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Great News From Liberia

The news from Liberia is wonderful: the last known Ebola patient has been discharged from treatment! [NYT 3/6/15] This doesn’t make Liberia “Ebola free” – that requires 42 days (twice the incubation period) with no new cases. Many contacts are still being monitored, and others may not have been identified, so Liberia may still have to deal with a few more local outbreaks before it can declare victory. Also, so long as Ebola continues in neighboring countries the disease may be brought back to Liberia by travelers (though note this heartening item about an effective Liberian border control operation: [IOM 2/4/15]). And the risk of an unrelated jump to a human from an animal reservoir will continue indefinitely. Nevertheless, this is a moment to be savored!

Update 3/24/15: A new patient has been identified in Liberia, who probably was infected by her boyfriend, an Ebola survivor. [NYT 3/24/15]. This is disappointing, but the fact that only one instance has come to light suggests that this mode of transmission is rare.

Ongoing Transmission in Sierra Leone and Guinea

Sierra Leone initially showed a similar pattern of precipitous decline in patients, but since the end of January weekly cases have stabilized between 60 and 100. [WHO 3/4/15] This is better than exponential growth, but it’s not on track to ending the epidemic. Guinea didn’t have as sharp a peak, but it also hasn’t experienced such a dramatic improvement: about 50 cases are continuing to arise each week. In both countries the steady rate of new cases implies an Effective Reproduction Rate of about 1. Pushing this down just a little would eventually end the epidemic, while letting it rise would allow exponential growth to resume. Liberia has shown that it’s possible to snuff out the epidemic, but Sierra Leone and Guinea are not yet following in Liberia’s footsteps.

I don’t claim to know how Liberia did it, but somehow the Effective Reproduction Rate dropped to about 1 in September, then fell much lower from October on. Sierra Leone’s peak and fall were similar, but occurred about two months later, and the decline has now leveled out. While the opening of new treatment centers certainly helped in recent months, my own best guess is that the main factor in both countries is that people simply “got religion.” That is, a large enough fraction of Liberians came to accept that Ebola is caused by a virus, not a curse; that people who fall ill need to be cared for in safe settings, rather than at home; and that corpses need to be handled with extreme care. I suppose that a comparable fraction of Sierra Leone’s population reached similar conclusions, but the epidemic is now continuing there and in Guinea within sub groups that haven’t fully accepted the message.

Devilish Details

The last Ebola patient in Liberia, Beatrice Yardolo, came from a worrisome cluster of cases “in a community called St. Paul’s Bridge, located in what was one of the biggest Ebola hot spots in Monrovia, New Kru Town.” [NYT 3/6] The New York Times reported that, “[t]he outbreak was unusually violent and far-reaching, in part because it involved criminal gangs that did not cooperate with the authorities and fears that it could be spread through a knife fight with one member nicknamed Time Bomb.” Even more troubling was the fact that known contacts on several occasions left Monrovia for other parts of the country. [FrontPageAfrica 2/3/15] One of the escaped contacts died in Margibi County, and required the tracking of 256 contacts there. [GNN Liberia 2/4/15]

Ebola came into the Yardolo family from Beatrice’s cousin Steve, who probably became infected at an Ebola treatment center where he worked. [AllAfrica 3/6/15]  Steve infected several other members of the family, eventually including his daughter Amanda. Beatrice took responsibility for Amanda’s care, but again and again Amanda was mis-diagnosed and rejected from Ebola treatment centers. Beatrice was left responsible for bathing and otherwise caring for her. After Amanda died Beatrice went immediately to a treatment center started showing symptoms, which probably saved her life.

Ebola didn’t end in Liberia because people behaved well, but because the strategies of isolation and contact tracing worked despite much bad behavior and many mistakes.

Sierra Leone’s experience is vividly described in another New York Times piece. [NYT 2/18/15] The epidemic was re-ignited by three sick fishermen who landed in a poor area of Freetown in early February. Two dozen people in the area ended up contracting Ebola from this initial group before transmission was brought under control. A quarantine was imposed but was frequently broken. One shopkeeper fell ill but was afraid to go to a hospital in Freetown. Instead he broke quarantine and traveled three hours to his home village, where he visited a traditional healer, then died. He caused the infection of some 42 people in the district.

