Lassa fever is a disease that belongs to the group of hemorrhagic viral infections. As a result, the kidneys are affected, the liver is destroyed, and an extensive fever develops. The disease is characterized by acute capillary toxicosis, when superficial vessels are damaged along with the skin, their permeability increases dramatically. A very life-threatening disease, death is observed in 40% of cases. Half a million people get Lassa fever every year. The disease lasts for two weeks, women in the second half of pregnancy are especially difficult to tolerate fever, in which case the mortality rate is about 80%.
Geographical areas of disease distribution
In 1969, Nigerian scientists detect a fever among the inhabitants of the town of Lassa, researchers and nurses are exposed to the disease. Of the first five cases, three led to the death of patients. Microbiologists identify the pathogen in a year. By this time, Lassa fever covers countries in West Africa, such as: Guinea, Mali, Nigeria, Senegal, etc. The central parts of the African continent do not lag behind in terms of the epidemiological threshold. Sometimes foci occur in European countries,Israel, USA, Japan, where the causative agent of the virus is carried by traveling citizens.
Description of the causative agent of fever
The causative agent of Lassa fever is a member of the RNA genomic viral family that does not have DNA, and the genetic information is encoded in one or two RNA strands. The structure coincides with the design of the Bolivian and Argentine fever virus, the causative agent of choriomeningitis. The diameter of the viral virion is only 80-160 nm, it is enclosed in a round lipid membrane, the surface of which is covered with villi. Examination under a microscope reveals a dozen ribosomes inside the virus particle, which are dense small granules.
Due to the presence of internal particles similar to grains of sand, the virus is called Arenavirus from the family Arenaviridae (in Latin, arenaceus means sandy). Over the past decade, scientists have identified 4 subgroups that are Lassa fever and are spreading in various areas of Africa. The resistance of the virus to changes in the surrounding space lies in the fact that its ability to live when it enters the blood or body secrets does not disappear for a long time. To reduce its activity, chloroform and ether are used.
Sources and carriers of the virus
Carriers of the virus are considered to be multi-nipple rats of the African continent, the species Mastomys natalensis. In epidemiologically dangerous areas, the number of infected individuals is 14-18% of the total number of rats, and an infected rodent carries the virus for life, sometimes without manifestationsymptoms of the disease. The source of infection is also a sick person, all body fluids of which are contagious to others.
The conditions for contracting Lassa fever are the transmission of infection through the air with droplets of liquid when coughing, sneezing, breathing. The infection is found in the faeces and urine of rats, which can get on food and human skin. Infection in infected areas occurs through inhalation of air sprayed with the smallest animal excrement, use of moisture from a source of water contaminated with viruses, and undercooked rat meat, commonly eaten.
Rodents transmit the virus between themselves through contact, drinking, feeding, reproduction. From the patient, another person becomes infected by contact methods and sexually. A pregnant mother transmits the virus to the baby's body. The staff of the infectious diseases clinic picks up the disease during procedures with blood and during surgical intervention, autopsy, servicing patients with severe catarrhal manifestations. In the blood of all patients who have had the disease, Lassa fever leaves antibodies that persist for up to 7 years, which can be detected in a laboratory study.
Epidemiological situation
The disease is referred to as focal viral fevers. People in western Africa are most at risk. Infection is equally likely in the countryside as in the city, due to the large population of polynylon rats. More than half of cases end in death.
The emergence of immunity to a recurring disease is little studied, but suchcases of infection sometimes occur, while repeated treatment and prevention of Lassa fever does not require significant efforts, the disease proceeds easily. In almost all parts of Africa, the infection is ascertained all year round, but the largest outbreaks occur in the cold season, when hordes of rats move closer to people's homes.
Cases of the virus moving to the countries of the European continent take place, but to prevent such a spread, all those with a fever are subject to strict accounting on an international scale. Males and females are equally at risk of infection. The virus spreads most intensively in places with poor sanitation, densely populated areas of the poor.
Pathogenesis of disease
The mucous membranes of the human body are a kind of gateway for infection to enter the body. The virus for the passage of the incubation period is localized in the lymph nodes, at the end of the stage, an acute febrile period begins with the spread of particles throughout all body systems. Cells of vital organs containing the virus take on the destructive effect of cytotoxic lymphocytes, Lassa fever appears. Symptoms and treatment of the disease are of increasing interest to specialists. In the course of the disease, necrosis of the liver and kidneys, destruction of the spleen and heart muscle develops.
