What is Ebola Haemorrhagic Fever?
Ebola haemorrhagic fever (Ebola febris haemorrhagica lat.) is an acute viral, highly contagious disease caused by the Ebola virus. A rare but very dangerous disease is mortality in 50-90% of clinical cases. It affects humans, some primates, and also, as it turned out, and pigs.
Causes of Ebola Haemorrhagic Fever
The Ebola virus was first identified in the equatorial province of Sudan and the surrounding areas of Zaire (now the Democratic Republic of Congo) in 1976. In Sudan, 284 people became ill, of whom 151 died. In Zaire, 318 (280 died). The virus was isolated in the area of the Ebola River in Zaire. This gave the name of the virus.
Ebola virus or simply Ebola is the common name for viruses of the same genus Ebolavirus belonging to the family of filoviruses that cause hemorrhagic Ebola fever in higher primates.
By its morphological properties, the virus coincides with the Marburg virus (Marburgvirus), but differs in antigenic terms. Both of these viruses belong to the family of filoviruses (Filoviridae). The Ebola virus is divided into five subtypes: Sudanese, Zaire, Ivory Coastal, Restonian, and Boundibuhio. Only 4 subtypes are affected. Asymptomatic leakage is characteristic of the Reston subtype. It is believed that the natural reservoirs of the virus are found in equatorial African forests.
This subtype was first recorded in Zaire, which is why it got its name. It has the highest mortality rate reaching 90%. The average mortality rate is around 83%. During the outbreak of 1976, the mortality rate was 88%, in 1994 – 59%, in 1995 – 81%, in 1996 – 73%, in 2001-2002 – 80%, in 2003 – 90%. The first outbreak was recorded on August 26, 1976 in the small town of Yambuku. The first case was a 44-year-old school teacher. The symptoms of the disease resembled the symptoms of malaria. It is believed that the initial spread of the virus was facilitated by the repeated use of needles for injection without sterilization.
This is the second subtype of the Ebola virus, recorded approximately simultaneously with the Zaire virus. It is believed that the first outbreak occurred among the workers of the factory in the small town of Nzara, Sudan. The carrier of this virus was never identified despite the fact that immediately after the outbreak, scientists tested the virus for various animals and insects in the vicinity of this town. The most recent outbreak was recorded in May 2004. On average, mortality rates were 54% in 1976, 68% in 1979, and 53% in 2000 and 2001.
This virus is classified as a type of Ebola virus, but it is believed that it may be a new virus of Asian origin. The virus was detected during the 1989 outbreak of monkey hemorrhagic fever virus (SHFV). It was established that the source of the virus was green macaques, which were brought to Germany in one of the research laboratories. After this, outbreaks were recorded in the Philippines, in Italy and in the USA (Texas). Although this subtype is of the Ebola species, it is not pathogenic for humans. Still a danger to monkeys.
Cote D’Ivoire ebolavirus
The virus was first detected in chimpanzees in the forest of Côte d’Ivoire, in Africa. On November 1, 1994, the bodies of two chimpanzees were discovered. An autopsy revealed the presence of blood in the cavities of some organs. A study of chimpanzee tissues gave the same results as studies of tissues of people who became ill with Ebola in Zaire and Sudan during 1976. Later, in the same year of 1994, other corpses of chimpanzees were found, in which the same Ebola virus subtype was found. One of the scientists who performed the autopsy of the dead monkeys fell ill with Ebola. Symptoms of the disease appeared a week after the autopsy of a chimpanzee. Immediately after that, the patient was taken to Switzerland for treatment, which, six weeks after infection, ended in complete recovery.
On November 24, 2007, the Uganda Ministry of Health announced an outbreak of Ebola in Bundibugio. After isolating the virus and analyzing it in the United States, the World Health Organization confirmed the presence of a new type of Ebola virus. On February 20, 2008, the Uganda Ministry of Health officially announced the end of the Bundibugio epidemic. In total, 149 cases of infection with this new type of Ebola were recorded, 37 of them were fatal.
