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An outbreak is the occurrence of more cases (patients) with an infectious disease than would normally be expected for a particular time, place or population. For most outbreaks, infections in two or more people may be linked (if they present with the same symptoms, occurring in the same area and time). For diseases not normally present in a population (such as EVD), even one ‘case’ is considered an outbreak.
Even a single case of a viral haemorrhagic fever like Ebola is an outbreak.
An outbreak case definition is a set of criteria for deciding who should be classified as a case and therefore be included in an outbreak investigation. It is needed when confirming that an outbreak exists, or when estimating the number of people infected. This definition helps healthcare workers decide which patients to classify as suspected disease cases (while waiting for results of confirmatory laboratory tests). The case definition criteria usually combine clinical symptoms or signs and epidemiological risk factors (i.e. travel, time, place and contact with the disease). A case definition is important in identifying people who are suspected of having Ebola.
A case definition helps to identify persons with suspected Ebola.
A person with signs and/or symptoms of Ebola:
The epidemiological risk factor in an Ebola outbreak is based on the probability that the patient has been in contact with someone with Ebola. The epidemiologic risk factor is further classified into 4 risk categories (high, medium, low and no risk) based on the degree of contact with person/s with Ebola and the level of protection used by the exposed individual.
|Risk category||Criteria (any of the following)|
|High risk||Percutaneous (e.g. needle-stick) or mucous membrane exposure to blood or body fluids of a person with Ebola while the person was symptomatic|
|Exposure to the blood or body fluids of a person with Ebola while the person was symptomatic without appropriate personal protective equipment (PPE)|
|Processing blood or body fluids of a person with Ebola while the person was symptomatic without appropriate PPE or standard biosafety precautions|
|Direct contact with a dead body without appropriate PPE in a country with widespread Ebola virus transmission (Guinea, Liberia, Sierra Leone or Mali)|
|Having lived in the immediate household and provided direct care to a person with Ebola while the person was symptomatic.|
|Some risk||In countries with widespread Ebola virus transmission: direct contact while using appropriate PPE with a person with Ebola while the person was symptomatic or with the person's body fluids or any direct patient care in other healthcare settings|
|Close contact in households, healthcare facilities, or community settings with a person with Ebola while the person was symptomatic|
|Close contact is defined as a prolonged time within 1 metre of a person with Ebola while the person was symptomatic and not wearing PPE.|
|Low risk||Having been in a country with widespread Ebola virus transmission within the past 21 days but with no known exposures|
|Having brief direct contact (e.g. shaking hands) while not wearing appropriate PPE, with a person with Ebola while the person was in the early stage of disease|
|Brief near (but not touching) a person with Ebola while the person was symptomatic|
|In any other country, direct contact while using appropriate PPE with a person with Ebola while the person was symptomatic|
|Travel on an aircraft with a person with Ebola while the person was symptomatic.|
|No risk||Contact with an asymptomatic person who had contact with a person with Ebola|
|Contact with a person with Ebola before the person developed symptoms|
|Having been more than 21 days ago to a country with widespread Ebola virus transmission.|
A person with suspected Ebola must have both symptoms of disease and an epidemiological risk factor within the 21 days before the symptoms began.
The early symptoms of Ebola are non-specific (vague). Symptoms usually start between 4 and 10 days, or as late as 21 days after virus exposure. Common symptoms include:
Common symptoms of Ebola are fever, diarrhoea, vomiting, stomach pain, headache, muscle pain, weakness, and in some cases, bleeding.
At the time of exposure, Ebola virus enters the body through mucous membranes (eyes, nose, mouth) or through broken skin. The virus then invades many different types of cells but particularly the epithelial cells lining the body cavities and blood vessels. The virus multiplies in these cells, causing them to burst and die, with the spread of new virus to other cells. During the incubation period (when patients are not infectious), viral multiplication continues until enough cells are affected to cause disease symptoms. Ebola patients are most contagious (infectious) at or shortly after death when the level of virus multiplication peaks and extravasation (leakage) of fluids from the body is high.
Ebola patients are most contagious at or shortly after death.
The most common complications of Ebola include:
Most patients progress to develop severe symptoms and disease complications by day 7 of illness. About 60-70% of patients die, although death estimates are variable. For those who do recover (less than 30% in the current West African outbreak), improvement occurs around day 10 with discharge often possible by day 14.
