When regular blood tests are available, as in western hospitals, care can be customized to the patient’s individual needs. Infections can be identified and halted; imbalances in electrolytes identified and corrected, etc.

I presume that MSF would agree that a higher standard of care would be desirable, wherever it is feasible. The real question in each situation is where do you strike the balance between an aspiration for the best standard of care and the need to quickly isolate patients to stop the outbreak, as well as constraints of money and infrastructure. It may be that the MSF approach should be implemented quickly as soon as an outbreak is identified, then upgraded as time and resources permit.

Dr. Farmer’s push for a higher standard of care is directly opposed to a recent WHO proposal for “clinics” that would isolate patients but offer little or no medical care. [AP 10/2/14] This is a desperate response to the situation in Monrovia several weeks back where patients were being cared for at home — often infecting many household members — because there were no beds available. Since there now appear to be open beds it may be hoped that we don’t have to do in this inhumane direction, which explicitly sacrifices patient care to the overriding goal of stopping the epidemic.  [Economist 11/1/14]

Antibody Treatments

A handful of U.S. and African patients received the few available doses of ZMAPP, an artificial antibody treatment that has been successfully tested in monkeys. The U.S. patients survived and several of the African patients died, but the numbers are too small to reach any conclusions about its effectiveness. Similarly, several U.S. patients received antibodies in serum taken from survivors. The fact that they survived is encouraging, but again the numbers are too small at this point to support conclusions.

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What can be done? This post will make some suggestions.

1. The first priority is to reduce the rate of transmission through known channels, which I discussed in detail in my previous post, The Ebola Chain Reaction.

Home Caregivers. Education is the first need: people need to know Ebola’s symptoms, then they need to know what to do if someone in their household starts to display them. This is an extremely hard problem. The early symptoms of Ebola — fever, vomiting and diarrhea — are indistinguishable from many other endemic diseases. Every person with a fever can’t be taken immediately to the hospital, and in the meantime the home caregiver is in no position to use any semblance of anti-infection protocol. In a crowded household people share the same spaces for eating, sleeping and every other aspect of life. Practical advice for home caregivers needs to be developed and communicated. That advice should include how a patient can be cared for in the home with reduced risk, when a patient should be taken to a clinic or hospital and how to decontaminate living spaces after a patient has left. But I don’t see how the risk of transmission to other members of a household can be much reduced, especially in poor, crowded housholds.

Healthcare Providers. Sooner or later — hopefully sooner — a symptomatic patient will be brought to a clinic or hospital. Again and again patients have infected multiple hospital staff members, and even forced the hospital to close for decontamination. As the numbers of patients increase this cannot be allowed to continue. Emergency rooms must be organized and staffed so that an Ebola patient can be identified and isolated without endangering staff or other patients. That’s easy to say but really hard to make true. Can we expect emergency room staff to wear bio-hazard suits? Can each patient be kept apart from other patients until they have been assessed? And again the problem arises of distinguishing early stage Ebola from other diseases. A quick, cheap and accurate test is needed to enable healthcare providers to distinguish who does or doesn’t present an Ebola risk. Airports are starting to use infrared detectors to cull out people who are running fevers, but it’s hard to imagine similar gear being deployed to all the relevant hospitals and clinics, and even if someone has a fever a hospital — unlike an airport — can’t just turn the patient away; but knowing who does and doesn’t have a fever might be helpful. And of course healthcare providers need the training and gear necessary to safely care for Ebola patients.

Traditional Funeral Practices. African funeral practices spread infection widely and must be suspended. This is a very difficult problem, since funerals are one of the ways people deal with the powerful emotion of grief. They will resist changes, and unless physically prevented are likely to model the behaviors they have seen and performed in the past. Culturally-specific strategies must be devised and implemented to encourage people to mourn Ebola victims in ways that do not place them at risk of infection.

These three transmission modes are quite capable of keeping the epidemic growing, with an Effective Reproduction Rate (Re) of more than one (as discussed in my last post). Pushing each of them down as low as possible is the first priority.

2. New modes of transmission are possible in the urban environment. Prior outbreaks have all been in rural areas, so there is no past experience with the additional ways Ebola can spread in a city, especially in crowded areas.

The first question is how important any new urban modes of transmission are, i.e. how much of a contribution they make to Re. If any urban mode of transmission is comparable to the known modes it needs to get similar priority, but if urban modes of transmission are more theoretical than real they can be deprioritized. The contact tracing process generates a tremendous amount of information about exactly what kinds of contacts did and did not lead to infection. Contact tracing information from all countries should be collected and analyzed, and conclusions should be shared amongst Ebola fighters. Communications to the public should generally be accurate, but in the public interest may not always be “the whole truth.” Significant modes of urban transmission that are so identified must be countered, if possible.

Even before data is available it makes sense to analyze urban life and make changes that seem logical and have the potential of being cost-effective.

