Ebola virus is a particularly dangerous viral infection caused by the Ebola virus and occurring with severe hemorrhagic syndrome. The initial clinical signs of Ebola virus include high fever and severe intoxication, catarrhal phenomena; during the peak period, indomitable vomiting, diarrhea, abdominal pain, hemorrhages in the form of skin hemorrhages, external and internal bleeding are added. Specific diagnosis is carried out using virological and serological methods. Etiotropic therapy has not been developed; a positive effect was obtained from the administration of plasma convalescents to patients. Pathogenetic measures are aimed at combating infectious and toxic shock, dehydration, hemorrhagic syndrome.
Ebola virus is a highly contagious viral disease from the group of hemorrhagic fevers, characterized by an extremely severe course and high mortality. Ebola first declared itself in 1976, when two outbreaks of infection were simultaneously registered in Sudan and Zaire (Congo). The fever got its name in honor of the Ebola River in Zaire, where the virus was first isolated.
The latest outbreak of Ebola in West Africa, which began in March 2014, is the most massive and severe since the virus was discovered. During this epidemic, more people got sick and died than in all previous years. In addition, for the first time, the virus crossed not only land, but also water borders, ending up in North America and Europe. The mortality rate in epidemic outbreaks of Ebola virus reaches 90%. In August 2014 WHO has recognized Ebola as a worldwide threat.
The Ebola virus belongs to the filovirus family and is morphologically similar to the virus that causes Marburg hemorrhagic fever, but differs from the latter in antigenic terms. There are 5 known types of Ebola virus: Zaire ebolavirus (Zaire), Sudan ebolavirus (Sudan), Tai Forest ebolavirus (Tai Forest), Bundibugyo ebolavirus (Bundibugio), Reston ebolavirus (Reston). Major outbreaks of Ebola in Africa are associated with the ebolaviruses Zaire, Sudan and Bundibugio; the 2014 epidemic was caused by the Zaire virus. Reston ebolavirus does not pose a danger to humans.
It is assumed that the natural reservoir of the Ebola virus is bats, chimpanzees, gorillas, forest antelopes, porcupines and other animals living in equatorial forests. Primary human infection occurs through contact with the blood, secretions or corpses of infected animals. Further spread of the virus from person to person is possible by contact, injection, sexual intercourse. Most often, Ebola infection occurs through direct contact with the biological material of sick people, contaminated bedding and care items, with the body of the deceased during funeral rites, joint meals with the patient, less often – during sexual contact, etc. Patients with Ebola pose a high danger to others for about 3 weeks from the onset of the disease, secreting the virus with saliva, nasopharyngeal mucus, blood, urine, semen, etc.
Microtraumatic skin and mucous membranes serve as the entrance gate of infection, but there are no local changes in the focus of the virus introduction. The primary reproduction of the virus occurs in the regional lymph nodes and spleen, after which there is intense viremia and dissemination of the pathogen to various organs. Ebolavirus can have both a direct cytopathic effect and cause a complex of autoimmune reactions. As a result, platelet formation decreases, vascular endothelial cells are damaged, hemorrhages and foci of necrosis develop in internal organs, which in the clinical picture corresponds to signs of hepatitis, interstitial pneumonia, pulmonary edema, pancreatitis, orchitis, endarteritis of small arteries, etc. Autopsy reveals necrosis and hemorrhages in the liver, spleen, pancreas, adrenal glands, pituitary gland, gonads.
Family members and medical personnel caring for patients, as well as those involved in trapping and transporting monkeys, are at increased risk of contracting Ebola. After suffering from Ebola, a stable post-infectious immunity is formed; cases of re-infection are rare (no more than 5%).