The death rate in the current Ebola outbreak is around 70%.
There are many diseases (both infectious and non-infectious) that have symptoms and signs resembling those of Ebola. For this reason, it is very important that a laboratory sample is submitted to confirm the Ebola diagnosis. Additional laboratory samples may be necessary to exclude other common conditions, e.g. malaria. All patients should either be tested for malaria, or given empiric (presumptive) malaria treatment. Patients should be started on malaria treatment while waiting for results of both malaria and Ebola tests.
Many diseases, both infectious and non-infectious, may mimic Ebola.
Persons with symptoms and signs of Ebola should be taken to an Ebola Treatment Unit (ETU) for medical assessment and isolation. Ideally patients should be transported individually. If this is not possible, patients should be transported so that they are not touching each other, and not in contact with body fluids such as vomit or diarrhoea from other patients.
In the worst affected countries, healthcare resources are limited with few ambulances available. In many cases, civilians have to transport sick patients to an ETU. Ideally these individuals should avoid all direct contact (touching) with the sick person and their body fluids. This implies trying to keep a ‘safe space’ around your person, not touching anything unnecessarily, washing hands often and keeping about 2-3 metres away from people. Where close contact is unavoidable, civilians should wear disposable gloves (or if nothing else is available, even plastic bags over their hands), cover their eyes with glasses or sunglasses and wear a face-cover or handkerchief over their mouths.
For healthcare personnel transporting suspected Ebola patients, personal protective equipment (PPE) should be worn (including coveralls or gowns, aprons, gloves, visors or goggles, respirators and boots or shoe covers, as described in chapter 3). All transport vehicles (private cars and ambulances) should be thoroughly cleaned with soap and water, followed by disinfection with a 0.5% chlorine-based solution (while wearing PPE to avoid mucous membrane splashes).
Precautions should be taken when transporting persons with suspected Ebola.
Triage is the early sorting of patients at the point of entry to a health facility. The Centers for Disease Control (CDC) recommends a triage approach called ‘Identify, Isolate and Inform’. This ensures Ebola suspects are identified upon arrival at a facility using screening questions about possible Ebola exposure and symptoms (based on the case definition). They should then be isolated (removed from general patient areas to a separate area). The relevant authorities and facility staff should be informed of the possible Ebola case.
Wherever possible, patients who meet the case definition of Ebola should be taken to a designated ETU (rather than a routine health facility) where access to Ebola laboratory testing, isolation facilities and appropriate PPE for healthcare workers is available. Within ETUs, admitted patients are kept in an ‘Ebola suspect’ area while awaiting Ebola confirmatory blood tests. If found to be positive, the patient should be moved to a ‘confirmed Ebola’ isolation area. At times beds may be unavailable, so some units will only admit patients with disease complications, e.g. dehydration, shock or organ failure.
In cases where a person with suspected Ebola presents to a routine healthcare facility, i.e. not a designated ETU, healthcare workers should have a standard operating procedure in place.
Where Ebola is suspected, patients should be immediately isolated in a single room with dedicated staff to prevent infection of other patients and staff. The facility management and local ministry of health should be informed immediately.
Patients with suspected Ebola must immediately be isolated from other patients to reduce the risk of spreading the infection.
In an ETU suspect isolation area, there may be patients who turn out not to have Ebola (with another cause for their symptoms) and patients who do have Ebola. It is very important that patients admitted to the suspect area are counselled to keep their distance from other patients, and that excellent hygiene is maintained. If carers are admitted together with young children, an alternative carer to look after the children is preferable. (Some ETUs are using Ebola survivors for this role.)
Pregnant women are at high risk of severe disease: the placenta, amniotic fluid and fetus are highly infectious. Pregnant women may present with unexplained vaginal bleeding, miscarriage or labour, or may miscarry or deliver while in the ETU. If possible, pregnant women should be separated from other patients in a suspect area. Breastfeeding women should stop breastfeeding, and the baby given formula instead.