The reservoir and source of infection in nature is poorly understood, most likely, it is mainly represented by a variety of rodents. The role of monkeys as sources of infection is not excluded. A sick person is very dangerous for others, 5-8 consecutive transmissions of the virus from the patient and the occurrence of nosocomial outbreaks of the disease are known. It was noted that at the first transfers the lethality was the highest (100%), then it decreased. The virus is detected in various organs, tissues and secretions: in the blood (7-10 days), nasal pharynx mucus, urine, semen. The patient is highly dangerous for 3 weeks from the onset of the disease; during the incubation period, the patient does not emit a virus.
The transmission mechanism is varied. The polytropic nature of the virus, the variety of ways of its excretion from the body determine the possibility of infection when in contact with the blood of patients, sexual and aerosol routes, when using common household items and sharing food. It has been established that infection during Ebola fever is mainly realized by direct contact with infected material. The disease is very contagious and is transmitted when a virus hits the skin and mucous membranes. The most dangerous is blood. The most at risk of infection is exposed to medical personnel in caring for the sick, as well as personnel engaged in catching, transporting monkeys and caring for them! quarantine period. The absence of diseases among people who were with patients in the same room, but who did not have close contact with them, made it possible to conclude that airborne transmission is unlikely.
The natural susceptibility of people is high. Post-infectious immunity resistant. Repeated cases of disease are rare; their frequency does not exceed 5%.
Major epidemiological signs. The foci of Ebola virus circulation are located in the zone of tropical rain forests of Central and West Africa (Zaire, Sudan, Nigeria, Liberia, Gabon, Senegal, Kenya, Cameroon, Ethiopia, Central African Republic). Outbreaks of Ebola fever in endemic foci are noted mainly in spring and summer. In Sudan (Nzara), the primary focus of infection arose among workers in a cotton factory, and soon the disease spread to family members and other people who were in close contact with patients. Nosocomial spread occurred only in 2 cases. A different picture of the incidence represented in the city of Maridi (Sudan) and Zaire, where the hospital played the role of a catalyst of the epidemic process. The patients were taken to hospital with a fever of unclear etiology. Nosocomial infection spread among staff was carried out when infected material (blood and excretions) hit the damaged skin and mucous membranes, patients – with various parenteral manipulations performed with insufficiently processed instruments. A survey of family contacts confirmed the epidemiological significance of contact with patients and the duration of communication with them. So, with short-term contact with the patient, 23% fell ill, and with close and long-term (patient care) 81% of the persons. Secondary foci were the families of patients who left the hospital. Infection occurred through close contact with patients (medical care, cohabitation, ritual ceremonies in the bodies of the dead). In December 1994-June 1995, an outbreak of Ebola fever occurred in Zaire, which was associated with the consumption of monkeys carrying viruses by the local people. The total number of cases exceeded 250 people, the mortality rate was about 80%. Cases of intralaboratory infection with Ebola have also been described when working with green monkeys. Given the enormous opportunities and speeds of international movements, a serious danger is the migration of persons in the initial stage of the disease and the transport of infected animals.
Pathogenesis During Ebola Haemorrhagic Fever
During the incubation period, the virus reproduces in the regional lymph nodes, spleen, and possibly other organs. Acute onset of the disease with fever coincides with the development of intense viremia with multiorgan dissemination of the pathogen. The damage to cells and tissues of various organs is presumably due to both the direct cytopathic effect of the virus and autoimmune reactions. The development of microcirculation disorders and rheological properties of blood is manifested by capillary toxicosis with hemorrhagic syndrome, perivascular edema, and DIC. Disseminated intravascular coagulation is a leading syndrome, detected histologically. Pathological changes in organs in the form of focal necrosis, scattered hemorrhages in the clinical picture show signs of hepatitis, interstitial pneumonia, pancreatitis, orchitis, etc. Cellular and humoral immunity reactions are reduced; .
