There are currently five known strains of Ebola: Ebola-Zaire, Ebola-Sudan, Ebola-Taï Forest, Ebola-Bundibugyo and Ebola-Reston. Four of those strains are known to be harmful to humans. Three of those strains have led to people’s deaths. Two of those strains are responsible for hundreds of deaths. One strain has spread to four countries in West Africa and it is responsible for more than one thousand deaths. This is Ebola, by the numbers, past and present.
The first known human infections of Ebola-Reston occurred in 1990, but it is not thought to be harmful. There have been seven reported cases, but all have reportedly been asymptomatic and no one has ever died from it. All seven cases occurred in the United States.
There is only one known case of Ebola-Tai Forest, which occurred in 1994 when a scientist fell ill after reportedly conducting a necropsy on a chimpanzee. She flew to Switzerland, where she was treated and made a full recovery.
There are only two known outbreaks of Ebola-Bundibugyo, but both have occurred within the last seven years. There have been 226 reported cases to date, with 73 resulting in death, which is a 32 percent fatality rate. The first outbreak occurred from 2007-2008 in Uganda. The second and last outbreak occurred in 2012 in the Democratic Republic of the Congo.
The Ebola-Sudan strain was first discovered in 1976. Of its five reported outbreaks to date, there have been a total of 784 infections, resulting in 421 deaths, which is a 53 percent fatality rate. The highest fatality rate ever recorded from an Ebola-Sudan outbreak 71 percent, which occurred in 2012, the last known Ebola-Sudan outbreak to date. The lowest fatality rate ever recorded is 41 percent, which occurred in 2004. Fatality rates from the other three Ebola-Sudan outbreaks are 53 percent in 1976, 65 percent in 1979 and 53 percent in 2000 and 2001. All five reported outbreaks have occurred in Sudan or Uganda.
The first known outbreak of Ebola-Zaire occurred in 1976. Along with Ebola-Sudan, it is thought to be the oldest strain of Ebola. With 13 reported outbreaks since then, not including lab accidents where only one person was infected, it is the most common strain of Ebola. Unfortunately, it is also considered the most deadly. Even compared to the other two lethal strains of Ebola, the numbers for Ebola-Zaire are staggering. This strain has killed a total 2033 out of 3115 of its victims since its first outbreak in 1976, which is about a 65 percent fatality rate.
The highest fatality rate ever recorded for Ebola-Zaire is 91 percent, from a 2002 outbreak in the Democratic Republic of the Congo, when 10 of 11 people who contracted it died. The lowest recorded fatality rate from an Ebola-Zaire outbreak is 47 percent, which occurred from 2008-2009, also in the Democratic Republic of the Congo. Fatality rates for ten past outbreaks include 88 percent in 1976, 62 percent in 1994 and 1995, 77 percent in 1995 and 68 percent in 1996. The fatality rate was 74 percent from 1996-1997, 78 percent from 2001-2002, 90 percent from 2002-2003, 83 percent from 2003-2004, 82 percent in 2005 and 71 percent in 2007. All of these outbreaks occurred in the Democratic Republic of the Congo except for two that occurred in Gabon.
Unfortunately, the 13th outbreak of Ebola-Ziare is ongoing in West Africa, which has infected 1711 people, including Americans Dr. Kent Brantly and Nancy Writehol, both health workers in Liberia who are now being treated at Emory University Hospital in Atlanta. With 932 deaths and counting, the current outbreak has killed a little over 54 percent of those who have contracted the deadly disease, but since that includes people who are currently suffering from it and it is not known how many of them will die. The death rate will likely be higher once it is all over, the last patient recovers and the last victim is laid to rest.
As of today, the ongoing outbreak of Ebola-Zaire in West Africa has spread to four different countries: Guinea, Liberia, Sierra Leone and Nigeria. First reported in March, it is thought to have begun in Guinea, and then spread to Liberia, then to Sierra Leone and most recently, Nigeria. It is the biggest Ebola outbreak in history.
The first cases of Ebola in Guinea were reported on March 25 and the numbers have been climbing every day since then. With 495 cases, resulting in 363 deaths, it has a 71 percent fatality rate, the highest of all four countries affected by the outbreak.
On March 31, the virus was reported to have spread to Liberia. Since then, there have been 516 cases, resulting in 282 deaths, which is about a 55 percent fatality rate.
The virus was thought to be contained to Guinea and Liberia until May 27, when the first cases of Ebola in Sierra Leone were reported. Since then, there have been 691 cases, the highest of all four affected countries, but with 286 deaths, it had the lowest fatality rate of 41 percent until very recently, when the virus spread to Nigeria.
On July 27, the first case of Ebola in Nigeria was reported. On July 20, Patrick Sawyer, an American citizen, took a plane to Nigeria from Liberia, where he is said to have contracted Ebola from his sister. He began having symptoms of the disease while on the plane, and then collapsed once he arrived at the airport. He was then quarantined and taken to a Nigerian hospital, where he died five days later, but not before it spread to the one of the doctors there.
There is currently only one reported death from Ebola in Nigeria reflected by the Center for Disease Control and World Health Organization. Therefore, it has an 11 percent fatality rate, with nine cases. As of today, a nurse who took care of Sawyer in the hospital has died and she is reportedly, the second health worker who has died as a result of taking care of Sawyer. Unless Nigeria works fast to contain the Ebola outbreak that has recently spread to their country, the numbers will keep multiplying, and they too will face an uphill battle with one of the most lethal diseases known to mankind.
By Lindsey Dow