Although most persons with Ebola are extremely ill and require hospitalisation, successful home-based, community care for Ebola cases has been reported. In some instances, community health workers and Ebola survivors have been able to provide limited supportive care by providing patients with food and rehydration fluids only. However, the risk of disease transmission to caregivers is high, so they should receive clear instructions on how to avoid becoming infected and how to safely decontaminate the patient’s home (see chapter 5).
There is currently no approved medicine for specific treatment of Ebola. Patient care focuses on treating symptoms and complications as they appear (so-called supportive care). The key elements of supportive care (which if started early may improve chances of survival) are:
The level of supportive care provided will depend on the resources available and the policy of the individual healthcare facility or ETU. Given the extremely limited healthcare resources and the very high risk of Ebola transmission to healthcare workers, some ETUs provide basic supportive care only. The mainstay of therapy is oral fluid and electrolyte replacement with oral rehydration solution in mild to moderately severe cases where the patients can tolerate oral administration; in severe cases intravenous fluid replacement is essential to prevent death from renal failure. In severely resource-constrained settings, patients who are recovering have helped and encouraged very ill and dehydrated patients to drink and maintain a good oral intake. In well-resourced settings, however, full intensive care facilities with intravenous therapy, mechanical ventilation, blood pressure support, renal dialysis and blood/blood product transfusion may be available.
Supportive care provides treatment for symptoms and complications of Ebola.
Ebola may co-infect patients with other common diseases (they have both Ebola plus another disease). Therefore, many ETUs provide routine treatment for these other conditions at patient admission. Anti-malarial drugs and broad-spectrum antibiotics (e.g. cephalosporins) are the most commonly used additional treatments. Common symptoms of Ebola that need treatment are fever (anti-pyretics), pain (analgesia), nausea and vomiting (anti-emetics) and anxiety/agitation (anxiolytics or sedatives).
Pregnant women with Ebola are a group at increased risk of severe disease and death. Spontaneous abortion and pregnancy-related haemorrhage are common, posing additional risks to others. Intra-uterine fetal death is common at presentation. All live-born neonates to date have subsequently died. The fetus, placenta, amniotic fluid and breast milk are highly infectious, and remain infectious even if the mother survives and her blood subsequently tests negative for Ebola.
Patient temperature monitoring is not strictly necessary, as all patients are given anti-pyretics. It may be useful though in the recovery period, to document absence of fever. During patient observation rounds, symptoms and complications should be noted.
The purpose of recording these basic observations is to:
Any observations that require invasive procedures, e.g. blood glucose estimation, could potentially result in needle-stick injury to healthcare workers (with inoculation of the virus). For this reason all invasive procedures should be carefully considered. If the procedure is truly required, it should be conducted with adequate staff, good lighting, sharps containers and preferably with use of safety-engineered devices.
In the majority of ETUs in the 3 worst-affected countries, there are no facilities to provide intensive care for Ebola patients. In addition, there is an extremely high risk of Ebola transmission to healthcare workers during resuscitation attempts. For both these reasons, active attempts at patient resuscitation are not widely supported. In well-resourced settings, with ability to provide intensive care, resuscitation may be considered.
This is an extremely controversial topic, as surgery performed on patients with Ebola poses a serious risk of Ebola infection to healthcare workers that sustain needle-stick injuries or cuts. For this reason most ETUs to date have not performed surgical operations, although under ideal and controlled conditions, operations could be performed.
The psychological trauma suffered by Ebola patients is severe, with most survivors witnessing the death of fellow patients at an ETU and experiencing loss of some family members. In addition to this, many survivors are stigmatised or even ostracised by their communities when they return home. For this reason, extensive counselling and support should be provided to Ebola survivors, before and after discharge. However, given the scale of the current outbreak this will be challenging.
Patients whose major symptoms have resolved, who are fever-free for at least 3 days, have no significant ongoing symptoms and are able to care for themselves independently, may be considered for discharge. Some ETUs require a negative laboratory test for Ebola (the Ebola PCR) as a marker that the patient is no longer infectious prior to discharge.
Ebola patients who have clinically recovered and have been fever-free for at least 3 days can be considered for discharge.
There should be a defined discharge protocol and discharge area. When patients are discharged from the high-risk area, they need to wash thoroughly (soap and water) to remove virus contaminating their skin and hair. Patients’ clothing and shoes should be disinfected (by washing in 0.05% chlorine solution) before discharge or replaced if heavily contaminated.
