Two developments in the fight against Ebola are important for everyone to be aware of:
First, there is a vaccine that has recently been repeatedly shown to be highly effective in chimpanzees and only requires human testing. Meaning, I would think, if toxicity testing is negative, all the available residents of the three countries affected should be the first recipients of the vaccine.
Second, there is a tailored antibody treatment for the Ebola virus that is effective in the ten people in whom it has been tested so far. Thus, if by chance you should volunteer to go to Liberia as an aid worker and be accepted, and should you catch the virus and get real sick, you can depend on your nation’s ambassador to arrange a flight home and the three doses of antibody that are required to cure you (he said, with a straight face).
These developments should make Ebola conquerable, assuming that the responsible authorities institute the correct policies and arrange for the supplies of the appropriate drugs, vaccines, and personal protective gear appropriate for the climate. Possibly that is an over optimistic assumption.
We should, however, take the long view with things like this. By “the long view”, I mean the view in which the survival of the individual means little in comparison to the survival of the species, which means little in comparison to the survival of life in general.
At the level of the long view, we have learned recently that the Ebola virus and the Marburg virus can be estimated to have diverged from one another on the evolutionary tree at least sixteen to twenty three million years ago. This contradicts the previously held view that the Ebola virus is only about ten thousand years old. For what it’s worth; it’s not what I would call “useful information” right now, but probably later some one will say, “Aha!”
New research has revealed that patients who survive Ebola infection have a different profile of virus load than those who succumb. The typical patient who survives Ebola infection has maximum virus load after four days of symptoms and then progressively reduces amounts of virus. The dying patient will show ever increasing virus load and ever worsening symptoms, with maximum load a hundred fold higher than that in a surviving patient.
Therefore, evaluation of the patterns of infection suggest that isolation of the sickest patients within four days of symptom onset can lead to complete interruption of transmission and end the epidemic. The patients with milder symptoms can be isolated too but it is the sickest ones who really need to be removed from the community.
Ironically, it is those who die of Ebola infection who are most often treated secretly at home and then buried surreptitiously with traditional washing and handling practices. These fatalities are the most efficient modes of epidemic spread for the Ebola virus.
Thus it behooves the government that wants to eliminate Ebola to encourage the people to bring in and surrender their sickest patients so that they can be properly isolated and buried aseptically. Perhaps one way to encourage the surrender of sick Ebola patients would be to ensure that every patient who dies is treated humanely and indentified individually so that the family has a place to lay flowers and perform traditional mourning rites.
Instead, it appears that patients are cut off from their families when they go downhill and die, and then the corpses are incinerated, making traditional ceremonies impossible. This policy in Liberia has, it is alleged, resulted in widespread surreptitious burials. If this is the case, a number of new infections should result from post mortem contamination.
Maybe it’s too difficult given the resources of the countries involved and the number of deaths, to provide individual graves for each victim. So far, we have had almost five thousand deaths in the three countries affected: Liberia, Sierra Leone, and Guinea. That’s a small cemetery in less than a year. None of these countries’ governments has more than a few cents per annum per person to spend on health care. Even the United Nations appeal for donations hasn’t been going well as yet.
Nonetheless, if careful isolation of the sickest patients is practiced, there is likely to be a quick extinction of this epidemic. It should be easy to start isolation of a very sick patient within four days of the onset of the first symptoms. Public education has been effective so far in this epidemic and this should be emphasized, especially the need to be isolated within four days to prevent others from falling ill.
On the other hand, it is clear that respiratory isolation and the quarantines that have been enforced are completely unnecessary. The nurse who has been in quarantine despite testing negative and having no symptoms is apparently going to court to get the quarantine lifted. We hope that, if a judge is forced to decide the wisdom of the quarantine order, that she will come down on the nurse’s side and award damages against the state of Maine.
According to an Associated Press report on October 24, in Liberia a policy of mandatory cremation was established in order to control the spread of Ebola through unsafe burial practices. This policy has allegedly led to abandonment of the hospital facilities in Liberia. Patient’s families are so afraid of cremation and not being able to know where their loved ones are buried that they are avoiding hospitalization and burying them secretly. As a result, Ebola treatment centers are only half full. In contrast, in the other two countries affected, cremation is not mandated, and hospitals are full.
Secret burial without everyone involved falling ill is possible in part because three out of four people infected with Ebola are asymptomatic. This means that an epidemic will certainly end before a quarter of the people become sick with Ebola. If the mortality rate is fifty percent, then at most one eighth of the population will die. In addition, it has been noted that serially transmitted virus becomes less and less virulent until it disappears after five generations.