Endemic Ebola?

Ebola is still being actively transmitted in Sierra Leone and Guinea, and may yet recur in Liberia, or spread to other countries. But the Liberian experience gives every reason to hope that the techniques that worked there can eventually end this epidemic altogether. The possibility must be acknowledged, however, that the epidemic will continue indefinitely, neither growing exponentially nor definitively ending. In this case Ebola would become “endemic” to West Africa — just one of the typical diseases that people get there. I can’t disprove this — indeed it seems to be happening now in Guinea — but I have several reasons for doubting that this will happen with the current strain of Ebola:

  • It’s too deadly. A cluster of a less lethal disease might go relatively unnoticed, but this can’t happen with Ebola. The deaths of family and friends, one after another, cannot be ignored. The presence of Ebola in a community will not be tolerated for long.
  • Its incubation period is too short. A disease that takes months or years to emerge (e.g. AIDS, leprosy, tuberculosis) can hide in a human population, but Ebola emerges quickly, or not at all.
  • It’s only transmitted from person to person. Aside from the wild animal reservoir (discussed below) Ebola appears to be transmitted only from person to person. A disease that could also infect some more familiar animal, like fleas or rats, could hide in the animal reservoir and reemerge unpredictably. Fortunately, Ebola shows no sign of doing this.
  • It’s only transmitted by direct contact. Fortunately, Ebola isn’t airborne; it’s transmitted only by direct contact with bodily fluids or contaminated surfaces. This makes contact tracing and isolation so effective. It’s much more difficult to contain a disease like the flu that spreads through the air.
  • People are infectious only when they are ill.  Update 3/24/15: (except for the semen of male survivors). There is no indication that there are “Typhoid Marys” who can transmit Ebola without themselves falling ill, except for one instance in which a male survivor appears to have infected his partner, presumably through semen, which is known to contain Ebola virus for several months after recovery. [NYT 3/24/15] This will make the disease a bit more difficult to eradicate, but is not cause for panic. As noted above, the fact that just one infection of this type has come to light suggests that this mode of transmission is infrequent. Additionally, now that an example exists one might expect many “discordant couples” (in which the male is a survivor and the female is not) to use condoms, which should further reduce the risk. One question that calls for further research is how long the virus can persist in the semen of a male survivor, and whether a negative semen test is sufficient to make unprotected intercourse safe for the survivor’s partners.

For these reasons I think it’s highly unlikely that Ebola will become endemic based on human-to-human transmission (absent mutation). So long as we don’t lose focus I expect that Sierra Leone, and eventually Guinea, will be able to end this epidemic using the standard techniques of contact tracing, isolation, funeral management and education.

The Wild Animal Reservoir

In one important respect Ebola already is endemic to East Africa: For forty years it has jumped every few years from its wild animal reservoir (probably fruit bats) into a human population. Just this year an unrelated Ebola outbreak in a rural area of Uganda flared briefly and was extinguished. [CDC]  There is every reason to expect this pattern to continue, since:

  1. even when we have a vaccine it will never be feasible to vaccinate the entire relevant population,
  2. contact with infected animals such as bush meat may be reduced through education but can’t be prevented altogether, and
  3. there is no conceivable way to eliminate Ebola from the animal reservoir.

This is too bad, but it’s a bearable situation, since most outbreaks start in remote rural areas, where they can be quickly snuffed out so long as they are detected early and the response is competent and decisive.

So far as we know the West African epidemic arose from a single jump between a wild animal reservoir and a human. There might be some reason why this was an isolated incident that won’t recur. But it seems much more likely that Ebola is now established in a West African animal reservoir, from which it will now jump periodically into humans, the same way it has for decades in East Africa. After the current epidemic is brought under control it will be essential for all West African countries to establish systems for early detection of new Ebola outbreaks, as has long been the case in East Africa.