The incubation period for Ebola virus lasts from several days to 14-21 days. This is followed by a sharp and sudden manifestation of clinical symptoms. In the initial period of Ebola virus, general infectious manifestations prevail: intense headache in the forehead and back of the head, neck and lower back pain, arthralgia, pronounced weakness, body temperature rise to 39-40 ° C, anorexia. Most patients have tickling and dryness in the throat (a feeling of a “rope” or a painful “ball”), the development of sore throat or ulcerative pharyngitis. With Ebola, abdominal pain and diarrhea occur almost from the first days. The patient’s face acquires a mask-like appearance with sunken eyes and an expression of longing; often patients are disoriented and aggressive.
From about 5-7 days, during the height of the clinical course of Ebola, there are chest pains, a painful dry cough. Abdominal pain increases, diarrhea becomes profuse and bloody, acute pancreatitis develops. From day 6-7, a bark-like rash appears on the skin of the lower half of the trunk, the extensor surfaces of the limbs. Ulcerative vulvitis and orchitis often occur. At the same time, hemorrhagic syndrome develops, characterized by hemorrhages at injection sites, nasal, uterine, gastrointestinal bleeding. Massive blood loss, infectious-toxic and hypovolemic shock cause the death of Ebola patients at the beginning of the 2nd week of the disease.
In favorable cases, clinical recovery occurs after 2-3 weeks, but the period of convalescence stretches for 2-3 months. At this time, asthenic syndrome, poor appetite, cachexia, abdominal pain, hair loss, sometimes hearing loss, vision loss, mental disorders develop.
Ebola can be suspected in people with characteristic clinical symptoms who are in epidemiologically disadvantaged regions of Africa or who have been in contact with patients. Specific diagnostics of infection are carried out in special virological laboratories in compliance with the requirements of increased biological safety. Ebolavirus can be isolated from saliva, urine, blood, nasopharyngeal mucus and other biological fluids by infecting cell cultures, RT-PCR, electron microscopy of skin and internal organ biopsies. Serological diagnosis of Ebola virus is based on the detection of antibodies to the virus by ELISA, RPH, IFT, etc.
Nonspecific changes in the general blood test include anemia, leukopenia (later – leukocytosis), thrombocytopenia; in the general urine analysis – pronounced proteinuria. Biochemical changes in the blood are characterized by azotemia, an increase in the activity of transferases and amylase; when examining the coagulogram, signs of hypocoagulation are revealed; blood CBS – signs of metabolic acidosis. In order to assess the severity of the course and prognosis of Ebola virus, patients may need chest X-ray, ECG, ultrasound of the abdominal cavity, FGS. Differential diagnosis is carried out with malaria, septicemia, typhus, other hemorrhagic fevers, primarily with Marburg fever, Lassa fever, yellow fever. Patients may be shown consultations of an infectious disease specialist, gastroenterologist, neurologist, hematologist and other specialists.
Transportation and treatment of Ebola patients is carried out in special isolation boxes. All nursing staff must undergo special instruction, use barrier protective equipment (special suits, goggles, respirators, gloves, shoes, etc.), recommended for such particularly dangerous infections as plague and smallpox. Strict bed rest and round-the-clock medical supervision are organized for the patient.
To date, there is no vaccine against Ebola; experimental samples are being tested in several countries around the world. Treatment is mainly reduced to symptomatic measures: detoxification therapy, fight against dehydration, hemorrhagic syndrome, shock. In some cases, the introduction of plasma of recovered people gives a positive effect.
Prognosis and prevention
The mortality rate from Ebola caused by the Zaire virus strain reaches almost 90%, the Sudan strain – 50%. The criteria for recovery are considered to be normalization of the general condition of the patient and three-fold negative results of virological studies. Tracking the contacts of patients, compliance with personal protection measures, safe burial of the deceased, disinfection of biological materials from patients with hemorrhagic fevers allows to stop the spread of Ebola. Sanitary quarantine control of passengers arriving from Africa has been strengthened at airports in various countries. Contact persons are subject to observation within 21 days. If Ebola virus infection is suspected, the patient is injected with a specific immunoglobulin from the blood serum of horses.