Tag Archives: Ebola Outbreak 2014

#Ebola UPDATE-Rate Of New Cases Rises, Note to Laurie Garrett, is there a case in South Africa?


h2>New for August 16th

I will try to keep new information and updates in the same post for a while until I have a chance to do a comprehensive re-overview of everything.

The 16 August update from WHO indicates a large uptick in the daily number of cases. Over the two days of the most recent reporting period an average of 76 cases per day have been identified as confirmed, probable, or suspect, with a total of 76 deaths over that period of time.

Good news is that the situation in Nigeria doesn’t seem to be developing. There were no new cases over the this reporting period, and one death. The last new cases in Nigeria were reported on August 6th for the period between August 2 and august 4. So over ten days without a new case in Nigeria probably means that the “outbreak” is burned out.

Meanwhile, there is another suspected/possible case in another country. This has happened a number of times, where a suspected Ebola case is identified. Hong Kong, the Philippines, the US, etc. have had these, and of all of the cases none have been shown to be Ebola except possibly one, and that is in Saudi Arabia did not work out either, the Saudi case was not Ebola. The new possible case is in South Africa.

The updated graph showing the increase in daily cases is inserted below as before.

And now, a personal note to Laurie Garrett. Laurie wrote this post, and I wanted to comment on it but the commenting system there did not work for me. (Perhaps one has to be subscriber.)


I love you work. It was your book, based on your Thesis at the Kennedy School, that got me interested in tropical diseases. Well, that and at the same time going to the tropics, running a makeshift health clinic there, and getting some of the diseases. I often point people to your earlier writing on influenza to find out about the true pre-Wakefield anti-vax movement, to see how the US handling of Swine Flu made it very difficult if not impossible to have a sensible national vaccine program that was not byzantium (which is what we have now)

But I think your article on not being scared enough about Ebola has some problems. I agree that this outbreak has not been taken seriously. I nave noted in my own writing that WHO and CDC, even, are coddling the public about some of this. I also noted, which I don’t think you did, that Ebola “in Africa” is Ebola in America already. One of my neighbors died of Ebola, and one of his relatives in Liberia did as well, and some of my other neighbors lost relatives, I’ve heard. This is because Liberians and other Africans live in communities with one foot in Africa and one foot here. Those who died of Ebola did so in West Africa, but they are still neighbors who live here part time or African-based relatives of neighbors who live here full or part time.

So yes, for many reasons, be concerned.

Here’s where I don’t agree with you.

First, while the cures and vaccines are truly not deployed as you point out, you are more negative than necessary. In fact you are hyperskeptical. A common phrase in hyperskepticism is “there is not a shred of evidence of…” Well, there is not a shred of evidence that my four year old is upstairs eating a peanut butter and jelly sandwich instead of the nice dinner I made my family, but that does not mean it is anywhere near impossible. In fact, he’s probably eating a peanut butter and jelly sandwich, though I can produce not a shred of evidence from here in my basement that he is. There is in fact good scientific reasons to think that the cures that have been brought to the brink of testing are likely to work, and Ebola is not like Malaria (not even close) or even viral cousins such as Influenza when it comes to vaccine prospects. The prospects are good, if only someone would work on them.

Next problem: No, Saudi has not Ebola. No, there have not been a number of actual, non-panic-based cases of Ebola outside of the affected area other than my neighbor and those he infected, in Nigeria.

Next:No, Nigeria does not actually seem to be having an outbreak. No new cases in ten days is good news. It may be over there.

We’ll see about South Africa.

But yes, I do agree with you on two other points. First, all of the health care molecules have moved to one corner of the proverbial room suffocating other health care efforts in the affected countries. This is a big deal. Second, yes, it really is possible despite major media and major organizations insisting it is highly unlikely for this outbreak to seed an outbreak pretty much anywhere in the world. Not that likely. But I won’t say that there is not a shred of evidence that it could happen (citing that every single case outside the zone for which confirmation was completed has not worked out). I’ll just say that we have no freakin’ clue how likely it is, but it is not zero and the consequences would be dire.

So, I don’t want to tone-troll your article. You went for breathless, and you got to breathless, and that’s probably a good choice, you have the credibility to pull it off and people need to hear much of what you said. But no, Ebola is not leaking out of the zone now, and yes, there is better hope I think for the existing (as in on the table, not deployed or even tested) cures and vaccines (and by the way, the “ethical considerations” are a red herring, that is true for all drug development, but seems only mentioned frequently with respect to Ebola).