We’re lucky that infective contacts between humans and the wild animal reservoir are so rare. If Ebola became established in an animal population that lived in closer contact with humans — rats, pigs, or even dogs — animal-human transmissions could be much more frequent. There is no evidence, however, that this is happening. Genetic evidence continues to indicate that the entire West African epidemic was sparked by a single animal-human transmission in Guinea, from a bat to a 2-year-old boy.

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Yet again, Ebola has infected a caregiver: a nurse who gave extensive care to Thomas Duncan in Dallas. She wore full protective gear and is not aware of any breach of anti-infection protocol. [NYT 10/13/14] This is worrisome, but consistent with the pattern we have previously noted: How Contagious is Ebola?

Update 10/15/14: Another nurse has been diagnosed. This is tragic, and unnecessary, but completely predictable given the criminally shambolic conditions under which Duncan was treated. [AP / Mashable 10/15/14]  Obviously, America has to do a lot better. But there’s every reason to think that we will rise to the occasion. What cannot continue is for Ebola patients — especially in the last stage of the illness — to be treated casually or on an ad hoc basis. Ebola will bite you if you don’t respect it! But MSF knows how to handle Ebola patients with minimal risk to caregivers. CDC simply needs to take the lessons of Africa and Spain and Dallas to heart. The solution is simple:

  1. All healthcare providers must be trained to identify and isolate potential Ebola patients, with minimal risk to themselves and others, and
  2. Confirmed Ebola patients must be treated by fully-trained professionals, with top-notch equipment, in well-designed facilities, following clear and prudent protocols.  At the moment there are plenty of beds in the four bio-containment hospitals but at least one hospital should gear up in each major city to be able to safely treat Ebola patients. Full bio-containment isn’t necessary for Ebola.

Some facts about Ebola are becoming clear:

  • Those at greatest risk are caregivers — either healthcare providers or those who care for a seriously ill patient in the home. Intense focus and attention to detail are needed to protect a caregiver, especially when a patient is in the last stage of the illness.
    • The African protocol developed by Médecins Sans Frontières / Doctors Without Borders (“MSF”) has been extraordinarily successful, although some members of their staff have nevertheless been infected.
    • The protocols used in Spain and in the U.S., as implemented so far, have not given caregivers complete protection.
  • Patients are most infectious in the last stage of the disease. There is no evidence of transmission before a person becomes symptomatic, and even after symptoms begin patients seem to be remarkably non-contagious until the final stage. The main focus should be on where patients are, and who has contact with them, in the final stage of the illness.
  • Corpses are also highly infectious. African customs of washing and touching corpses present a second important channel of infection, that needs to be discouraged. Developed countries should not encounter this issue, however, so long as suitable precautions are taken.

These lead to a few specific conclusions:

  • In the developed world the main risk presented by Ebola is to healthcare providers. There are plenty of beds, and nobody is going to try to care for an extremely ill patient in their home. CDC needs to refine its anti-infection protocol and to provide better training and support to hospitals and staff who treat Ebola patients, and similar steps need to be taken in other developed countries. There’s every reason to think that this will happen, and indeed is already happening. Ebola will teach us, as I’m sure it taught MSF in the early outbreaks, what we need to do to stop it. I still see no reason — apart from possible mutation — why the developed world should have any problem snuffing out little Ebola outbreaks as they inevitably occur.  (I’m still quite concerned about the ability of other poor countries, with crowded slums, to do the same.)

    • Healthcare providers need to be monitored for 21 days after their last contact with an Ebola patient. Duh!
  • West African healthcare providers also need to be better protected, ideally with identical gear and an identical protocol to those in the developed world.
  • In West Africa the key to stopping Ebola is isolation beds for patients in the last stage of illness. The best feasible standard of care should be provided for humanitarian reasons, but from the perspective of stopping the epidemic the critical element is isolation. The only way to bring the Effective Reproduction Number down below one is to break the cycle of transmission to home caregivers, by isolating patients and caring for them under the anti-infection protocol. Again, this issue has been identified and is being dealt with. The big question is whether beds can be provided fast enough to get ahead of the epidemic.
  • West African funeral practices also need to be addressed, and of course corpses must continue to be buried or cremated, which may prove problematic if the numbers of deaths mount as currently predicted. [NYT 10/14/14]

It’s relatively easy to think of ways in which things could go wrong, especially when dealing with a deadly disease like Ebola. I’m not optimistic about the likely course of events in West Africa, as you might gather from previous posts. But in this post I want to make an honest effort to envision what success would look like, then work backwards to see how it might be possible to get there from here. What follows is fantasy, but with a serious purpose.

