09/16/2014 05:00 EDT | Updated 11/15/2014 05:59 EST

Ebola outbreak by the numbers

U.S. President Barack Obama is announcing a "ramping up" of medical assistance to the West African countries now in the throes of a worsening Ebola epidemic.

White House press secretary Josh Earnest said Obama will announce details about the additional medical aid during a visit today to the Centres for Disease Control and Prevention (CDC) in Atlanta.

Obama has called the Ebola outbreak a national security priority.

The number of cases and the numbers of deaths in the current outbreak already exceed the totals for all previous outbreaks combined.

The current outbreak in West Africa is thought to have started in December. A separate outbreak began in the Democratic Republic of Congo in August.

The first known Ebola outbreaks took place in 1976.

Here's a look at Ebola by the numbers.

Ebola outbreak in West Africa spreading rapidly

Number of countries with cases: 5 (Guinea, Liberia, Sierra Leone, Nigeria, Senegal)

Number of cases as of Sept. 12: 4,784

Number of deaths as of Sept. 12: 2,400

The World Health Organization has yet to release a report with the above numbers, which were provided by WHO director general Margaret Chan at a media conference on Friday in Geneva. Chan noted that her numbers could be an underestimate. The latest report by WHO provides the numbers as of Sept. 7.

Number of new cases, Sept. 7-12: 394

Number of deaths, Sept. 7-12: 174

Of the 4,390 cases (confirmed, probable or suspected) as of Sept. 7, almost half — 48 per cent — had been reported in the previous 21 days, a clear indication the disease had been spreading rapidly.

The disease is spreading most rapidly in Liberia, "driven by a surge of cases in the capital, Monrovia," the WHO says.

On a positive note, four districts in Guinea, three in Sierra Leone, and one in Liberia reported no new cases during the 21 days ending Sept. 7. However, one area in Liberia and one in Guinea had been Ebola-free but reported their first cases during the week ending Sept. 7.

Number of deaths as a share of the number of total cases, West Africa: 51 per cent

Ebola takes down health-care workers

Number of cases involving health-care workers in Guinea, Liberia, and Sierra Leone, as of Sept. 7: 301

Number of deaths. among those cases: 144 (48 per cent)

Number of health professionals Cuba is sending to Sierra Leone for Ebola response: 165 (The Cubans are set to arrive in the first week of October and stay six months.)

Number of doctors and nurses needed for a 70- to 80-bed Ebola treatment centre: 200

Number of beds available to treat an Ebola patient anywhere in Liberia: 0 (Th humanitarian response to the epidemic is running short on almost everything from body bags to mobile laboratories.)

Percentage of health-care workers that the WHO wants to be from foreign countries: 20

How one person spread the Ebola virus in Nigeria

The Ebola numbers for Nigeria show how the virus spreads, because all 21 cases, which include eight deaths, are believed to have followed a transmission chain that began when Liberian government official Patrick Sawyer travelled from Liberia to Lagos, Nigeria on July 20.

Number of people monitored in Lagos: 353

One man who evaded the monitoring travelled to Port Harcourt. That man later recovered but the doctor who treated him died of Ebola.

Number of people monitored in Port Harcourt: 451

Senegal has reported one case of Ebola, a person who travelled there from Guinea on Aug. 20. That led to the monitoring of 67 people twice daily. None had tested positive as of Sept. 7. The initial case has now fully recovered.

The other Ebola outbreak: Democratic Republic of Congo

Number of cases in DRC, as of Sept. 9: 62

Number of new cases, Sept. 3-9: 31

Number of deaths, as of Sept. 9: 35

The WHO says all the cases are linked to an initial case reported to the WHO on Aug. 26. This outbreak is not connected to the one in West Africa.

The U. S. response

Amount the U.S. government has spent so far: more than $100 million US (Ned Price, National Security Council)

Amount the U.S. Agency for International Development announced last week it would spend to provide 1,000 treatment beds in Liberia and 130,000 protective suits for health workers: up to $75 million US

Additional amount the Obama administration is asking Congress to provide for sending additional supplies and public health experts, and to develop potential Ebola medications and vaccines: $88 million US

Number of CDC staffers in West Africa working on outbreak control: 103 (The CDC plans to send about 50 more.)

Number of Americans evacuated to U.S. hospitals from West Africa during this outbreak: 4 (Three at Emory University Hospital in Atlanta and one at the Nebraska Medical Center in Omaha.)

Disease projections

Total number of cases predicted by the WHO: 20,000 (WHO hopes to control the outbreak within nine months.)

Midas* projection of the number of cases through Oct. 12:

- If control of the epidemic stays about the same: 18,406

- If control improves: 7,861

- If control worsens: 54,895

(*Midas, Models of Infectious Disease Agent Study, is sponsored by the U.S. National Institutes of Health.)

Eurosurveillance projection: 77,181 to 277,124 additional cases by the end of 2014 (This projection, from a report in the peer-reviewed journal's Sept. 11 edition, assumes continued exponential growth, which the authors say is unlikely.)

Ebola: background numbers

Incubation period for Ebola from the time of infection to symptoms: 2 to 21 days

Worst previous Ebola outbreak, by number of deaths: 280 deaths out of 318 cases, in Zaire, 1976 (That was also the first recognition of the disease.)

Worst previous Ebola outbreak, by number of cases: 425 cases in Uganda 2000-01 (The death toll was 224.)

Number of Ebola vaccines getting fast-tracked through the approval process: 2  (One designed by scientists at the U.S. National Institutes of Health and licensed to GlaxoSmithKline, began human trials earlier in September. The second vaccine, identified by many scientists as more promising, was developed by scientists at the National Microbiology Laboratory in Winnipeg. The federal government has licensed the vaccine to NewLink Genetics, a small biotech company in Ames, Iowa.)