March of Ebola: in numbers

The Ebola virus epidemic in west Africa presents a complex picture in early fall, 2014. Guinea, Liberia and Sierra Leone remain in crisis. There is also a smaller epidemic in Democratic Republic of Congo, and several cases have been reported in Nigeria and Senegal. A few cases were imported into the U.S. and Europe, and the disease has been transmitted to health-care workers there.

The World Health Organization (WHO), an arm of the United Nations based in Geneva, published most of the data available. It has offices in all the countries and operates longstanding efforts to report and combat chronic and epidemic diseases. The U.S. Centers for Disease Control and Prevention (CDC), based in Atlanta, has been issuing reports trying to estimate trends in WHO data but has only a little information of its own.

Through late summer, WHO published data about the 2014 west Africa outbreak of Ebola virus via its Global Alert and Response (GAR) reports. This year GAR also described outbreaks of avian flu, MERS and polio and announced a recent outbreak in Uganda of Marburg–a virus closely related to Ebola. At the end of August, WHO began a series of Situation Reports focused on the 2014 Ebola crisis countries.

Chart of case counts: The development of Ebola in the 2014 crisis countries of west Africa can be most clearly described with a semilogarithmic chart, an ordinary tool for research scientists.


Source: World Health Organization, United Nations

The chart shows total Ebola cases reported, by day of 2014, for the three countries in crisis. Counts of cases are measured through base-2 logarithms. An increase of one unit in a base-2 logarithm represents doubling of a count. The number of days for such an increase is the doubling time. When a logarithmic series of total cases climbs steadily, an outbreak is uncontrolled. When a trend levels, an outbreak is usually being controlled.

Reports from west Africa began late, only after at least 50 to 80 cases per country had accumulated. It looks likely that the first cases occurred several months before the first WHO reports. According to CDC, the first confirmed case from the current epidemic can be traced to Guinea, in December, 2013.

Crisis countries: Guinea reported Ebola cases first, on March 22. It acted with some success to control the outbreak through isolation of victims in care centers and supportive treatments. However, as the blue-colored series in the chart shows, Guinea has suffered successive waves of Ebola virus disease. In early August, a new wave began in and near Conakry, the capital, which has yet to be controlled.

Sierra Leone began to report Ebola cases June 1. Extending the case-count trend back to logarithm zero–that is, to one case–suggests the epidemic there really started in early February. Sierra Leone has been less successful than Guinea with control efforts. The green-colored series indicates a shorter doubling time.

Liberia began to report Ebola cases June 16. Extending its case-count trend suggests the epidemic there really started in early April. Liberia has shown the least success controlling the epidemic. Through July and August, the magenta-colored series indicated a doubling time of less than 20 days.

Trends: Since August, the trend in Liberia from WHO reports looks to have leveled, but its crisis is not really being addressed, and those reports acknowledge that current data are not reliable. Instead, Liberia’s health-care and reporting resources have failed. In early August, news reports showed dead Ebola victims lying in streets. In early September, Liberia’s government admitted victims were being turned away from care centers, after that had been reported for weeks.

The trend line for Liberia from July and August predicts more than ten thousand Ebola cases by now, while the latest WHO report shows a little over four thousand. So far, trends indicate no crisis country has brought the epidemic under control. The three differ in rates of increase: the most unfavorable is Liberia, with a doubling time probably still less than 20 days; the least unfavorable is Guinea, with a doubling time around 45 days.

Responses: So far, only the United States government has begun substantial assistance. President Obama requested and Congress approved over $1 billion in assistance, using funds already appropriated. At last report, the U.S. Army had over 500 troops in Liberia of about 4,000 committed, was training more for service at a rate of about 500 per week and had committed equipment and materials to build and supply 17 treatment centers there.

Other significant international efforts as of mid-October:
France, Guinea, about $100 million appropriated, one treatment center being built
Britain, Sierra Leone, no funds yet appropriated, one treatment center being built
Germany, no presence, about $130 million appropriated, airlifts operating via Senegal
• Cuba, Sierra Leone, about 160 health-care workers, about 300 more preparing for Liberia and Guinea
• Russia, no presence, no funds appropriated, one mobile test laboratory supplied

– Craig Bolon, October 19, 2014

Ebola response, Situation Report 8 Update, World Health Organization, October 17, 2014

Ebola response, Situation Report 8, World Health Organization, October 15, 2014

Sarah Boseley, World Health Organization admits botching response to Ebola outbreak, Manchester Guardian (UK), October 17, 2014

Felicia Schwartz, U.S. military effort to combat Ebola in Africa to enter new stage, Wall Street Journal, October 15, 2014

Craig Bolon, Ebola: health-care crisis in west Africa, Brookline Beacon, September 15, 2014

Note: Staff of the World Health Organization gathered and published data referenced for this article, but apparently they did not chart their data, or they ignored what a chart should have shown.

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