Victory Over Ebola!

It has been 42 days and there have been no new cases in any of the countries affected by the West African epidemic! The last patient has either recovered or, sadly, died. Temporary facilities have been disassembled or burned, and hospital buildings thoroughly disinfected. Everyone has been through a harrowing experience but generous aid and technical assistance from around the world should help the affected countries get back on their feet.

Animal reservoirs of Ebola still exist; it would be wonderful to extinguish the virus worldwide but it’s really hard to imagine that. Ongoing efforts will be needed to discourage contact with infected animals, such as bush meat and fruit that may have been partially eaten by infected bats. Vaccination may reduce the risk of future outbreaks, although it will be difficult to maintain universal immunity in still-poor countries, and a vaccine might not confer immunity against a new strain. So as long as Ebola exists in the wild there will continue to be occasional rural outbreaks. The world obviously must never again let Ebola get out of control!

Mopping Up

The “Effective Reproduction Rate” (Re) [Discussed in The Ebola Chain Reaction] was held down below one, month after month. That is, each person who came down with Ebola infected on average less than one other susceptible person. This was true not only in the aggregate but also in each country and region and neighborhood. The number of patients being cared for peaked, then began a slow but consistent decline, as the number of new patients each day was fewer than the day before. American troops were drawn down, then withdrawn completely, as there was no more need for additional beds.

Winning the War

Gradually, Re was forced lower and lower, down below one and then well below. How was this accomplished? Some combination of these factors:

  1. There were enough Ebola isolation beds for everyone who came down with the disease, in all affected countries, and the public had so much confidence in the care in those facilities that just about everyone who came down with Ebola was admitted to one before other family members were infected. Treatment measures and drugs like ZMapp improved the survival rate somewhat; this reduced suffering and contributed to confidence but didn’t otherwise help bring the epidemic to a stop.
  2. An Ebola vaccine, though not available in sufficient quantities to immunize everyone, was strategically given to American soldiers, healthcare providers and others who were likely to be exposed. Except for President Ellen Johnson Sirleaf and her husband the vaccine was not given out based on money or position.
  3. Infection of healthcare providers was almost completely stopped by:
    1. Universal availability of infection control gear.
    2. Comprehensive training of staff at all healthcare facilities.
    3. Procedures to minimize exposure of unprotected staff during admission or when an admitted patient begins showing Ebola symptoms.
    4. The Ebola vaccine, when it became available.
  4. Traditional funeral and burial practices were suspended by general consent after a massive public information campaign.
  5. People stopped breaking quarantine and/or lying about their Ebola exposure [Discussed in my first post], due to a broad consensus supported by religious and other opinion leaders.
  6. Urban modes of transmission turned out not to be significant, or were greatly reduced by changes in behaviors and other measures.

It would be great if one could imagine the final stage taking place before a vaccine is available, since that won’t be until around the end of the year at the earliest. Please comment if you think I’m too pessimistic, but I just don’t see how you get Re down below one in Liberia and Sierra Leone without a vaccine. Guinea is different, since their problem in recent weeks has been rural flare-ups due to infected citizens returning there from the other two countries. If Guinea can keep snuffing out these outbreaks — using the classic techniques of isolation, contact-tracing and monitoring —  it might be able to get its part of the epidemic under control before the vaccine arrives.

Boots on the Ground

President Obama announced his plan to send 3,000 U.S. troops to Monrovia on September 16, 2014. [CNN 9/16/14] The troops were outfitted and trained in record time and arrived in Monrovia on [wildly hopeful] October 16, 2014. At that time Monrovia needed [a wildly optimistic guess] 1,000 additional beds to accommodate all current Ebola sufferers. The troops set to work building facilities for 1,700 beds, which became ready for patients between [optimistically] November 1 and November 16. By then all the beds were needed, and new patients kept seeking treatment at an increasing rate since Re was still over one. The U.S. identified the problem early and built another 1,700 beds (and trained all necessary staff), also in record time. This time around they got ahead of the curve and Monrovia was finally able to offer isolated care to all Ebola sufferers.

