Ebola questions and answers: transmission, infection and false negative test results

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There is a lot of confusing - and often contradictory - information about the Ebola virus circulating.

Hopefully this Q&A will clear things up.

Q: What IS the Ebola virus?

A: Ebola is an infection with a virus of the family Filoviridae, genus Ebolavirus. So far, only two members of this family of viruses have been identified - Marburgvirus and Ebolavirus.

Five subspecies of Ebolavirus have been identified, four of which can cause disease in humans:

• Ebola virus (Zaire ebolavirus)


• Sudan virus (Sudan ebolavirus)


• Taï Forest virus (Taï Forest ebolavirus, formerly Côte d'Ivoire ebolavirus)


• Bundibugyo virus (Bundibugyo ebolavirus)


• Reston virus (Reston ebolavirus): This is the one that has not caused disease in humans (but it can be fatal in non-human primates). This is the strain that killed dozens of lab monkeys at a research facility in Reston, VA, in 1989. Four workers at that facility tested positive for Ebola. In 1996, nine lab workers were exposed to this strain after handling infected animals. None of those infected developed symptoms or became ill, but they did develop antibodies to the strain. It is possible that the Reston strain can be transmitted via small-particle aerosols (airborne), but that hasn't been confirmed.

Q: When - and how - was Ebola discovered?

A: Ebola was discovered in 1976, during the first known human outbreaks - 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.

The Zaire outbreak killed 280 people (88% fatality rate). The Sudan outbreak killed 151 (53% fatality rate). Those numbers are for reported cases. One person in England was infected with the Sudan subtype - that infection occurred via an accidental needle stick in a lab. That person survived.

Professor Peter Piot, the Director of the London School of Hygiene and Tropical Medicine, was on the team that discovered Ebola. In a recent interview with The Guardian, Dr. Piot explained that the virus was discovered when a blood sample was brought to his lab in Belgium, with a request to test it for yellow fever. Using an electron microscope, he created an image of the virus and noticed it looked similar to the extremely dangerous Marburg virus, which causes a hemorrhagic fever. A short time later, the American Centres for Disease Control determined that it wasn't the Marburg virus, but a related, unknown virus.

To read the fascinating interview in its entirety, click here: 'In 1976 I discovered Ebola, now I fear an unimaginable tragedy'

Q: What are the symptoms of Ebola?

A. The CDC lists the following symptoms:

• Fever (greater than 38.6°C or 101.5°F)


• Severe headache


• Muscle pain


• Weakness


• Diarrhea


• Vomiting


• Abdominal (stomach) pain


• Unexplained hemorrhage (bleeding or bruising)

Symptoms may appear anywhere from 2 to 21 days after exposure to Ebola, but the average is 8 to 10 days.

Early diagnosis can be tricky, because in the beginning stages of the illness, symptoms (like fever, headache, and muscle pain) are similar to those of the flu or other less deadly viruses.

But within a few days, a person infected with Ebola will become quite sick. Gastrointestinal illness, such as abdominal pain, vomiting and diarrhea will occur. Some people have trouble breathing and swallowing, experience chest pain, and develop a rash, excessive bruising and bloody blisters of the skin.

In the advanced stages of an Ebola infection, internal bleeding (viral hemorrhagic fever) usually occurs. Ebola can cause hemorrhaging of multiple organs. External bleeding from various orifices of the body, including the ears and eyes, is what many think of when they hear "Ebola", but not all who are infected exhibit those symptoms.

The Ebola virus itself isn't what kills people - the immune system's reaction does. For more on that, please read Ebola: How it Kills May Surprise You.

Q: How is Ebola transmitted?

A: Here's where things get tricky. Initially, the CDC website contained vague information about transmission.

As of September 9, here's what the site said:

When an infection does occur in humans, the virus can be spread in several ways to others. The virus is spread through direct contact (through broken skin or mucous membranes) with

• a sick person's blood or body fluids (urine, saliva, feces, vomit, and semen)


• objects (such as needles) that have been contaminated with infected body fluids


• infected animals

Healthcare workers and the family and friends in close contact with Ebola patients are at the highest risk of getting sick because they may come in contact with infected blood or body fluids.

On September 11, it said:

How is Ebola spread?

The virus is spread through direct contact (through broken skin or mucous membranes) with blood and body fluids (urine, feces, saliva, vomit, and semen) of a person who is sick with Ebola, or with objects (like needles) that have been contaminated with the virus. Ebola is not spread through the air or by water or, in general, by food; however, in Africa, Ebola may be spread as a result of handling bushmeat (wild animals hunted for food) and contact with infected bats.

