Ebola Virus Disease
Ebola virus disease (EVD) or Ebola hemorrhagic fever (EHF) is a disease of humans and other primates caused by an ebolavirus. Symptoms start two days to three weeks after contracting the virus, with a fever, sore throat, muscle pain, and headaches. Typically nausea, vomiting, and diarrhea follow, along with decreased functioning of the liver and kidneys. Around this time, affected people may begin to bleed both within the body and externally.
The virus may be acquired upon contact with blood or bodily fluids of an infected animal (commonly monkeys or fruit bats). Spread through the air has not been documented in the natural environment. Fruit bats are believed to carry and spread the virus without being affected. Once human infection occurs, the disease may spread between people as well. Male survivors may be able to transmit the disease via semen for nearly two months. In order to make the diagnosis, typically other diseases with similar symptoms such as malaria, cholera, and other viral hemorrhagic fevers are first excluded. To confirm the diagnosis, blood samples are tested for viral antibodies, viral RNA, or the virus itself.
Signs and symptoms of Ebola usually begin suddenly with a flu-like stage characterized by fatigue, fever, headaches, and joint, muscle, and abdominal pain.Vomiting, diarrhea and loss of appetite are also common.Less common symptoms include the following: sore throat, chest pain, hiccups, shortness of breath and trouble swallowing. The average time between contracting the infection and the start of symptoms is 8 to 10 days, but it can vary between 2 and 21 days.Skin manifestations may include a maculopapular rash (in about 50% of cases). Early symptoms of EVD may be similar to those of malaria, dengue fever, or other tropical fevers, before the disease progresses to the bleeding phase.
In 40–50% of cases, bleeding from puncture sites and mucous membranes (e.g. gastrointestinal tract, nose, vagina, and gums) has been reported. In the bleeding phase, which typically starts 5 to 7 days after first symptoms internal and subcutaneous bleeding may present itself through reddening of the eyes and bloody vomit.Bleeding into the skin may create petechiae, purpura, ecchymoses, and hematomas (especially around needle injection sites). Types of bleeding known to occur with Ebola virus disease include vomiting blood, coughing it up or blood in the stool. Heavy bleeding is rare and is usually confined to the gastrointestinal tract.In general, the development of bleeding symptoms often indicates a worse prognosis and this blood loss can result in death.All people infected show some symptoms of circulatory system involvement, including impaired blood clotting. If the infected person does not recover, death due to multiple organ dysfunction syndrome occurs within 7 to 16 days (usually between days 8 and 9) after first symptoms.
No ebolavirus-specific treatment exists.Treatment is primarily supportive in nature and includes minimizing invasive procedures, balancing fluids and electrolytes to counterdehydration, administration of anticoagulants early in infection to prevent or control disseminated intravascular coagulation, administration of procoagulants late in infection to control bleeding, maintaining oxygen levels, pain management, and the use of medications to treat bacterial or fungal secondary infections. Early treatment may increase the chance of survival.A number of experimental treatments are being studied.
In the United States, the FDA's animal efficacy rule can be used in combination with a phase I clinical trial to demonstrate reasonable safety for an experimental, unapproved drug, to obtain permission to treat people who are infected with Ebola with the drug under the Expanded access program. The Animal Efficacy Rule exists, because the normal path for testing the safety and efficacy of drugs is not possible for diseases caused by dangerous pathogens or toxins.The FDA allowed two drugs, ZMapp and an RNA interference drug called "TKM-Ebola", to be used in people infected with Ebola under these programs during the 2014 outbreak.
Life cycles of the Ebolavirus
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