This was the most difficult period of the epidemic, when cases were still growing exponentially, and civil order was progressively undermined. The arrival of Americans had a wonderful effect on the public mood, however. American know-how and money ensured the provision of reliable water, electricity, trash removal and in particular food supplies.While there were a few situations in which small mobs gathered around American installations it was never necessary for a U.S. serviceman to file a single shot, and nobody was injured.

Due to their excellent training and high discipline, only a handful of U.S. troops became infected with Ebola. Those who did fall ill were medevaced back to the U.S., where a combination of excellent care and their own fitness led to a much lower mortality rate than experienced in Africa. Political blow-back from these Ebola casualties was muted due to a national consensus that American needed to do whatever it could to help with the humanitarian crisis in Western Africa. Once the vaccine became available U.S. troops were protected against Ebola and this problem stopped.

Meanwhile, home care kits that had been sent to rural areas proved helpful in reducing Re somewhat, but the key to success in those areas was the addition of more beds, in this case provided and staffed by Médecins Sans Frontières.

The African Union played the same role in Sierra Leone as the U.S. did in Liberia, with the same happy effects. (This strains credulity. The U.S. may have to do the same thing in Sierra Leone itself, which will be exponentially harder the longer it is delayed.)

Guinea continued to experience flare-ups due to travelers from Liberia and Sierra Leone, but it was able to snuff each of them out, and prevent the disease from getting established in its cities.

And They Lived Happily Ever After

Is this a fairy tale or can it happen? There are a lot of ways in which it could fail. To mention just a few:

  • Every day counts when you’re battling an exponentially-growing problem. Any delay in any part of the process risks the numbers growing beyond anyone’s ability to manage them. Liberia may already be beyond the point of no return, but we’ll never know if we don’t try.
  • Sierra Leone is about as bad off as Liberia. Is someone else really going to step in there, or does the U.S. have to go there as well?
  • Political support for the U.S. intervention is likely to be tepid at the outset and could turn sharply against the project after there are casualties. This could force an early withdrawal even if the program seems to be working.
  • There could be a further breakdown of civic order that would make it impossible to get the situation under control.
  • Mistrust and rumor, or arrogance and privilege, could sabotage the program.

The scenario certainly could fail, but it might just work. We must hope against hope that it will succeed.

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.

Reproduction Rate

The way Ebola spreads is simple: from one person to another. There’s an African animal reservoir — probably fruit bats — from which the virus finds its way into a human being once or twice a year. But from then on the virus is transmitted only through bodily fluids, not via an animal vector such as mosquitoes or fleas. Ebola spreads by a simple chain reaction: each person it infects may infect one or more additional people, and so on. The key is how many susceptible people, on average, each infected person passes the virus on to. This is called the “Effective Reproduction Rate,” or “Re”. (Almost everyone* is initially susceptible to Ebola, but Re will drop proportionately if a substantial portion of the relevant population becomes immune, either by surviving or by receiving some future vaccine. The rate at which the virus would be transmitted in a completely susceptible population, with no immunity, is called the “Basic Reproduction Rate,” or “Ro”.)

  • If, on average, each infected person passes the virus on to just one other susceptible person (Re is one) the epidemic will continue at a steady rate, neither growing nor dying out. This is called an “endemic” disease. The total number of cases grows, but the rate at which new cases occur stays the same.
  • If Re is less than one the epidemic will die out, slowly or rapidly depending on where the number falls between one and zero.
  • If Re is more than one the epidemic will mushroom until some factor pushes that number back down below one. The rate of growth will depend on how big this number is, but the epidemic will relentlessly accelerate so long as Re is greater than one. This is “exponential” or “explosive” growth.

The only way to stop an epidemic is to push Re down below one. Of course it’s also best to get as close to zero as possible as rapidly as possible, but so long as Re is less than one the disease will eventually die out.