  • Replacing shaking hands with fist bumps is a step in the right direction, although elbow bumps or just bows would be even better. Air kisses between friends and colleagues (if that was ever an African thing) can be suspended for the duration.
  • Situations where people are crowded into direct contact are part of urban life, but present an obvious risk. People can be cautioned to avoid crowds and steps can be taken to reduce crowding in taxis and buses. Update 9/8/14: This chilling item from the Wall Street Journal suggests that taxi drivers and surfaces in taxis could easily become contaminated by bleeding, etc. Ebola patients. [WSJ 9/7/14]
  • While 60% alcohol hand sanitizer is better than nothing the CDC recommendation is to wash hands with soap and water whenever possible. Sanitizer could have an adverse effect if people use it instead of washing. There is also a question of whether alcohol has much effect on the virus anyway. Update 10/7/14: Since Ebola has a lipid coat alcohol-based hand sanitizer should be effective against it. The CDC continues to recommend alcohol-based hand sanitizer (with at least 60% alcohol) when hand washing isn’t possible. [CDC 10/7/14] Bleach is standard for disinfection, but it’s not clear to me whether dipping ones hands in a shared bleach bucket, as is becoming common in some affected cities, is a net benefit.
  • Some offices are taking people’s temperatures when they enter, and asking them to wear it as a badge. The risk of transmission in an office setting would seem to be very low in any case, but if this serves to raise awareness and control anxiety it may be worthwhile.
  • Closing schools initially seems logical, but it imposes social costs and might turn out to be an overreaction. School children are somewhere doing something, probably with other children, when they aren’t in school. It might actually be better to open school, with provisions to minimize physical contact, and perhaps also with a process for taking each student’s temperature as they arrive and sending home anyone with a fever.
  • Other situations in which people put their hands on one another deserve consideration. Massage parlors and sexual contact come to mind. And a panicky post worries about barber shops (not without reason).

Amongst all these possible risks and countermeasures, public communications should focus on the most important transmission modes and the most important countermeasures, based on the best available information at each point. On the other hand, worthless countermeasures, or countermeasures against trivial risks, may be ignored if they afford comfort and don’t unduly draw attention or resources away from more important issues, or lead to a dangerously false sense of security.

3. Superstition, rumors and mistrust must be countered and overcome. The West African Ebola fight has been plagued by these factors from the outset. In addition to the usual superstitions about causes and folk remedies the rumor spread that Ebola was brought by the healthcare personnel who were in fact trying to stop it. MSF had to withdraw from more than two dozen “red villages” because this hostility made them too dangerous. The poor and crowded West Point district of Monrovia attacked and ransacked a quarantine facility that had been sited there. In part this reflected “Ebola denial” which will disappear on its own as the epidemic makes itself felt more widely. But it also reflected mistrust and irrational fear that must be countered.

4. A pattern of quarantine breaking and lying must be broken. Again and again, especially among the privileged classes in Nigeria, people have broken quarantine and/or lied about prior contacts with Ebola cases, thereby putting dozens or hundreds of health care providers and other contacts at risk. (For details see my post, Arrogance and Privilege Imperil Nigeria’s Attempt to Contain Ebola) This reflects arrogance and a habit of getting their own way regardless of consequences to others. The immorality of this behavior — and its dire consequences — must be brought home to everyone, at every level of society. This is culturally-specific but one imagines that achieving this goal might involve use of media and involvement of religious and other thought leaders. It is hard to see how Nigeria — or indeed any society, including developed countries — can control Ebola if a pattern of quarantine breaking and lying like the one we have seen so far should persist.

5. Adequate healthcare facilities are essential to allow Ebola patients to be cared for outside the home, where they are much more likely to pass the virus along to others. The epidemic has consistently outstripped available facilities, and unless there is a marvelous international intervention this seems doomed to continue. Healthcare is also key to minimizing the death rate, which is important as a humanitarian matter even though it is only tangentially relevant to stopping the epidemic. Sadly, there is no possibility of replicating the level of care the two Americans received at Emory, which no doubt contributed to their recoveries. But any lessons learned in developed hospitals about how best to manage Ebola patients should be made available to African healthcare providers. Most important are any recommendations that it might be possible to implement in an overstressed and impoverished facility.

Updated 10/7/14: Here is a new idea that might make an important contribution, even though it’s really distasteful. Sierra Leone plans to build up to 1,000 “makeshift Ebola clinics” that would offer little, if any, treatment. [AP 10/2/14] These “clinics” would really be hospices which would let people die and be safely cremated or buried without infecting their families. It’s dreadful to think of abandoning people who could be saved with minimal care. But just at the moment this may be the least bad alternative, since if the patients die at home they will very likely infect their caretakers and some or all of the other members of their households. If enough of these facilities could be provided, and if people could be persuaded to use them, this could be a game changer.

6. Outsiders must send money, health care and infection control materials, healthcare workers and healthcare trainers. Happily — if far too late — the world finally seems to be waking up to the gravity of the situation, and to its own moral obligation to help, as well as its self-interest in stopping the epidemic before it affects even more countries. Individual readers can find a list of ways to help at the current Ebola Report post. Charity Navigator can help you assess the quality of charities that are fighting the epidemic. Doctors Without Borders USA, for example (the U.S. branch of Médecins Sans Frontières) gets the highest ratings for both use of funds and accountability/transparency.

7. Immunity is the ultimate weapon against disease, and in this case it may be the only way the epidemic can be stopped. Obviously, testing of a vaccine must be given top priority. People who have recovered from Ebola are also an important resource. It might be possible to recruit recovered Ebola patients to play roles in healthcare settings, such as hospital emergency rooms, or in other situations where their immunity could come in handy. Recovered patients may also offer a source of antibodies that could be purified as a serum to help current victims. Mutation is the ultimate weapon of disease, and this could undercut both a vaccine and survivor immunity, but as to this possibility we just have to hope for the best.