These factors suggest that more nurses may have been infected with Ebola than just the two who became symptomatic, further impugning the isolation precautions that were taken in Dallas.
It appears on further examination that the Ebola epidemic will eventually burn itself out, but there may be major uncertainties in counting the victims, especially in Liberia.
Here is a comment from NYT that I think explains a lot, but I don’t see how it explains everything:
I remember reading, at least a decade or two ago following one of the earlier and smaller outbreaks of ebola, an article in The New Yorker magazine written by by a woman who had trained in biology but instead had previously been an anthropologist in the African area where the outbreak occurred. She was included in the medical response team that went to treat the outbreak of ebola because she knew the local language. In Africa, she did not do medical work but instead interviewed patients. She tracked the history of the outbreak from patient zero following patient to patient transmission and mortality as far as retransmission five. What she found that was that infectivity and mortality decreased with each retransmission further from patient zero. After retransmission five away from patient zero, the disease essentially vanished; i. e., the disease burned itself out. She questioned if ebola was natively a human disease or some unknown animal disease that occasionally jumped to humans through a rare mutation but then continued to mutate to weaker forms with each human retransmission until the disease outbreak vanished. I have never seen any followup on her ideas. Could such a weakening with progressive retransmission explain the reported dearth of anticipated patients?
In other words, the virus mutates to become weaker each time it crosses from one patient to the next. After going through five patients, the virus becomes inactive and no further transmissions occur. If this were true, it seems to me that the virus would have already burned out; instead, we have ten thousand known victims and five thousand deaths as of this week. On the other hand, if an index patient were responsible for numerous new patients, for a time the rates would increase rapidly. The time it takes for a complete cycle would be eight to fourteen days for incubation plus two to three weeks to succumb, at which time one is highly infectious. Altogether, three to five weeks to cycle from one patient to the next, and less than six months for five generations.
There has to be a non-human source that is starting new index cases for the epidemic to last longer than that, or to grow any longer. We still do not have definite information on a non-human vector other than possibly a bat.
There has been, for the last week or so, a diminution in the rate of new cases of Ebola virus in Liberia, while the epidemic continues to rage in the other two countries affected. There is no clear explanation as to why, whether the rate is really dropping, or bodies are being secretly disposed of, no one knows for sure. Another critic has pointed out that the prediction of a million victims by January was a worst case scenario, “if nothing was done”, so the measures that are being taken have proved effective. In any case, several new hospitals have beds still available for patients, unlike the situation a few weeks ago when patients were turned away because all the beds were full.
Another intriguing issue with Ebola virus transmission is the discovery that the conjunctiva of the eye are unusually susceptible to invasion by the virus. This makes transmission by finger contact very easy. Ebola patients, even if they are not vomiting, usually sweat profusely, and as the illness progresses, the amount of virus in the sweat increases. The corpse is highly infectious due to dried sweat on the skin.
So, if one touches a sweating Ebola patient and then rubs one’s eye, as one often does, the infection is readily transmitted. Small amounts of virus, on the order of one to ten virions, are sufficient for infection. Once infection sets in, there is much variability in symptom progression, and older patients seem to be more likely to succumb. There may also be a significant subset of the population that is naturally resistant to Ebola.
Finally, the two nurses who were infected while treating the Liberian man who died in Dallas of Ebola have both recovered and are being released from the hospital. No one has said so, but it is clear that they were infected because they were following the CDC protocol, which was inadequate until it was suddenly changed some time after they were exposed (on Sept 28, when he was admitted, until Sept 30, when the Ebola test was confirmed and isolation was much improved). Specifically, the suits they wore probably lacked goggles and overall hoods, and worst of all, had inadequate protection for the feet. Now the protocols require an overall Tyvek suit, goggles, a rubber apron, and rubber boots. However, they still do not require a chlorine spray while de-gowning, something that Doctors Without Borders does in their Ebola hospitals.
It certainly appears that no one who was on the plane with the nurse who fell ill the next morning with Ebola has gotten sick. Apparently the virus is too busy multiplying within the body before symptoms appear, thus there is not enough virus to be infectious. Whether the drop in cases in Liberia means that the Ebola epidemic is burning out, will have to wait for future trends.
There has been a great deal of hysterical response to the issue of Ebola transmission from people who are returning from African visits. A number of people who were nowhere near the three countries affected have been barred from school or work for three weeks. One victim of this hysterical quarantine has sued the school that imposed it for damages. From the available evidence, we can confidently say that there is little or no risk of getting Ebola by casual contact with a patient who is not symptomatic, that is, sweating.