Forty Years of Rural Outbreaks

Ebola outbreaks have so far always started in rural areas, with the likely suspect usually being some sort of bush meat, typically bats or monkeys.

Home caregivers are very likely to be infected, so at the outset an Re of at least one is almost assured. Other family members and visitors are also at risk. This mode of transmission can be greatly reduced by caring for patients, as soon as they become infectious, in a facility that follows rigorous infection-control procedures. This approach has worked for Médecins Sans Frontières (“MSF”) in all prior outbreaks. (Lugubriously, this form of transmission may also be reduced when patients aren’t cared for by anyone, either because they are the last member of a family or because they are put out of the house when they fall ill.)

Healthcare providers are especially vulnerable, particularly in the early stage of the outbreak. The initial symptoms of Ebola are similar to those of many other less-infectious diseases, so the first wave of sufferers typically walk in to clinics or hospitals and are examined and cared for like other patients. Not only are doctors and nurses likely to become infected, but before the outbreak is recognized they may pass infection on to other patients. This is tragic, and definitely helped the current outbreak get a foothold, but it may ultimately not be an important element of Re. For one thing, MSF has shown that rigorous procedures and high-quality anti-infection suits can essentially eliminate this risk. As of a recent report, no MSF employees had become infected in the West African outbreak, though many other healthcare providers have been. For another, hospitals and clinics may be closed when they have become contaminated, and patients may stop going there for any illnesses once the risk of Ebola infection becomes known. The collapse of the health care system has many adverse effects, but the silver lining is the fact that people who don’t go to a hospital at all can’t either transmit or acquire Ebola there.

African funeral practices have played a big role in amplifying Re.

  • The body of someone who dies is traditionally hand-washed by members of the family. This almost guarantees that the washers will be infected.
  • Mourners at a traditional funeral may touch and even kiss the body. This can infect many people, who bring the virus with them when they return home. The entire outbreak in Sierra Leone, for example, has been traced to fourteen women who attended a single traditional healer’s funeral in Guinea. [NYT]
  • Finally, those who bury the body are at high risk unless infection-control procedures are used.

It is obviously essential to stop these funeral practices, since one victim can infect a huge number of other people this way. Again, MSF has been able to do this in the villages affected by previous Ebola outbreaks by working with local chiefs and explaining the situation to the villagers.

The impact of funeral practices on Re is affected by the mortality rate. In prior outbreaks up to 90% of those infected died, so almost all had the potential to infect many others through their funerals. In West Africa only about half seem to be dying, so the impact of funerals is somewhat reduced. This effect is swamped, however, by the large number of potential infections from one traditional funeral. Even though the reduced mortality rate makes funerals somewhat less important it is still essential to bring traditional funeral practices to a stop if Re is to be reduced below one.

In more than a dozen rural outbreaks over nearly forty years Re has been decisively driven below one, and the outbreak stopped, by rigorous infection control, contact-tracing and quarantine. The support of local communities was obtained by personal contact and education.

New Complications in West Africa

The West African outbreak, however, presents a very different picture. The health care systems in the affected countries had been damaged by years of civil war as well as profound poverty. This is the first time Ebola has appeared in any of these countries, so they were slow to recognize it and unfamiliar with the steps needed to contain it. Whatever the reasons, the virus was able to spread for several months before being recognized, and the consequences have been tragic.

Several new elements have complicated the relatively simple pattern of previous outbreaks:

  1. Ignorance, superstition and rumor have frustrated efforts to apply the established protocol, both in certain rural villages and in poor urban neighborhoods, notably the West Point district of Monrovia. Health care personnel have had to withdraw completely from a dozen “red villages” in Guinea where residents fear that MSF and Red Cross are causing Ebola rather than seeking to control it.[NYT] People have been hiding Ebola victims instead of letting them go into isolation wards.
  2. The uncontrolled spread of Ebola into several big cities raises the risk of additional modes of transmission, such as physical contact in taxis, buses and crowds, and contamination of shared surfaces.
  3. The number of patients has overwhelmed available isolation facilities.
  4. In several cases people who had been exposed to Ebola, or were already ill, have nevertheless chosen to travel, thus putting many others at risk. [Ebola Strategy 2014-08-31]  Some people have also lied about potential exposure to gain admission to hospitals, thus risking infection to doctors, nurses, staff and other patients.