As of September 22, it says (emphasis mine):

Can Ebola spread by coughing? By sneezing?

Unlike respiratory illnesses like measles or chickenpox, which can be transmitted by virus particles that remain suspended in the air after an infected person coughs or sneezes, Ebola is transmitted by direct contact with body fluids of a person who has symptoms of Ebola disease. Although coughing and sneezing are not common symptoms of Ebola, if a symptomatic patient with Ebola coughs or sneezes on someone, and saliva or mucus come into contact with that person's eyes, nose or mouth, these fluids may transmit the disease.

What does "direct contact" mean?

Direct contact means that body fluids (blood, saliva, mucus, vomit, urine, or feces) from an infected person (alive or dead) have touched someone's eyes, nose, or mouth or an open cut, wound, or abrasion.

How long does Ebola live outside the body?

Ebola is killed with hospital-grade disinfectants (such as household bleach). Ebola on dried on surfaces such as doorknobs and countertops can survive for several hours; however, virus in body fluids (such as blood) can survive up to several days at room temperature.

A 2007 study showed that the Ebola virus CAN be transmitted via fomites (inanimate objects like clothing, sheets, soap, furniture, or countertops, that are capable of transmitting infectious organisms from one person to another). That study found that the risk is low when infection control guidelines are followed.

The CDC has NOT been consistent about the possibility of Ebola transmission via fomites. Their own bulletins have been contradictory. For a lot more detail about this issue, please read Even the CDC Isn't Totally Sold on its Own Proclamations on How Ebola Is Transmitted.

The European Centre for Disease Prevention and Control says the following about fomite transmission:

Transmission through heavily contaminated fomites is apparently possible (source).

The virus can also be transmitted through material heavily contaminated with such fluids (source).

Experts say that the disease isn't contagious before an infected person develops symptoms.

The risk of infection is higher in the later stages of the disease. The sicker the person, the more infectious they are. Corpses carry the highest risk. In West African countries, burial rituals involve close contact with the dead.

Once a person has fully recovered from the virus, they are no longer contagious - with one VERY IMPORTANT exception - the Ebola virus has been found in semen 3 months AFTER recovery. Because the virus can be transmitted through sexual contact, abstinence or condom use is recommended.

Regarding airborne transmission: There has been a LOT of confusion about the possibility of Ebola virus being airborne. Some experts say it is NOT transmissible via airborne particles. Some say it MIGHT be. Still others say it MAY become airborne if it keeps spreading and mutating.

Bottom line: It is probably better to be safe than sorry regarding fomite and airborne transmission. Practice careful hygiene as you would to avoid any other contagious illness.

Q: How have so many medical professionals become infected?

A: As of September 28, 2014, 377 healthcare workers have been infected with Ebola (during the current outbreak). Of those, 216 have died, according to the World Health Organization (WHO).

If anyone should know how to protect themselves against such a deadly disease, it would be those trained to handle and treat it.

But a lack of resources, under-staffing, poor protection, and unsanitary conditions are huge issues in the West African countries affected by Ebola. They are simply overwhelmed by the magnitude of the outbreak.

Jon Cohen of Science Insider interviewed two healthcare workers who survived Ebola infection. He asked each how they think they became infected.

The first is Dr. Senga Omeonga, who became infected while working in Liberia. He told Cohen that a lack of protective equipment, patients lying about symptoms, and inadequate protective gear are possible reasons.

But he also thinks he knows the specific patient interaction that infected him:

I had to deal with a patient who initially was negative and we were treating him, and he had no improvement. They requested a second test and it came back positive after 10 days. I was exposed to that patient day by day. With light PPE. I don't think I had enough protection in the hospital. Somehow I was contaminated by touching him.

Cohen asked Dr. Omeonga if he came in contact with fluid. His response:

It's hard to tell. He was a wet patient - he was having diarrhea and vomiting. Probably somewhere I touched him. At the time he was declared negative, I was sitting in his room talking to him and being close to him. I don't really remember direct contact. Maybe the last few days when he was almost abandoned. Everyone was afraid to touch him. He was screaming. I removed his nasogastric tube and he was fighting. I had my face shield and mask on.

Maybe it was in the beginning, when I was sitting in his room. Sometimes I had just a T-shirt on. I don't know. There are lots of questions. Every day I'm still thinking: "When was I contaminated?"

