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 extensive fever develops. The disease is characterized by acute capillary toxicosis, when along with the skin surface vessels are damaged, their permeability sharply increases. A very life-threatening disease, death is observed in 40% of cases. Every year, half a million people get Lassa fever. The disease proceeds within two weeks, the woman's fever is especially difficult to tolerate in the second half of pregnancy, in this case the mortality rate is about 80%.
Geographical areas of the spread of the disease
In 1969, Nigerian scientists determine the fever in the inhabitants of the town of Lassa, researchers and nursing nurses are exposed to the disease. Of the first five cases, three led to the death of patients. Microbiologists in a year identify the pathogen. Lassa fever by this time 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, the 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 representative of the RNA genomic viral family that does not have DNA, and genetic information is encoded in one or two RNA chains. The structure coincides with the construction 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 circular lipid membrane, the surface of which is covered with villi. Examination under a microscope reveals a dozen ribosomes inside the viral 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 Arenaviridae family (in Latin arenaceus stands for sandy). Over the past decade, scientists have identified 4 subgroups, which are Lassa fever and spreading in various regions of Africa. The resistance of the virus to changes in the surrounding space is that its ability to function when it enters the bloodstream or body secrets does not disappear for a long time. To reduce its activity, chloroform and ether are used.
Sources and peddlers of the virus
The carriers of the virus are considered to be multisucking rats of the African continent, a species of Mastomys natalensis. In epidemiological hazardous areas, the number of infected individuals is 14-18% of the total number of rats, and the infected rodent carries the virus for life, sometimes without the manifestation of symptoms of the disease. The source of infection is also a sick person, all body fluids of which are infectious to others.
The conditions for Lassa fever are airborne infections with droplets of fluid during coughing, sneezing, and breathing. The infection is found in the feces and urine of rats, which can get on food and human skin. Infection in infected areas occurs by inhalation of air with the smallest excrement of animals, the use of moisture from a source of water contaminated with viruses and insufficiently cooked rat meat, commonly eaten.
Between themselves, rodents transmit the virus upon contact, drinking, feeding, reproduction. From the patient, another person becomes infected by contact methods and sexually. A pregnant mother passes the virus to the baby’s body. The staff of the infectious diseases hospital picks up the disease during blood procedures and during surgical intervention, opening the bodies, servicing patients with severe catarrhal manifestations. In the blood of all patients who have had the disease, Lassa fever leaves antibodies that last up to 7 years, which can be detected in a laboratory study.
Epidemiological situation
The disease is classified as focal viral fever. Residents of western Africa are most at risk. Infection is equally likely both in the village and in the city, due to the large population of multisig rats. More than half of cases end in death.
The emergence of immunity to a recurring disease has been little studied, but such cases of infection are sometimes found, while re-treatment and prevention of Lassa fever does not require significant effort, the disease proceeds easily. In almost all areas of Africa, infection has been reported year-round, but the largest outbreaks occur during the cold season, when hordes of rats migrate closer to human housing.
Cases of the movement of the virus to countries of the European continent take place, but to prevent this spread, all patients with fever must be strictly accounted for internationally. Male and female persons are equally at risk of infection. The virus spreads most intensively in places with poor sanitary conditions, in densely populated areas of the poor.
Pathogenesis of the disease
The mucous membranes of the human body are a kind of gateway for infection in the body. The virus for 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 among specialists. During the disease, necrosis of the liver and kidneys, destruction of the spleen and heart muscle develop.
The severity of the course of the disease depends on the immunity of the body, so the lethal outcome is predetermined by a violation of cellular reactions. When a febrile period of the disease occurs, the formation of antibodies to kill the viruses stops and has a delayed course - this is how Lassa fever manifests itself. A photo of the patient is presented below.
Symptoms of Lass disease
The incubation period lasts from a week to three, then an acute period of the disease begins, accompanied by characteristic symptoms:
- fever begins with a slight increase in body temperature;
- general malaise, a feeling of weakness;
- myalgia, pain in the larynx when swallowing;
- eyes are affected by conjunctivitis;
- with an increase in body temperature to chills, general weakness intensifies;
- severe pain in the back, stomach, chest;
- nausea, diarrhea, cramps are sometimes observed;
- severe cough turns into vomiting;
- disturbed visual perception of the surrounding space.
Patient examination
On examination, there is always swelling of the neck and face, chest area, hemorrhagic effects occur in different areas, with palpation there is a large increase in lymph nodes. Examination of the larynx reveals ulcers, the appearance of white spots on the mucous membrane, the precursors of subsequent ulcers, which gives Lassa fever. Symptoms during the examination of the heart appear in 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 with a suspected disease reveals numerous hemorrhages on the patient’s skin, in addition to them, spots, papules, roseola appear, sometimes the rash in nature resembles the manifestation of measles. The heart is enlarged, the patient is concerned 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, diarrhea. Examination of the enlarged liver. Lassa fever also manifests itself as a disorder of the nervous system. Epidemiology notes cases of loss of consciousness, hearing, tinnitus, complete or partial baldness of the head is observed.