The severity of the course of the disease depends on the body's immunity, so the lethal outcome is predetermined by a violation of cellular reactions. When a febrile period of the disease occurs, the formation of antibodiesto destroy viruses, it is suspended and has a delayed course - this is how Lassa fever manifests itself. A photo of the patient is shown below.
Lassa disease symptoms
The incubation period lasts from a week to three, then the acute period of the disease begins, accompanied by characteristic symptoms:
- febrile condition begins with a slight increase in body temperature;
- general malaise, feeling of weakness;
- myalgia occurs, pain in the larynx when swallowing;
- eyes affected by conjunctivitis;
- when body temperature rises to chills, general weakness increases;
- there are severe pains in the back, abdomen, chest;
- sometimes there is nausea, diarrhea, convulsions;
- severe cough turns into vomiting;
- violated visual perception of the surrounding space.
Patient examination
Always on examination there is swelling of the neck and face, chest area, hemorrhagic effects occur in different areas, palpation shows a large increase in lymph nodes. Examination of the larynx reveals ulcers, the mucosa is characterized by the appearance of white spots, precursors of subsequent ulcers that Lassa fever gives. Symptoms on examination of the heart are muffled tones, severe bradycardia, and an increase or decrease in blood pressure. With the further course of the disease, myocarditis develops, and bradycardia is replaced by tachycardia.
Examination for suspected disease reveals on the skinthe patient has numerous hemorrhages, in addition to them, spots, papules, roseola appear, sometimes the rash in nature resembles a manifestation of measles. The heart is enlarged, the patient is worried about shortness of breath, cough, wheezing in the lungs of a wet or dry nature. The internal areas of the peritoneum make themselves felt with pain, rumbling in the abdomen, and diarrhea. On examination, the liver was enlarged. Lassa fever also manifests itself as disorders of the nervous system. Epidemiology notes cases of loss of consciousness, hearing, tinnitus, there is complete or partial baldness of the head.
Laboratory blood tests reveal leukopenia, then leukocytosis, while the leukocyte formula shifts to the left, an increased platelet count and a decrease in prothrombin levels are characteristic, an increase in ESR to 50-80 mm / h. Blood clotting decreases, an increase in the prothrombin period is observed. Kidney failure makes itself felt by an increased content of urea in the blood, a study of the patient's urine reveals proteinuria and cylindruria. Urine contains leukocytes, erythrocytes, protein impurities, granular casts.
Since Lassa fever refers to focal natural diseases, if a virus is suspected, an epidemiological history is taken, prerequisites for the manifestation of the disease are identified due to the patient's stay in an infected area. X-ray, FDSG, ultrasound, MRI of disturbed organs and body systems are used as instrumental studies. To determine the disease, patients seek advice from a pulmonologist, cardiologist, neuropathologist, gastroenterologist.
Severe course and complications
In 37-52% of cases, the severity of the disease leads to severe damage to the lungs (pneumonia of varying severity), heart (myocarditis), liver (cirrhosis), kidneys (failure). Severe swelling of the pleural areas of the body manifests Lassa fever. Epidemiology, clinic, prevention do not always give positive forecasts and have a curative effect. More than half of the cases predict the death of the patient after two weeks from the onset of the disease. The favorable course of the disease lasts from 3 weeks, then the temperature begins to decrease. Recovery is slow, with symptoms recurring and occasional relapses.
Differentiation of diagnosis from other diseases
In many symptoms, the manifestation of the disease is similar to hemorrhagic fevers of other types. Typhus fever, dengue fever, yellow fever, Kyasanur forest disease, West Nile fever, Chikungunya, tropical malaria, scarlet fever, meningitis resembles Lassa fever. Marburg, Ebola also on the grounds have much in common and should be excluded from suspected diseases.
Malaria is similar to the symptoms of Lass in that in both diseases there is high body temperature, headaches, yellowing of the skin. The difference lies in the fact that malaria is not characterized by the appearance of necrotic ulcers in the larynx and a large increase in lymph nodes, hemorrhagic syndrome rarely develops. In addition, malaria is characterized by pale skin, excessive sweatingand uneven manifestation of fever, focal rashes.
