The following charts are updates to previous posts about the
Ebola epidemic in West Africa.
I will update these charts as new data becomes available.
Additional resources may be found at StopEbola.uk:
I will update these charts as new data becomes available.
Additional resources may be found at StopEbola.uk:
April 29, 2015
My latest update regarding the history of the Ebola epidemic can be found here:
http://dougrobbins.blogspot.com/2015/04/ro-and-history-of-ebola-epidemic-in.html
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March 11, 2015
Data from the World Health Organization is complete through March 8.
The exponential rate of growth observed in the initial months of the epidemic was broken in mid-October, 2014. The rate of disease transmission fell from early December, 2014 to mid-January, 2015. Since that time, the rate of transmission has remained fairly constant at about 50 new cases per day. The most recent data indicates a slight increase in the rate of transmission. The geographic dispersion of new cases is also a serious concern.
The Ro history for the epidemic has been calculated, and appears at the bottom of this update. Ro represents the rate of new disease transmission, with the number representing the number of new cases generated by each case of Ebola. An Ro value greater than 1 means the epidemic is growing, and a value less than 1 means the epidemic is diminishing. Ro approached 1.3 during the period of most rapid growth, and has been approximately 0.9 while epidemic declined. A recent rise in Ro is noted, and is of some concern.
The most important chart of the Ebola epidemic is now the chart of daily new cases. Daily new cases have been falling since early December, after peaking around 160 new cases per day. New cases fell to about 50 cases per day in the second week of January. Since that time, the rate of transmission has stalled at about 50 new cases per day, with a slight uptick in the rate of transmission seen in the latest data.
The current rate of 50 new cases per day was last seen in early August, 2014. This rate of disease transmission is still a tragedy, and still dangerous. Ebola is a disease capable of explosive growth, and cannot be considered contained until it is eradicated.
The locus of disease transmission in West Africa has shifted westward, from Liberia to Sierra Leone and western Guinea. The dispersion of new cases is also a concern. In the last two weeks, new cases have appeared in four provinces of Guinea which border Senegal, Mali, and Cote d'Ivoire. Intervention efforts must remain flexible to meet the disease wherever it appears.
Sierra Leone remains the most active area of Ebola transmission.
The exponential rate of growth observed in the initial months of the epidemic was broken in mid-October, 2014. The rate of disease transmission fell from early December, 2014 to mid-January, 2015. Since that time, the rate of transmission has remained fairly constant at about 50 new cases per day. The most recent data indicates a slight increase in the rate of transmission. The geographic dispersion of new cases is also a serious concern.
The Ro history for the epidemic has been calculated, and appears at the bottom of this update. Ro represents the rate of new disease transmission, with the number representing the number of new cases generated by each case of Ebola. An Ro value greater than 1 means the epidemic is growing, and a value less than 1 means the epidemic is diminishing. Ro approached 1.3 during the period of most rapid growth, and has been approximately 0.9 while epidemic declined. A recent rise in Ro is noted, and is of some concern.
The most important chart of the Ebola epidemic is now the chart of daily new cases. Daily new cases have been falling since early December, after peaking around 160 new cases per day. New cases fell to about 50 cases per day in the second week of January. Since that time, the rate of transmission has stalled at about 50 new cases per day, with a slight uptick in the rate of transmission seen in the latest data.
The current rate of 50 new cases per day was last seen in early August, 2014. This rate of disease transmission is still a tragedy, and still dangerous. Ebola is a disease capable of explosive growth, and cannot be considered contained until it is eradicated.
The locus of disease transmission in West Africa has shifted westward, from Liberia to Sierra Leone and western Guinea. The dispersion of new cases is also a concern. In the last two weeks, new cases have appeared in four provinces of Guinea which border Senegal, Mali, and Cote d'Ivoire. Intervention efforts must remain flexible to meet the disease wherever it appears.
The chart of cumulative cases has taken on the S-shaped curve, indicating decline in the rate of transmission, but has not approached a zero rate of transmission.