End of rant. Again, love your work.




h2>End of August 16th update


Yesterday I made the optimistic statement that the number of new cases a day may be leveling off, as for two reporting periods in a row, representing five days, the new cases were about half of the previous reporting period, normalized to a per-day estimate.

Today’s report from WHO covers two days and indicates 128 more cases, so the number of new cases per day for the latest known period is actually higher than at any previous time during this outbreak. Pursuant to this I’ve replaced the pertinent graphic below. I was optimistic, but I also provided caveats. The caveats won.

Is the current Ebola Outbreak subsiding?

At some point, the Ebola Outbreak in West Africa has to slow down and stop. The disease is too hot to not burn itself out, and it has no human reservoir. Ebola accidentally broke into the human population earlier this year or late last year, probably once (see below), and despite the regular increase in daily reported cases over the last several weeks, the disease must at some point begin to level off.

The latest two updates from WHO indicate that the Ebola outbreak may be leveling off now, tough it is too early to be certain. The following graph shows the approximate number of new cases reported per day by WHO. This is calculated by taking the number of new cases in a report and dividing by the number of days covered by that report. A given estimate of daily new cases may be quite off for a number of reasons. First, even if there is a long term upward or downward trend, there is likely to be a lot of randomness in the data. Second, this is the number of cases reported in that time period, not the number of cases that manifest. It is likely that some cases manifest during the reporting period are not recorded yet, and cases manifest for the prior reporting period are included in the current reporting period. Over several reporting periods this would, obviously, even out, but a given number of days in a reporting period may be off by a day or so. So, these caveats mean that we should be very cautious in interpreting this graph.


Note that what appears to have been a fairly steady increase in number of cases, with about the same number of ups as downs but with the ups adding to a higher sum, since late June, has been followed by two reporting periods with decreases in numbers of new cases. Note also, however, that in late May the number of new cases per day went up fairly quickly then dropped again before a new steady rise occurred. If we use a moving average of 3 data points, which would combine sets of 2-4 days each to obtain something close to a 10 day effective moving average, the upward trend is more evident than any recent downward trend:

Screen Shot 2014-08-12 at 2.44.43 PM

The next two WHO reports may clarify this trend.

Mortality Rate Is Decreasing

The mortality rate for this outbreak continues to decrease slightly, which is probably a result of increase effectiveness of the response to the outbreak, despite all the news stories about how things seem out of control.


The current mortality rate is dropping below 55% given confirmed, probable, and suspected cases and deaths. But the rate varies across different categories. The outbreak-long rate for all cases and all deaths is currently 55%, and looking only at confirmed cases and deaths, it is 56%. The mortality rate for all previous African Ebola outbreaks, taking total reported cases and total reported deaths, is 66%.

This is the largest outbreak ever, and then some

Currently there are over 1,800 confirmed, probable, or suspected cases reported in the West African outbreak, and 1176 confirmed cases. Using just the confirmed cases, to be conservative, the present outbreak is 277% larger than the next largest outbreak, which was in 2000 in the Gulu, Masindi, and Mbarara districts of Uganda, with 425 cases. The total number of confirmed cases for the present outbreak represents about 49% of all of the prior African Ebola outbreaks combined.

Patient Zero Identified?

Patient Zero, who we assume is the person to whom the disease jumped from its usual animal reservoir, directly or indirectly, may have been a toddler in Guinea. The two year old child died in December 2013, which is quite a bit before this outbreak came on everyone’s radar screen, and after which it was fairly low level for a while.

I’ve long maintained that a likely way for Ebola to get into other species is from ground dwelling mammals, such as chimps, gorillas, or forest antelopes and duikers, ingesting or mouthing the discarded wadges of fruit previously handled by Ebola-carrying fruit bats. From such non-human animals the Ebola would then enter human populations from people butchering bush meat. In this case though, I wonder if the toddler may have been a direct recipient, picking up and mouthing fruit-bat spit covered fragments of fruit found on the ground. A parent’s worse nightmare, apocalypse style, to be sure.

The Famous Untested Drug

There has been a bit of complaining about my use of the term “drug” or “cure” for ZMapp, a drug that was developed to fight Ebola but not used until just now. Some have said it is not a drug until it is tested and deployed, and until then, it is a possible cure and not a real cure.

This is wrong. A “possible cure” is when you take an existing compound or substance, apply it to a pathogen or an affected animal model, and get a hopeful result. This possible cure can then be further developed to make, most of the time, nothing because these things generally don’t work out. Or, to make a cure. Which can then be tested.