The second healthcare worker Cohen interviewed was Nancy Writebol, a clinical nurse associate from the US who worked with the missionary group SIM in Liberia.

When asked how she thinks she contracted Ebola, here's what she said:

I don't know how I became infected and how I contracted it. There are some thoughts about how I might have gotten it. Nobody is really sure, least of all me. I never felt like I was unsafe and I never felt like I walked into a situation where I was being exposed. I was on the low-risk side of things. I never was in the crisis or the Ebola center. I was always on the outside. I made sure doctors and nurses were dressed properly before they went in, and I decontaminated them before they went out. We kept a close check on each other about whether people felt safe.

Dr. Kent Brantly, who worked in Liberia, does not know how he contracted Ebola either. He said he is sure he didn't violate any safety guidelines. Dr. Rick Sacra, another American doctor who caught the virus in Liberia, did not treat Ebola patients. He worked in the obstetrics ward, which is separate from the Ebola isolation unit, and followed all safety precautions (including wearing protective gear).

Q: How is Ebola virus infection diagnosed?

A: Early diagnosis is tricky, because at the beginning of infection symptoms are non-specific and could represent more common diseases.

If a person has early symptoms AND has had contact with someone sick with Ebola, or has been in an impacted region, the protocol is to isolate them and notify public health officials.

Laboratory tests used in diagnosis are the following.

From the CDC:

Within a few days after symptoms begin:

• Antigen-capture enzyme-linked immunosorbent assay (ELISA) testing


• IgM ELISA


• Polymerase chain reaction (PCR)


• Virus isolation

Later in disease course or after recovery:

• IgM and IgG antibodies

These testing methods take anywhere from 12 hours to four days to show results.

Those tests are not entirely foolproof, though:

One test for Ebola, the indirect fluorescence assay, is known to have a rather low specificity , and therefore a rather high false negative rate. PCR testing has also been known to miss cases of affliction. (source)

In other words, it is possible for an Ebola test to be negative when the person actually does have Ebola.

Dr. Brantly's first Ebola test was negative:

According to Dr. Brantly's employer, Samaritan's Purse, a U.S.-based international relief organization that has operated in Liberia for 13 years, Dr. Brantly first felt ill July 23 but tested negative. Despite that negative result, he was placed into isolation - a provident decision. His symptoms soon worsened, and a repeat test on Friday night showed evidence of the virus. (source)

Rapid tests that show results IMMEDIATELY have been developed, but have yet to be approved for use.

Q: How is Ebola treated?

A: Because Ebola is a viral infection, antibiotics are ineffective. Currently, treatment involves handling symptoms (supportive care).

From the CDC:

The following basic interventions, when used early, can significantly improve the chances of survival:

• Providing intravenous fluids (IV)and balancing electrolytes (body salts)


• Maintaining oxygen status and blood pressure


• Treating other infections if they occur

There isn't a vaccine, anti-viral drug, or other approved medication for Ebola - yet.

ZMapp is an experimental drug that has not been tested for safety or efficacy yet. It is not a vaccine - it is a therapeutic drug. Nancy Writebol and Dr. Brantly were given this treatment, but no one knows if it influenced their recovery. Of the seven people given the drug so far, two have died. Dr. Omeonga was also given ZMapp.

Dr. Sacra was not given ZMapp - he was given an experimental Tekmira Pharmaceuticals drug called TKM-Ebola for a week after he arrived in the US for treatment. Dr. Sacra also received two blood transfusions from Dr. Brantly. These blood transfusions are believed to help a patient fight off the Ebola virus because the survivor's blood carries antibodies for the disease. Dr. Brantly also received blood from a recovered patient.

At recent WHO meeting, over 200 experts agreed that convalescent blood and plasma therapies (using blood from Ebola survivors) should be prioritized as a treatment option to consider. This method was used during the 1995 Ebola outbreak in Kikwit, Democratic Republic of Congo. Whole blood collected from recovered patients was given to eight patients. Seven of the eight recovered.

Dr. Brantly, Dr. Sacra, and an unnamed foreign doctor were treated with convalescent blood, and all three recovered.

Q: Does infection and recovery from Ebola provide lifetime immunity from the disease?

A: People who recover from Ebola infection develop antibodies that last for at least 10 years, possibly longer. It isn't known if people who recover are immune for life or if they can become infected with a different species of Ebola. Some people who have recovered from Ebola have developed long-term complications, such as joint and vision problems.

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