Sunday, 30 November 2014

Ebola virus disease

Ebola virus disease (formerly known as Ebola hemorrhagic fever) is a serious, often fatal disease in humans
     The virus is transmitted to humans from wild animals and then spreads in the population through human transmission

     The average fatality rate is about 50%. In previous outbreaks, the rates went from 25% to 90%
     The first Ebola disease outbreaks occurred in remote villages in central Africa, near rainforests, but the recent outbreak in West Africa has affected large urban centers as well as rural areas
     The community participation is essential to control outbreaks. To be effective, the fight must be based on a set of interventions: in case management, surveillance and contact tracing, quality laboratory services, burials safely and social mobilization
     Early support centered care rehydration and symptomatic treatment improves survival rates. No approved treatment has so far demonstrated its ability to neutralize the virus, but several treatments (derived from blood, immunological or pharmacological) are under study
     There is currently no licensed vaccine against Ebola virus disease, but two candidates are being evaluated

General information

The Ebola virus causes an acute and severe, often fatal disease if left untreated. Ebola virus disease appeared for the first time in 1976, when two simultaneous outbreaks Nzara (Sudan) and Yambuku (Democratic Republic of Congo). Yambuku being located near the Ebola River, it gave its name to the disease

Soaring now raging in West Africa (the first cases were reported in March 2014) is the largest and most complex since the virus was discovered in 1976. It produced more cases and deaths than all met earlier outbreaks. This outbreak also has the particularity of having spread from one country to another, starting from Guinea to reach Sierra Leone and Liberia (crossing land borders), Nigeria (through a only air traveler) and Senegal (via a traveler arrived by land)

The most affected countries (Guinea, Sierra Leone and Liberia) have very fragile health systems, lack human resources and infrastructure, and emerging from long periods of conflict and instability. On August 8, the WHO Director-General said that this outbreak was a public health emergency of international concern

A separate outbreak unrelated to the one in West Africa, expressed in the District of Boende, an isolated region of Equateur, Democratic Republic of Congo

Family Filoviridae virus has three genres: Cuevavirus, Marburgvirus and Ebolavirus. Five species were identified: Zaire, Bundibugyo, Sudan, Reston and Tai Forest. The first three were associated with significant African outbreaks. The virus responsible for the outbreak in 2014 in West Africa belongs to the species Zaire

It is thought that fruit bats of the family Pteropodidae are the natural hosts of Ebola virus. It gets into the human population after close contact with blood, secretions, organs or bodily fluids of infected animals such as chimpanzees, gorillas, fruit-eating bats, monkeys, antelopes wood or porcupines found sick or dead in the rainforest

It then spreads by human transmission as a result of direct contact (broken skin or mucous membranes) with blood, secretions, organs or bodily fluids of infected persons or with surfaces and materials (eg, Linen bed, clothing) that have been contaminated by fluids

Health workers were often infected by treating suspected or confirmed cases of Ebola disease. This occurred in close contact with patients, when anti-infective precautions were not strictly enforced

Funeral rites in which the relatives and friends of the deceased are in direct contact with the body may also play a role in the transmission of Ebola.

The patients remain contagious until the virus is present in their blood and body fluids, including semen and breast milk. Sperm can continue to spread the virus up to seven weeks after clinical recovery.

The incubation period, that is to say the time between infection and the onset of symptoms, ranges from 2 to 21 days. As long as they do not present symptoms, humans are not contagious. The first symptoms are febrile sudden onset fatigue, muscle pain, headache and sore throat. They are followed by vomiting, diarrhea, rash, symptoms of kidney and liver failure and, in some cases, internal and external bleeding (eg, bleeding gums, blood in the stool). Laboratory tests revealed a white blood cell and platelet count, elevation of liver enzymes

Ebola virus disease can be difficult to distinguish from other infectious diseases such as malaria, typhoid fever and meningitis. The following investigations are used to confirm infection with Ebola virus is the cause of

     immunosorbent assay =ELISA
     detection tests by antigen capture
     serum neutralization test
     reverse transcription followed by polymerase chain reaction  RT-PCR
     electron microscopy
     isolation of the virus in cell culture

Samples from patients present an extreme biohazard. Therefore, the laboratory analysis on non-inactivated samples should meet the conditions of the strongest possible containment
Treatment and vaccines

The support of oral rehydration or intravenous treatment of specific symptoms improve survival rates. No available treatment has so far proven against Ebola virus disease. However, a range of potential treatments, including blood products, immune therapies and drug treatments are being evaluated. No licensed vaccine is yet available, but it is currently assessing the safety of two potential vaccines in humans.
Prevention and control

In order to combat the outbreak, it is necessary to implement a set of interventions: in case management, surveillance and contact tracing, quality laboratory services, burials safely and social mobilization. The community participation is essential to control outbreaks. Awareness of the risk factors of infection by the Ebola virus and the possible protective measures is an effective way to reduce transmission in humans. The :
messages on risk reduction should focus on the following factors

     Reducing the risk of transmission between wildlife and humans by contact with fruit bats or monkeys / infected primates and eating the raw meat. We must handle animals with gloves and wear other protective clothing. The products from these animals (blood and meat) should be cooked thoroughly before consumption
     Reducing the risk of human transmission from direct contact or close to subjects with symptoms of Ebola, particularly with their body fluids. Then wear gloves and personal protective equipment when dealing in home sick. It should also be systematically wash hands after visiting to patients in the hospital or after handling sick at home
     Containment measures soaring including early and safe burial of the dead, identifying issues that may have been in contact with a person infected with Ebola, monitoring the health status of contacts for 21 days, separating healthy subjects / patients to prevent the spread, good hygiene and maintain a clean environment

Fight against infection in health care facilities

Health workers should always apply standard precautions when caring for patients, regardless of the presumed diagnosis. These precautions are the basic rules for hand hygiene, respiratory hygiene, use of personal protective equipment (to protect against splashing or other contact with infected materials) and safety injections and funeral rites

Health workers who care for suspected or confirmed cases of Ebola virus infection must, in addition to the precautions of use, take other infection control measures to avoid contact with blood or body fluids the patient or with contaminated surfaces and materials such as clothing and bed linen In close contact with sick (that is to say, less than a meter), they must wear face protection (face shield or surgical mask and goggles), a clean blouse, non sterile long sleeves and gloves ..sterile for medical procedures

Employees of laboratories are also at risk. Samples were collected on humans or animals in order to seek Ebola infection should be handled by trained staff and processed in suitably equipped laboratories
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