Ebola Fast Facts | CNN


Here’s a look at Ebola, a virus with a high fatality rate that was first identified in Africa in 1976.

Ebola hemorrhagic fever is a disease caused by one of five different Ebola viruses. Four of the strains can cause severe illness in humans and animals. The fifth, Reston virus, has caused illness in some animals, but not in humans.

The first human outbreaks occurred in 1976, one in northern Zaire (now Democratic Republic of the Congo) in central Africa: and the other, in southern Sudan (now South Sudan). The virus is named after the Ebola River, where the virus was first recognized in 1976, according to the Centers for Disease Control and Prevention (CDC).

Ebola is extremely infectious but not extremely contagious. It is infectious, because an infinitesimally small amount can cause illness. Laboratory experiments on nonhuman primates suggest that even a single virus may be enough to trigger a fatal infection.

Ebola is considered moderately contagious because the virus is not transmitted through the air.

Humans can be infected by other humans if they come in contact with body fluids from an infected person or contaminated objects from infected persons. Humans can also be exposed to the virus, for example, by butchering infected animals.

Symptoms of Ebola typically include: weakness, fever, aches, diarrhea, vomiting and stomach pain. Additional experiences include rash, red eyes, chest pain, throat soreness, difficulty breathing or swallowing and bleeding (including internal).

Typically, symptoms appear eight to 10 days after exposure to the virus, but the incubation period can span two to 21 days.

Ebola is not transmissible if someone is asymptomatic and usually not after someone has recovered from it. However, the virus has been found in the semen of men who have recovered from Ebola and possibly could be transmitted from contact with that semen.

There are five subspecies of the Ebola virus: Zaire ebolavirus (EBOV), Bundibugyo ebolavirus (BDBV), Sudan ebolavirus (SUDV), Taï Forest ebolavirus (TAFV) and Reston ebolavirus (RESTV).

Click here for the CDC’s list of known cases and outbreaks.

(Full historical timeline at bottom)

March 2014 – The CDC issues its initial announcement on an outbreak in Guinea, and reports of cases in Liberia and Sierra Leone.

April 16, 2014 – The New England Journal of Medicine publishes a report, speculating that the current outbreak’s Patient Zero was a 2-year-old from Guinea. The child died on December 6, 2013, followed by his mother, sister and grandmother over the next month.

August 8, 2014 – Experts at the World Health Organization (WHO) declare the Ebola epidemic ravaging West Africa an international health emergency that requires a coordinated global approach, describing it as the worst outbreak in the four-decade history of tracking the disease.

August 19, 2014 – Liberia’s President Ellen Johnson Sirleaf declares a nationwide curfew beginning August 20 and orders two communities to be completely quarantined, with no movement into or out of the areas.

September 16, 2014 – US President Barack Obama calls the efforts to combat the Ebola outbreak centered in West Africa “the largest international response in the history of the CDC.” Speaking from the CDC headquarters in Atlanta, Obama adds that “faced with this outbreak, the world is looking to” the United States to lead international efforts to combat the virus.

October 6, 2014 – A nurse’s assistant in Spain becomes the first person known to have contracted Ebola outside Africa in the current outbreak. The woman helped treat two Spanish missionaries, both of whom had contracted Ebola in West Africa, one in Liberia and the other in Sierra Leone. Both died after returning to Spain. On October 19, Spain’s Special Ebola Committee says that nurse’s aide Teresa Romero Ramos is considered free of the Ebola virus.

October 8, 2014 – Thomas Eric Duncan, a Liberian citizen who was visiting the United States, dies of Ebola in Dallas.

October 11, 2014 – Nina Pham, a Dallas nurse who cared for Duncan, tests positive for Ebola during a preliminary blood test. She is the first person to contract Ebola on American soil.

October 15, 2014 – Amber Vinson, a second Dallas nurse who cared for Duncan, is diagnosed with Ebola. Authorities say Vinson flew on a commercial jet from Cleveland to Dallas days before testing positive for Ebola.

October 20, 2014 – Under fire in the wake of Ebola cases involving two Dallas nurses, the CDC issues updated Ebola guidelines that stress the importance of more training and supervision, and recommend that no skin be exposed when workers are wearing personal protective equipment, or PPE.

October 23, 2014 – Craig Spencer, a 33-year-old doctor who recently returned from Guinea, tests positive for Ebola – the first case of the deadly virus in New York and the fourth diagnosed in the United States.

October 24, 2014 – In response to the New York Ebola case, the governors of New York and New Jersey announce that their states are stepping up airport screening beyond federal requirements for travelers from West Africa. The new protocol mandates a quarantine for any individual, including medical personnel, who has had direct contact with individuals infected with Ebola while in Liberia, Sierra Leone or Guinea. The policy allows the states to determine hospitalization or quarantine for up to 21 days for other travelers from affected countries.

January 18, 2015 – Mali is declared Ebola free after no new cases in 42 days.