Ro is the parameter which indicates the rate of transmission for an epidemic. The number Ro indicates the number of subsequent new cases, on average, generated by each case. Thus, an Ro value larger than 1 indicates a growing epidemic; an Ro value less than one indicates the epidemic is shrinking.
I applied a 3rd-degree polynomial regression to three parts of the cumulative case chart. (The entire case history was too complicated to represent well with a single expression, and contains some large data revisions in the middle of the epidemic.) I used the regressions to smooth the data, and calculate the daily new cases, and the rate of Ebola transmission, assuming an average 8-day lag between infections.
From these regressions, I calculated Ro for the history of the epidemic.
The epidemic grew quite rapidly during the period when Ro exceeded 1.2, in part due to the extremely rapid course of the disease. Ro fell below 1 in late September, and the growth of the epidemic declined substantially. New cases in Liberia are approaching zero, but the main locus of transmission has shifted westward, into Sierra Leone. In the fall of 2014, the World Health Organization set a goal of placing 70 percent of patients in isolation, after which WHO anticipated ending the epidemic by January 2015. Clearly, the desired level of disease transmission was not achieved, and the epidemic did not end.
Ro approached 0.9, at its lowest point. While the number of new cases is still declining, Ro has begun rising again, which is a matter of serious concern.
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My previous posts on the Ebola topic can be viewed here:
Previous
Posts
Discusses the exponential rate of growth of the epidemic, and likely
future changes to the pathogen.
Discusses the inadequacy of the medical response in terms of a linear
response to an exponentially growing problem.
Discusses the geographic distribution of populations corresponding to
points on the exponential extrapolation.
References
http://www.who.int/csr/disease/ebola/situation-reports/en/
Infighting among health authorities fighting the Ebola epidemic.
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Obsolete Updates
February 13, 2015
Data from the World Health Organization is complete through February 8.
The exponential rate of growth observed in the initial months of the epidemic was broken in mid-October, 2014. The rate of disease transmission fell from early December, 2014 to mid-January, 2015. Since that time, the rate of transmission has remained fairly constant at about 50 new cases per day. The most recent data indicates a slight increase in the rate of transmission. The geographic dispersion of new cases is also a serious concern.
The most important chart of the Ebola epidemic is now the chart of daily new cases. Daily new cases have been falling since early December, after peaking around 160 new cases per day. New cases fell to about 50 cases per day in the second week of January. Since that time, the rate of transmission has stalled at about 50 new cases per day, with a slight uptick in the rate of transmission seen in the latest data.
The current rate of 50 new cases per day was last seen in early August, 2014. This rate of disease transmission is still a tragedy, and still dangerous. Ebola is a disease capable of explosive growth, and cannot be considered contained until it is eradicated.
The locus of disease transmission in West Africa has shifted westward, from Liberia to Sierra Leone and western Guinea. The dispersion of new cases is also a concern. In the last two weeks, new cases have appeared in four provinces of Guinea which border Senegal, Mali, and Cote d'Ivoire. Intervention efforts must remain flexible to meet the disease wherever it appears.
January 15, 2015
Data from the World Health Organization is complete through February 1. Case numbers from Liberia continue to lag data from Sierra Leone and Guinea.
The exponential rate of growth observed in the initial months of the epidemic was broken in mid-October, 2014. The rate of disease transmission has been falling since early December, 2014.
The most important chart of the Ebola epidemic is now the chart of daily new cases. Daily new cases have been falling since early December, after peaking around 160 new cases per day. New cases fell to about 100 cases per day in early January, and are now trending downward at about 50 new cases per day.
The current rate of 50 new cases per day was last seen in early August, 2014. This rate of disease transmission is still a tragedy, and still dangerous. The locus of disease transmission in West Africa has shifted westward, from Liberia to Sierra Leone and western Guinea. Intervention efforts must remain flexible to meet the disease wherever it appears.
December 24, 2014
Data from the World Health Organization is complete through December 20. Case numbers from Liberia continue to lag data from Sierra Leone and Guinea.