In the case of the treatment now given to three patients (two survived one died), the cure was developed for Ebola based on some pretty solid science and prior experience with similar type cures working for similar diseases, successfully, in the past. The cure was not in “hopeful” or “possible” phase, but rather in developed but untested phase. The WHO convened an emergency panel of experts, yesterday, which decided that the cure should be used in the field under certain circumstances. So now there is an untested but developed cure for Ebola being deployed in West Africa. The WHO discussion on this is here.

Ebola Outbreak Continues, Probably Worsens, Perhaps Spreads

The WHO came out with a new report today with the latest figures on Ebola. These numbers take us to the end of July. There are two bits of bad news.

First, the number of new cases is high, as high as any prior report (but keep in mind that these reports cover uneven time periods). There are 163 new cases and 61 new deaths, bringing the total number of confirmed cases and deaths to 1009 and 574, with the total number of confirmed, probable, and suspected to 1,603 cases and 887 deaths.

Second, Nigeria is now in the mix. There was previously only one case in Nigeria, a Liberian man who contracted Ebola in Liberia and died in Nigeria. But now there are three probable new cases in Nigeria and one probable Death (none confirmed). According to WHO, of the Nigerian cases, “…one is a health-care worker and one is a Nigerian who travelled to Guinea — and a suspected case in a nurse.” I’m not sure if four cases (if confirmed) is an outbreak yet. If all the cases have quirky explanations having to do with other countries, than this not be anything new. But this could also be the beginning of the spread of the disease into Nigeria.

Here’s a graphic of the cumulative number of caeses by country (not counting Nigeria) and the total so far. These are all cases (confirmed, probable, suspected). You will notice that Sierra Leone is contributing the largest number of cases, but Liberia is contributing the strongest uptick in what seems to be an increase in rate of new cases (more on that below).


This graphic shows the number of cases over time and the number of deaths over time (totals). Note that the gap between the two is widening, suggesting a lowering of the mortality rate.


To try to get a better idea of mortality rate over time, here’s a graph of the an estimate mortality rate based on the total number of cases and the total number of deaths for each of the WHO reports (which come out every few days) over time. There is no sense in calculating a simple correlation coefficient or R-squared value for these data because each data point is based on the adjoining data point plus or minus (they are not independent) but one suspects a proper time series analysis would suggest a decrease.


Keep in mind that as the number of cases or deaths shifts along the confirmed-probable-suspected axis, the morality rate can change quite a bit. One might expect that the least certain category would have the lowest mortality rate because one is more likely to incorrectly assign a patient to having the illness than one is to attribute a death to the disease. Here’s the behavior of mortality rate across the different categories of available data. Note that the rate for “new” is probably going to be biased downwards if the rate of new cases is going up (because the number of people who have not died yet, but will, is greater than if the rate is going down); that 37% figure, therefore, is nothing to get excited about. Also keep in mind that “Total” is a combination of the other three categories. Given the vagueness of some of the data, one could say that a good estimate of mortality is 55%, but a large number of cases have been added in the last several days, so it might be better to say that the mortality rate in this outbreak is at least 55%.


It seems that the number of new cases is going up but this is hard to count. The WHO reports cover different time periods, and I’ll wager that even within that constraint the data are a bit funky given the on the ground situation. Over the large scale of time it is clear that the number of new cases is rising. This graph shows the number of new cases per month, but keep in mind that the dates of the various reports do not match the ends of the months cleanly so there is room for error her. These are all cases.


Since the rate of infection can go up or down over a matter of days, or a least, more rapidly than would be reflected in a month by month accounting, here’s the same data by half-month:


And, because that does not capture important detail here’s the data again by WHO report, keeping in mind that the length of time covered by each report varies.

Actual epidemiologists use much more sophisticated methods for analyzing this sort of data, but this should give you the idea that while the rate of new cases varies a lot from report to report, there is a general upward trend in the number of new cases.

This Ebola outbreak is not going away soon, it seems.

Other posts on Ebola:

<li><a href="http://scienceblogs.com/gregladen/2014/08/04/there-is-a-cure-for-ebola-we-have-it-we-just-dont-let-anyone-use-it/">There is a cure for Ebola, we have it, we just don’t let anyone use it.</a>

<li><a href="http://scienceblogs.com/gregladen/2014/08/04/ebola-outbreak-continues-probably-worsens-perhaps-spreads/">Ebola Outbreak Continues, Probably Worsens, Perhaps Spreads</a></li>
  • Ebola Perspective: Risks of spread to the US and elsewhere
  • <li><a href="http://scienceblogs.com/gregladen/2014/07/27/ebola-outbreak-in-west-africa-some-basic-information/">Ebola Outbreak in West Africa: Some basic information (Updated)</a></li>