February 22, 2015 – Liberia reopens its land border crossings shut down during the Ebola outbreak, and President Sirleaf also lifts a nationwide curfew imposed in August to help combat the virus.

May 9, 2015 – The WHO declares an end to the Ebola outbreak in Liberia. More than 4,000 people died.

November 2015 – Liberia’s health ministry says three new, confirmed cases of Ebola have emerged in the country.

December 29, 2015 – WHO declares Guinea is free of Ebola after 42 days pass since the last person confirmed to have the virus was tested negative for a second time.

January 14, 2016 – A statement is released by the UN stating that “For the first time since this devastating outbreak began, all known chains of transmission of Ebola in West Africa have been stopped and no new cases have been reported since the end of November.”

March 29, 2016 – The WHO director-general lifts the Public Health Emergency of International Concern related to the 2014-2016 Ebola outbreak in West Africa.

*Includes information about Ebola and other outbreaks resulting in more than 100 deaths or special cases.

1976 – First recognition of the EBOV disease is in Zaire (now Democratic Republic of the Congo). The outbreak has 318 reported human cases, leading to 280 deaths. An SUDV outbreak also occurs in Sudan (now South Sudan), which incurs 284 cases and 151 deaths.

1995 – An outbreak in the Democratic Republic of the Congo (DRC) leads to 315 reported cases and at least 250 deaths.

2000-2001 – A Ugandan outbreak (SUDV) results in 425 human cases and 224 deaths.

December 2002-April 2003 – An EBOV outbreak in ROC results in 143 reported cases and 128 deaths.

2007 – An EBOV outbreak occurs in the DRC, 187 of the 264 cases reported result in death. In late 2007, an outbreak in Uganda leads to 37 deaths, with 149 cases reported in total.

September 30, 2014 – Dr. Thomas Frieden, director of the CDC, announces the first diagnosed case of Ebola in the United States. The person has been hospitalized and isolated at Texas Health Presbyterian Hospital in Dallas since September 28.

July 31, 2015 – The CDC announces that a newly developed Ebola vaccine is “highly effective” and could help prevent its spread in the current and future outbreaks.

December 22, 2016 – The British medical journal The Lancet publishes a story about a new Ebola vaccine that tested 100% effective during trials of the drug. The study was conducted in Guinea with more than 11,000 people.

August 1, 2018 – The DRC’s Ministry of Health declares an Ebola virus outbreak in five health zones in North Kivu province and one health zone in Ituri province. On July 17, 2019, the WHO announces that the outbreak constitutes a public health emergency of international concern. On June 25, 2020, the DRC announces that the outbreak is officially over. A total of 3,481 cases were reported, including 2,299 deaths and 1,162 survivors.

August 12, 2019 – Two new Ebola treatments are proving so effective they are being offered to all patients in the DRC. Initial results found that 499 patients who received the two effective drugs had a higher chance of survival – the mortality rate for REGN-EB3 and mAb114 was 29% and 34% respectively. The two drugs worked even better for patients who were treated early – the mortality rate dropped to 6% for REGN-EB3 and 11% for mAb114, according to Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases and one of the researchers leading the trial.

December 19, 2019 – The US Food and Drug administration announces the approval of a vaccine for the prevention of the Ebola virus for the first time in the United States. The vaccine, Ervebo, was developed by Merck and protects against Ebola virus disease caused by Zaire ebolavirus in people 18 and older.

October 14, 2020 – Inmazeb (REGN-EB3), a mixture of three monoclonal antibodies, becomes the first FDA-approved treatment for the Ebola virus. In December, the FDA approves a second treatment, Ebanga (mAb114).

January 14, 2023 – Ugandan authorities officially declare the end of a recent Ebola outbreak after 42 consecutive days with no new cases.

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‘Unprecedented’ situation as two African countries report outbreaks of Marburg virus

For the first time, the world is seeing two simultaneous outbreaks of the Marburg virus – one in Equatorial Guinea, the other in Tanzania. The Marburg virus is just as deadly as Ebola, to which it is closely related, but it has been extremely rare until now.

The situation with the Marburg virus entered uncharted territory on March 21, when Tanzania announced an outbreak of the disease in addition to the one in Equatorial Guinea, on the other side of the African continent.

Five people have died out of eight confirmed cases as of April 6, according to the US Center for Disease Control (CDC), which issued a health alert warning that doctors in the US should “be aware of the potential for imported cases”, even if the risk of the disease reaching the US is low.

The situation in Equatorial Guinea currently seems the most worrying. The World Health Organisation (WHO) issued an alert on February 25 after the discovery of several suspected deaths from Marburg in two villages in the north of the country in early January.

Since the first cases appeared, there have been 15 confirmed cases of Marburg in Equatorial Guinea. According to a report by the country’s health ministry, eleven of those patients died just days after symptoms of the disease appeared – vomiting, diarrhoea, nausea and high fever.

But the WHO has concerns that the official tallies are underestimating the disease’s real toll. Indeed, the cases in Equatorial Guinea come from regions quite far from each other, which suggests there “may be undetected community spread of the virus in the country”, the CDC noted.