The exponential rate of growth observed in the initial months of the epidemic was broken in mid-October, 2014. If the original rate of growth had continued, cumulative cases would number about 45,000, rather than the current figure of 19,400. A tragic number of new cases are still occurring. Over 100 people are still falling ill with Ebola every day.
The rate of daily new cases is falling, but erratically. The number of daily new cases is persistently high, and not far below the peak number of cases seen in October and November.
December 1, 2014
Data released on December 1 2014 by the World Health Organization shows that the epidemic set a new record in the number of daily new cases, exceeding 200 new cases per day. The interpolated and smoothed chart below also shows a new record of 161 new cases per day.
The daily number of new cases had been declining from early November through November 17, raising hopes that the epidemic was coming under control. However, the latest case numbers from Liberia and Sierra Leone have sharply reversed that trend. These numbers are insufficient to draw clear conclusions, as we have only a few data points. But the reversal of the declining trend and the new record of daily new cases are extremely troubling.
As progress is made against the epidemic, the most dangerous opponent may be complacency.
November 29, 2014
The growth rate of reported Ebola cases has stabilized when considering the entire epidemic. There has been a sharp reduction in the rate of transmission in Liberia. However, gains in Liberia are offset by a continuing high rate of transmission in Sierra Leone, as seen in the following charts of cumulative cases by country, on linear and logarithmic scales. The epidemic continues to grow at a nearly exponential rate in Sierra Leone, with only slight improvement noted in the past two weeks.
The Ebola Response Roadmap issued by the World Health Organization on August 28, acknowledged that the aggregate case load could exceed 20,000 cases, which I considered unrealistically optimistic at the time. The reduction in the rate of growth to date, remarkably, appears to meet the projections of the WHO roadmap. It is a credit to the all of the organizations working to end the epidemic to see the progress made to date. But the job is not complete, and the situation remains dangerous, as long as the disease continues to spread in Sierra Leone, or any other locality.
Six cases have now been reported in Mali, which borders Guinea to the north. Contacts from these cases are being traces. Still new infections in Mali represent a troubling extension of the disease into the interior of Africa, and outside the countries with intensive efforts to quell the epidemic.
Like firefighters working to control a wildfire, efforts to quell the epidemic must continue unabated as long a sparks remain. The official number of daily new cases is now about 150, down from 170 about two weeks ago. There is good reason to be hopeful, but the fire is still burning.
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The following chart is the number of reported daily new cases of Ebola, interpolated and smoothed with a nine-day rolling average. The exponential rate of growth was broken in mid-September. Recent data is distorted by data revisions, but appears to have settled around 150 new cases per day. There are hopeful signs of a decline in new cases over the past two weeks, but there are still great doubts about the accuracy of the official case numbers. Dr. Hans Rosling, epidemiologist acting as consultant to Liberia's Health Ministry, stated on November 5, "We are absolutely sure that we cannot be sure about the data."
Death rates calculated from reported cases continue to fall. While a decline in death rates is expected, the magnitude of decline seems improbable. WHO also reports substantial under-reporting of Ebola deaths. This should be of concern to health authorities, because it means that many burials are not being conducted according to safety protocols.
November 14, 2014
Infighting among health authorities fighting the Ebola epidemic.
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Obsolete Updates
February 13, 2015
Data from the World Health Organization is complete through February 8.
The exponential rate of growth observed in the initial months of the epidemic was broken in mid-October, 2014. The rate of disease transmission fell from early December, 2014 to mid-January, 2015. Since that time, the rate of transmission has remained fairly constant at about 50 new cases per day. The most recent data indicates a slight increase in the rate of transmission. The geographic dispersion of new cases is also a serious concern.
The most important chart of the Ebola epidemic is now the chart of daily new cases. Daily new cases have been falling since early December, after peaking around 160 new cases per day. New cases fell to about 50 cases per day in the second week of January. Since that time, the rate of transmission has stalled at about 50 new cases per day, with a slight uptick in the rate of transmission seen in the latest data.