The consequence has been that Re appears to be at least one in Guinea and Sierra Leone, and more like 1.5 in Liberia. An excellent article in Science projects a tripling to around 10,000 cases by September 24, and hundreds of thousands in subsequent months, with no end in sight so long as Re stays so high. [Science 2014-08-31].

The only way to stop the outbreak is to identify and implement a suite of feasible measures that together push and hold the Effective Reproduction Rate (Re) below one. It is of course also important as a humanitarian concern to provide the best possible care for those who fall ill, but care has no effect on the rate at which the virus spreads except to the extent that it implies reduction of potentially infective contacts.

The outbreak has naturally segmented itself to some degree, into rural and urban areas, and by country. A couple of attempts at quarantine barriers, called cordons sanitaire, have attempted to segment it further, with mixed success. (I plan to discuss this in a future post.) To the extent that segmentation works it may be possible to stop the outbreak using different suites of infection-reduction measures in different segments. In particular, relatively well-organized countries such as Nigeria and Senegal may well be able to bring their own smaller outbreaks under control using the standard protocol of contact tracing, monitoring and quarantine, even if the epidemic continues to grow uncontrollably in, say, Liberia.

Wild Cards

The current situation is bad enough without worrying about how it could get worse, but there are a few uncertainties that it’s useful to keep in mind.

Ebola is mutating rapidly,[Washington Post 2014-08-28] and it’s possible that the virus could change in ways that increase its infectiousness, especially through the air. That would be very problematic, to put it mildly.

An animal transmission vector might emerge, particularly in places where bodies are not promptly disposed of.

Sexual transmission might become significant in a promiscuous segment of the population, such as a subset of gay men. Not only could an infected person pass the virus on to multiple sexual partners, but this could also happen after recovery, since Ebola is found in the semen of recovered patients for up to seven weeks. [Who Fact Sheet]

Secondary effects of the outbreak could disrupt infection-reduction measures or even destabilize affected regions. The most immediate risk is a breakdown in food supplies, but one could also imagine breakdowns in other public services. Public disorder has broken out in several places, and this could continue or worsen. In the middle term the weak economies of the affected countries will be further damaged by disruption of internal and foreign trade. Also, the breakdown of the health care systems in these countries may facilitate epidemics of other diseases.

At the bottom of Pandora’s Box there is hope:

A safe and effective vaccine could bring the outbreaks to a fairly quick end. Indeed, this may be the only real hope of doing so.

Possible Preexisting Immunity A subsequent New York Times article raises the possibility that some portion of East Africans are already immune to Ebola. [NYT 9/5/14] The article cites a 2010 study in Gabon, which had had four Ebola outbreaks from 1994 to 2002. The study found Ebola antibodies in 15% of the population, ranging from 34% in some remote villages to 3% on the coast. The investigator speculated that many of the antibodies resulted from low-level exposures that weren’t sufficient to cause illness. This is interesting because it might afford a large pool of people who are already immune, who might be able to take on hazardous jobs with less personal risk, and who might be able to donate curative antibodies. There are several cautions, however:

  1. Immunity is to a particular strain.
  2. It’s not clear what level of antibodies is protective in humans.
  3. While an injection of antibodies might help an infected person fight off the disease it would not function like a vaccine to generate long-term immunity.
  4. Levels of exposure in Gabon, which had a long history of Ebola outbreaks, might be higher than in the countries currently affected.
  5. The epidemic is currently most worrisome in coastal cities, where antibodies would probably be lowest.
  6. Whatever preexisting immunity existed in remote villages wasn’t sufficient to keep Ebola from getting a foothold there.
  7. Sophisticated techniques are needed to test for antibodies.

More Information:
[Measuring Disease Dynamics in Populations: Characterizing the Likelihood of Control, Johns Hopkins]

[Exponential Growth and the Legend of Paal Paysam]