The WHO suspects that Equatorial Guinea is not being fully transparent in reporting cases.

“This is a problem – this unprecedented outbreak of the Marburg virus in two different countries,” said Paul Hunter, an epidemiologist at the University of East Anglia.

“There has been an acceleration in the number of Marburg virus outbreaks over recent years,” added Cesar Munoz-Fontela, a specialist in tropical infectious diseases at the Bernhard Nocht Institute for Tropical Medicine in Hamburg.

From bat caves to humans

First detected in humans in 1967 in the German city of Marburg, the virus has broken out a dozen times in Africa since the late 1970s. But until recent years, the was never more than one outbreak every three or four years.

A bat – namely the Egyptian fruit bat – is the virus’s natural host, and transmits it to humans either directly or via an intermediate host such as monkeys.

Most of these outbreaks have been small – affecting no more than a dozen people each time, according to official statistics. That is lucky because Marburg is one of the most deadly viruses along with Ebola, which also belongs to the filovirus family of diseases. The two related diseases have mortality rates as high as 90 percent.

This grim statistic was borne out in the two largest Marburg outbreaks. Between 1998 and 2000, 128 patients died out of a total of 154 confirmed cases in DR Congo. Four years later, Marburg struck Angola, killing 227 out of 252 infected patients.

Since then, specialists have concluded that it is possible to reduce the fatality rate with rapid medical intervention. But even with speedily provided care, the fatality rate is still close to 50 percent, according to the WHO.

No vaccine

Marburg is much more dangerous than Ebola because – unlike with Ebola – there is “no vaccine or post-exposure treatment”, said Munoz-Fontela. There is no vaccine because, until now, there has been “no market” for one. “Without the 2014 Ebola epidemic in West Africa, we wouldn’t have an Ebola vaccine,” he continued, referring to the Everbo jab created in 2015.

The 2014-2016 Ebola epidemic in West Africa killed more than 11,000 people.

The WHO said at the end of March that it was ready to test vaccine candidates in Equatorial Guinea and Tanzania – implementing a policy of rapid vaccine development it developed in response to the accelerating emergence of epidemics in recent years.

But this phenomenon of one new outbreak a year since 2020 may be a product of the “improved detection of infectious diseases in Africa since Ebola and Covid-19”, Hunter said.

National health authorities in Africa have become increasingly aware of the risk of such viruses spreading – and are consequently looking more actively and efficiently for potential outbreaks.

But this is not necessarily so reassuring, Munoz-Fontela pointed out, because it suggests that “we’ve missed Marburg virus outbreaks in the past”, meaning it is not as rare as previously thought.

Meanwhile, environmental conditions have become much more amenable to the spread of the virus. “Global warming and other human activities are increasing the risk of new diseases spreading,” Hunter said.

Notably, the encroachment of humans into the natural habitats of animals means that people are more readily exposed to new infectious diseases.

“In the past, a person could go into a forest, get infected by a bat in a cave, and then die far away from other people,” Hunter said. “But now the forest is retreating and humans are moving closer to animals’ natural habitats – so viruses spread more easily.”

Less transmissible than Covid-19

Scientists have suggested the same phenomenon of increased human exposure to animal habitats may have caused the emergence of Covid-19.

But there are important differences between Marburg and Covid-19. Thankfully, the outbreak of a global Marburg (or indeed Ebola) pandemic is a lot less likely than it proved to be in the case of the coronavirus.

First, Marburg only starts to become contagious at the same time symptoms start appearing, between two and 21 days after the virus has been contracted. So there is zero risk of undetected transmission by asymptomatic carriers.

Second, the Marburg virus is “much less easily transmissible than Covid-19”, Munoz-Fontela said. While the coronavirus spreads by respiratory droplets – with coughing and sneezing spreading it into the air – transmission of Marburg requires contact with the bodily fluids of an infected person.

On the other hand, it only takes a small amount of the Marburg pathogen to infect another person. “Most of the time, the disease spreads during the haemorrhagic phase of Marburg, exposing in particular healthcare workers and family members around the patient’s bedside,” Hunter noted.

Filoviruses also appear to be “more stable than coronaviruses such as Sars-CoV-2 [Covid-19],” Munoz-Fontela said. That means the virus is not likely to mutate – and that in turn means that a vaccine would not require regular updates to stay effective.

But in the meantime, development of vaccines against Marburg virus are only in the earliest stages. The WHO estimated that both ongoing outbreaks pose “moderate” risk at the regional level. “Equatorial Guinea has porous borders with Cameroon and Gabon, and so far the cases have appeared in geographically diffuse parts of the country. In Tanzania, the Kagera region has busy borders with Uganda, Rwanda and Burundi,” The New York Times noted.

The next few weeks will prove illuminating about how much the disease has spread, Hunter concluded: “No new cases have been reported, but it will take as long as three weeks to find out if contacts of the previous recorded cases have been infected.” 

This article was translated from the original in French.

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