The current rate of 50 new cases per day was last seen in early August, 2014. This rate of disease transmission is still a tragedy, and still dangerous. Ebola is a disease capable of explosive growth, and cannot be considered contained until it is eradicated.
The locus of disease transmission in West Africa has shifted westward, from Liberia to Sierra Leone and western Guinea. The dispersion of new cases is also a concern. In the last two weeks, new cases have appeared in four provinces of Guinea which border Senegal, Mali, and Cote d'Ivoire. Intervention efforts must remain flexible to meet the disease wherever it appears.
The following charts are updates to the original extrapolations made on this blog in early August.
The Ebola Response Roadmap issued by the World Health Organization on August 28, acknowledged that the aggregate case load could exceed 20,000 cases, which I considered unrealistically optimistic at the time. The reduction in the rate of growth to date, remarkably, appears to meet the projections of the WHO roadmap. It is a credit to the all of the organizations working to end the epidemic to see the progress made to date. But the job is not complete, and the situation remains dangerous, as long as the disease continues to spread in Sierra Leone, or any other locality.Data from the World Health Organization is complete through February 1. Case numbers from Liberia continue to lag data from Sierra Leone and Guinea.
The exponential rate of growth observed in the initial months of the epidemic was broken in mid-October, 2014. The rate of disease transmission has been falling since early December, 2014.
The most important chart of the Ebola epidemic is now the chart of daily new cases. Daily new cases have been falling since early December, after peaking around 160 new cases per day. New cases fell to about 100 cases per day in early January, and are now trending downward at about 50 new cases per day.
The current rate of 50 new cases per day was last seen in early August, 2014. This rate of disease transmission is still a tragedy, and still dangerous. The locus of disease transmission in West Africa has shifted westward, from Liberia to Sierra Leone and western Guinea. Intervention efforts must remain flexible to meet the disease wherever it appears.
December 24, 2014
Data from the World Health Organization is complete through December 20. Case numbers from Liberia continue to lag data from Sierra Leone and Guinea.
The exponential rate of growth observed in the initial months of the epidemic was broken in mid-October, 2014. If the original rate of growth had continued, cumulative cases would number about 45,000, rather than the current figure of 19,400. A tragic number of new cases are still occurring. Over 100 people are still falling ill with Ebola every day.
The rate of daily new cases is falling, but erratically. The number of daily new cases is persistently high, and not far below the peak number of cases seen in October and November.
December 1, 2014
Data released on December 1 2014 by the World Health Organization shows that the epidemic set a new record in the number of daily new cases, exceeding 200 new cases per day. The interpolated and smoothed chart below also shows a new record of 161 new cases per day.
The daily number of new cases had been declining from early November through November 17, raising hopes that the epidemic was coming under control. However, the latest case numbers from Liberia and Sierra Leone have sharply reversed that trend. These numbers are insufficient to draw clear conclusions, as we have only a few data points. But the reversal of the declining trend and the new record of daily new cases are extremely troubling.
As progress is made against the epidemic, the most dangerous opponent may be complacency.
November 29, 2014
The growth rate of reported Ebola cases has stabilized when considering the entire epidemic. There has been a sharp reduction in the rate of transmission in Liberia. However, gains in Liberia are offset by a continuing high rate of transmission in Sierra Leone, as seen in the following charts of cumulative cases by country, on linear and logarithmic scales. The epidemic continues to grow at a nearly exponential rate in Sierra Leone, with only slight improvement noted in the past two weeks.
The following charts are updates to the original extrapolations made on this blog in early August.
November 21, 2014
Figures from the World Health Organization show a continuing trend of improvement in the cumulative number of Ebola Cases. Rates of transmission are falling in Guinea and Liberia, although the daily number of new cases is still rising in Sierra Leone. The falling rate of transmission in Liberia indicates success in educating the public about the disease and implementing basic public health measures. At this time, only 18 of 53 planned Ebola treatment centers are open. The epidemic is diminishing due to success in changing behaviors which contributed to the spread of the disease.