Laboratory blood tests reveal leukopenia, then leukocytosis, while the leukocyte formula shifts to the left, characterized by an increased platelet count and a decrease in prothrombin, an increase in ESR to 50-80 mm / h. Blood coagulation decreases, an increase in the prothrombin period is observed. Kidney insufficiency makes itself felt with an increased content of urea in the blood, a study of the patient's urine reveals proteinuria and cylindruria. Urine contains white blood cells, red blood cells, protein impurities, granular cylinders.
Since Lassa fever is a focal natural disease, when an infection is suspected, an epidemiological history is carried out, the prerequisites for the manifestation of the disease due to the patient's stay in the infected area are identified. As instrumental studies, X-rays, FDSG, ultrasound, MRI of disturbed organs and systems of the body are used. On questions of determining the disease, patients seek advice from a pulmonologist, cardiologist, neurologist, 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 edema of the pleural regions of the body manifests Lassa fever. Epidemiology, clinic, prevention do not always give positive forecasts and have a healing effect. More than half of cases predict the death of a 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, symptoms reappear, relapses occur from time to time.
Differentiation of the diagnosis with other diseases
For many symptoms, the manifestation of the disease is similar to other types of hemorrhagic fevers. Typhus fever, Dengue fever, yellow fever, Kyasanur forest disease, West Nile fever, Chikungunya, tropic malaria, scarlet fever, meningitis resembles Lassa fever. Marburg, Ebola also have a lot in common and should be excluded from suspected diseases.
Malaria is similar to the symptoms of Lassa in that with both diseases, high body temperature, headaches, and yellowing of the skin are observed. The difference is 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 pallor of the skin, excessive sweating and uneven manifestation of fever, focal rashes.
Hemorrhagic fever with renal syndrome is characterized by common symptoms with Lass disease, manifested by headaches and muscle cramps, scleritis, conjunctivitis, oliguria. But HFRS does not cause a person to repeatedly vomit, ulcerative pharyngitis and diarrhea. Unlike Lass disease, from the first day of the course of this disease, dry mouth, severe thirst and sharp muscle weakness occur.
For leptospirosis, similar symptoms are characteristic in the form of a fever, headaches, myalgia, conjunctivitis, scleritis, oliguria. But the absence of necrotic ulcers in the mouth during leptospirosis distinguishes it from the disease of Lassa fever. With leptospirosis, there is no cough, diarrhea, vomiting, there are no chest pains, leukopenia, bradycardia are not detected in laboratory studies. Lassa fever has completely different symptoms. A photo of those affected by the disease is presented below.
Acute viral fever Marburg goes away with severe symptoms, symptoms similar to Lass disease are observed. It is characterized by a high degree of fatal outcomes, the development of a febrile state, hemorrhagic syndrome, severe damage to the internal organs and 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 the drop or air method, as well as through contact with the animal.
Healing methods
All patients with suspected infection are subject to mandatory hospitalization in special clinics. When the patient is kept on treatment, a strict isolation regimen is observed without the slightest disturbance. A horizontal bed position is prescribed, loads are excluded, 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 is primarily the use of plasma reconvalescents. This is effective only at the beginning of the disease, since the use of the drug for a long course of fever provokes in some cases worsening of the disease and the development of complications.
Complications of the disease are treated with strong antibiotics and glucocorticoids. In the modern medical pharmaceutical business, new etiotropic drugs and vaccines have been developed. Effective today remains the use of virazole, ribamidil, ribavirin in the treatment of drugs. They are taken at the initial stage of the disease orally, in the amount of 1000 units per day. Reception does not stop within 10 days. Intravenously, it is enough to administer the medicine 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 epidemiological hazardous areas. In order to prevent the virus from entering the human housing, access to it should be made of multisig rats and other rodents. Typically, food and fresh drinking water wells are carefully covered to prevent urine and rodent excrement from entering them. As a prophylaxis, rats are poisoned everywhere with subsequent burning of carcasses.
Great preventive value is given to improving the living standards of the indigenous African population, improving the quality of nutrition for the emergence of sufficient immune defense of the body. Conversations and lectures are held to improve the cultural and everyday level, the need for observing individual sanitary standards for each person is explained.
Doctors and other medical personnel of infectious disease clinics are provided with the necessary personal preventive measures, such as gloves and masks for patient care. Doctors and local doctors who are sent to the epidemiological hazardous area are trained to properly and safely conduct evacuation and ensure an anti-epidemic regime.
Carrying out activities in the outbreak
Systematized quarantine actions must take place if Lassa fever occurs in any area. Anti-epidemic measures are carried out urgently without delay. They are aimed at organizing strict quarantine with the complete isolation of patients in infectious boxes, warning the local population about the beginning of the epidemic. All personnel involved must wear anti-plague suits and personal protective equipment.
Mandatory is the hospitalization of persons suspected of having contact with the sick, the burning of material and household items of sick and contact people, burning in the crematorium of the bodies of those who died from the disease, and disinfection of the premises and houses. Persons arriving in “clean” areas from epidemic spreading places are isolated in inpatient facilities when there is the slightest suspicion of a disease.
In conclusion, it should be noted that mortal 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.