The patient should be accompanied home by a healthcare worker (or community health worker/health promoter) to explain to the family and their community that they are no longer infectious. Most Ebola survivors will need ongoing care and support in the weeks following discharge to ensure food security, provide psychological support and establish successful re-integration into the community. Male patients should be counselled about the prolonged excretion of virus in semen (up to 3 months), and should be supplied with condoms on discharge.
Bodies are most infectious around and just after death. The reason is extravasation (leaking out) of blood and body fluids from the patient. Ebola virus is fragile but can survive up to 5 days or longer under favourable conditions. Whether in a healthcare facility or at home, a dead body must be treated with dignity and systems must be put in place for the family and relatives to give the person a decent send-off including permission to say prayers albeit from afar without contact with the body. The body must be handled with respect.
Only trained workers should be allowed to handle infected human remains. Personal protective equipment (PPE, preferably coveralls) should be used before contact with the body, both during collection and placement in body bags. The PPE should be removed with care not to contaminate the wearer, discarded appropriately and followed by handwashing with soap and water (if hands visibly soiled) or with 70% alcohol-based handrub or 0.05% chlorine solution (if not visibly contaminated).
The body should be prepared as follows:
Corpses of people who have died of Ebola are highly infectious and should be handled with great care.
Traditional burial practices in some West African countries involve washing and touching of the corpse by family members and people attending the burial. This traditional practice has been linked with many cases of Ebola transmission and is thought to play a major role in spreading Ebola. In order to avoid this risk, healthcare workers and ministries of health are trying to encourage communities to practise so-called ‘safe burials’ or cremations. This concept is at odds with social and cultural rituals, and so the procedure should be clearly explained to family members and community leaders, preferably with the help of a health promoter.
It is essential to allow the family to participate in the process in order to fulfil their traditional and personal needs. The following are suggested ways in which the family could be involved:
In the event of a death in the community, health promotion messaging should educate people not to touch and bury the corpse. A contact number for reporting of possible Ebola deaths should be available. Medical teams can then assess the risk and if necessary disinfect the house, safely prepare the corpse and assist the family with arrangements for a safe burial.
A 35-year old woman collapses at home after a short illness, with symptoms of vomiting, diarrhoea and fever. She attended the funeral of a family member (who had suspected Ebola) in a village in Guinea a week before, where she helped prepare the body. A concerned family member calls the local ambulance to take her to an Ebola Treatment Unit (ETU) for assessment.
Yes, she has both symptoms which suggest Ebola and an epidemiological risk factor (touching a possibly Ebola-infected corpse) within the 21 days before the onset of her symptoms.
For healthcare workers transporting suspected Ebola patients, full personal protective equipment (PPE) should be worn (including gown or coveralls, aprons, gloves, visors or goggles, respirators and boots). The ambulance should be thorough cleaned with soap and water, followed by disinfection with a 0.5% chlorine-based solution (while wearing PPE to avoid mucous membrane splashes).
On arrival at the ETU, staff should establish whether she meets the case definition, take blood samples for laboratory confirmation of Ebola and assess whether she has complications requiring admission. For patients requiring admission, supportive care is provided which includes rehydration and presumptive treatment for malaria and bacterial sepsis. Symptomatic treatment for fever, pain, nausea, vomiting, etc. will also be provided.
The woman’s corpse is highly contagious and so only trained workers would be allowed to prepare her body, while wearing full personal protective equipment (PPE). Her body should be wrapped in leak-proof plastic and placed in a single 150-micron thick zip-able body bag. Spraying of the outside of the cadaver bag with 0.05% chlorine is no longer recommended. Once ready for burial, the family should be allowed to assist with arrangements and attendance at the burial.
Staff at the ETU should arrange for contact tracing to identify other people who participated in the burial and others who had close contact with her after she developed symptoms (e.g. nursed her at home, washed her bedding and clothes, cleaned the house or was in contact with vomit, diarrhoea). Contacts need close monitoring for fever and symptoms during the 21-day incubation period. Education and counselling to her contacts will ensure they know what to do/who to contact if they are unwell. In addition, a home disinfection team should visit her house to clean and disinfect the contents and surfaces.