Hemorrhagic fever with renal syndrome is characterized by common symptoms with Lassa disease, manifested by headaches and muscle cramps, scleritis, conjunctivitis, oliguria. But HFRS does not cause repeated vomiting, ulcerative pharyngitis and diarrhea in a person. Unlike Lass disease, from the first day of the course of this disease, dry mouth occurs, intense thirst and severe muscle weakness.
Leptospirosis is characterized by similar symptoms in the form of fever, headaches, myalgia, conjunctivitis, scleritis, oliguria. But the absence of necrotic ulcers in the mouth in leptospirosis distinguishes it from Lassa fever disease. With leptospirosis, there is no cough, diarrhea, vomiting, there are no chest pains, leukopenia, bradycardia are not detected in laboratory tests. Lassa fever has completely different symptoms. A photo of those affected by the disease is presented below.
Acute viral Marburg fever resolves with severe symptoms, with Lassa-like symptoms. It is characterized by a high degree of lethal outcomes, the development of a febrile state, hemorrhagic syndrome, severe damage to internal organs and the central nervous system. The source of infection has not been precisely established, it is assumed that the virus is transmitted to humans from green monkeys by droplets or air, as well as by contact with an animal.
Healing methods
All patients with suspected infection are subject to mandatory hospitalization in special clinics. When keeping the patient on treatment, a strict isolation regime is observed without the slightest violations. A horizontal bed position is prescribed, loads are excluded, the treatment is aimed at eliminating the emerging symptoms of the disease. In the first weeks, the causes are determined, and the treatment of Lassa fever primarily consists in the use of convalescent plasma. This is effective only at the beginning of the disease, since the use of the drug during a prolonged course of fever in some cases provokes a worsening of the disease and the development of complications.
Complication of the disease is treated with strong antibiotics and glucocorticoids. In the modern medical pharmaceutical business, new etiotropic drugs and vaccines have been developed. The use of Virazole, Ribamidil, and Ribavirin in the treatment of drugs remains effective today. They are taken orally in the initial stage of the disease, in the amount of 1000 units per day. Reception is not stopped within 10 days. It is enough to inject the drug intravenously for 4 days, which helps to improve the course of the disease and reduce the mortality rate.
Disease prevention
Too much loss of human life is caused by Lassa fever. Disease prevention is of paramount importance in epidemiologically hazardous areas. In order to prevent the penetration of the virus into human habitation, it is necessary to stop the access to it of multi-jawed rats and rodents of other species. Usually food and freshwater wellsdrinking water is carefully covered to prevent urine and rodent excrement from getting into them. As a preventive measure, rats are poisoned everywhere, followed by the burning of carcasses.
Great preventive importance is given to raising the standard of living of the indigenous African population, improving the quality of nutrition for the emergence of sufficient immune protection of the body. Talks and lectures are held to improve the cultural and living standards, the need to comply with individual sanitary standards for each person is explained.
Doctors and other medical personnel of infectious diseases clinics are provided with the necessary personal prevention equipment, such as gloves and masks for patient care. Local doctors and doctors sent to the epidemiologically dangerous area are being trained for the correct and safe conduct of the evacuation and ensuring the anti-epidemic regime.
Events in the epicenter of the epidemic
Systematic quarantine actions are sure to take place if Lassa fever occurs in any area. Anti-epidemic measures are being taken urgently without delay. They are aimed at organizing strict quarantine with complete isolation of patients in infectious boxes, warning the local population about the beginning of the epidemic. All personnel involved are required to wear anti-plague suits and personal protective equipment.
Required ishospitalization of persons suspected of being in contact with sick people, burning of things and household items of sick and contact people that have no material value, burning in the crematorium of the bodies of those who died from the disease, disinfection in rooms and houses. Persons who have arrived in "clean" areas from the places where the epidemic is spreading are isolated in stationary institutions if there is the slightest suspicion of the onset of the disease.
In conclusion, it should be noted that the fatal fever recedes if safety measures are strictly implemented, effective measures are taken to reduce the risk of the disease, and treatment is started in a timely manner.