Symptoms of Ebola Haemorrhagic Fever
The incubation period varies from several days to 2-3 weeks. The onset of the disease is acute, with a rise in body temperature up to 38-39 ° C, headache, myalgia and arthralgia, malaise, nausea. During the first days, most patients develop symptoms of angina; inflammation of the tonsils causes a painful “ball in the throat.” In the midst of the disease, indomitable vomiting, abdominal pain and diarrhea of a hemorrhagic character with feces in the form of melena join. The hemorrhagic syndrome develops rapidly with manifestations of skin hemorrhages, organ hemorrhages, and bloody vomiting. Often, signs of encephalopathy are observed in the form of agitation and aggressiveness of patients; in cases of recovery, they persist for a long time and during the recovery period. On the 4-6th day of the onset of the disease, approximately half of the patients have a rash of a rash nature.
The lethal outcome occurs, as a rule, at the beginning of the 2nd week of illness. Its main causes are bleeding, intoxication, hypovolemic and toxic shock shocks.
In cases of recovery, the acute phase of the disease lasts 2-3 weeks. The convalescence period is delayed up to 2-3 months, accompanied by asthenia, anorexia, weight loss, hair loss, and sometimes the development of mental disorders.
Complications can be considered all severe pathogenetic processes, leading ultimately to the death of patients: bleeding, hypovolemic and infectious toxic shocks. The prognosis of the disease is extremely unfavorable; in some foci, mortality ranges from 50% to 90%.
Diagnosis of Ebola Haemorrhagic Fever
Recognition is based on epidemiological prerequisites (stay in an endemic area, contact with patients, etc.) and characteristic clinical symptoms. Specialized laboratory tests record certain antigens and / or virus genes. Antibodies to the virus can be determined, and the virus can be isolated in cell culture. Testing of blood samples is associated with a high risk of infection and should be carried out with a maximum level of biological protection. New developments in diagnostic technology include non-penetrating methods of diagnosis (using saliva and urine samples).
Differential diagnostics presents significant difficulties due to the lack of specific clinical signs and the transience of the disease. In Ukraine, the disease can be brought from the countries of Central and West Africa.
Treatment for Ebola Haemorrhagic Fever
In certain cases, intensive care is required: in the case of dehydration, intravenous fluids and oral rehydration with solutions containing electrolytes. There is no acceptable cure or vaccine against Ebola yet. Several vaccine candidates are being tested, but it will be several more years before they become available. New drug therapy has shown promising results in laboratory studies. But it can also be available only in a few years.
Prevention of Ebola Haemorrhagic Fever
Patients with hemorrhagic fevers of Lassa, Marburg and Ebola are subject to immediate hospitalization in the box office with a strict regimen recommended in cases of especially dangerous infections, such as plague and smallpox. The recovered are discharged not earlier than the 21st day from the onset of the disease with the normalization of the condition of patients and 3-fold negative virological studies. All household items of the patient must be strictly individual, marked. They are stored and disinfected in the box. Apply single use instruments for treatment; after using them, auto-keyboard or burn. During the current disinfection period, a 2% phenol solution is used [with the addition of 0.5% sodium bicarbonate (1: 500)], iodoform (450 g per 1 ml of active iodine with the addition of 0.2% sodium nitrate). Discharge patients are also treated accordingly. Maintenance personnel should work in a Type 1 anti-plague suit. Special plastic boxes have been developed, in which with the help of an exhaust system equipped with a decontamination unit, air flow is ensured in one direction – inside the box. Such boxes are equipped with a conventional system to ensure complete safety of personnel during medical procedures. Particular caution should be observed in studies of blood and other biological materials from patients with hemorrhagic fevers and suspicious of the disease.
Persons who were in direct contact with the patient (or a person who is suspected of developing the disease) are isolated in a box and observed for 21 days. In all cases of suspected Ebola virus infection, specific immunoglobulin from the serum of hyperimmunized horses is injected. The validity of immunoglobulin – 7-10 days.