Six cases have now been reported in Mali, which borders Guinea to the north. Contacts from these cases are being traces. Still new infections in Mali represent a troubling extension of the disease into the interior of Africa, and outside the countries with intensive efforts to quell the epidemic.
Like firefighters working to control a wildfire, efforts to quell the epidemic must continue unabated as long a sparks remain. The official number of daily new cases is now about 150, down from 170 about two weeks ago. There is good reason to be hopeful, but the fire is still burning.
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The following chart is the number of reported daily new cases of Ebola, interpolated and smoothed with a nine-day rolling average. The exponential rate of growth was broken in mid-September. Recent data is distorted by data revisions, but appears to have settled around 150 new cases per day. There are hopeful signs of a decline in new cases over the past two weeks, but there are still great doubts about the accuracy of the official case numbers. Dr. Hans Rosling, epidemiologist acting as consultant to Liberia's Health Ministry, stated on November 5, "We are absolutely sure that we cannot be sure about the data."
Death rates calculated from reported cases continue to fall. While a decline in death rates is expected, the magnitude of decline seems improbable. WHO also reports substantial under-reporting of Ebola deaths. This should be of concern to health authorities, because it means that many burials are not being conducted according to safety protocols.
November 14, 2014
The latest figures from the World Health Organization show a continuing trend of improvement in the cumulative number of Ebola Cases. Rates of transmission are falling in Guinea and Liberia, although the number of cases is now rising sharply in Sierra Leone. The falling rate of transmission in Liberia indicates success in educating the public about the disease and implementing basic public health measures. At this time, only 17 of 53 planned Ebola treatment centers are open. The epidemic is diminishing due to success in changing behaviors which contributed to the spread of the disease.
Four cases have been reported in Mali, which borders Guinea to the north. The three new cases are unrelated to the previously reported case, and represent a troubling extension of the disease into the interior of Africa, and outside the countries with intensive efforts to quell the epidemic.
Like firefighters working to control a wildfire, efforts to quell the epidemic must continue unabated as long a sparks remain. The epidemic is still growing at a rate of about 160 new cases a day. By comparison, in July of this year, the rate of transmission was about 20 cases a day. The world was unable to control the epidemic at that level.
There is good reason to be hopeful, but the fire is still burning.
Four cases have been reported in Mali, which borders Guinea to the north. The three new cases are unrelated to the previously reported case, and represent a troubling extension of the disease into the interior of Africa, and outside the countries with intensive efforts to quell the epidemic.
Like firefighters working to control a wildfire, efforts to quell the epidemic must continue unabated as long a sparks remain. The epidemic is still growing at a rate of about 160 new cases a day. By comparison, in July of this year, the rate of transmission was about 20 cases a day. The world was unable to control the epidemic at that level.
There is good reason to be hopeful, but the fire is still burning.
November 7, 2014
There are definite indications that the Ebola epidemic in Liberia is easing. Anecdotal reports indicate there are beds available in treatment centers, and burial teams are collecting fewer bodies from the city. Official numbers are unfortunately still highly questionable, with recent changes dominated by revisions, rather than by new cases. Following a large upward revision on October 25, there has been an almost unbelievably low of number of reported new cases. Recent case numbers in Sierra
Leone are also dominated by revisions to previous estimates, but large numbers of new cases are still being reported.
Avoidance of official treatment centers is still a problem, due to fear and cultural objections to the approved safe burial practices and/or cremation.
The following charts were prepared from case numbers issued by the World Health Organizations. Case numbers are subject to study and subsequent revision. Reporting from the affected countries has been somewhat erratic, and at irregular intervals. I interpolated the cumulative number of cases in certain countries to obtain discrete reporting dates for the entire epidemic.
The exponential extrapolation is the original extrapolation, created by an exponential regression to the data from May 23 to August 26, with days beginning on May 23. Despite the recent positive reports from West Africa, data continues to fall near the line of the original extrapolation.
