Lassa fever is an infectious disease that belongs to the group of hemorrhagic fevers and is caused by a Lassa virus. It is highly contagious and distinguishes by gradual development, severe intoxication, hemorrhagic syndrome and liver damage. The disease is widely spread in some countries of Western and Central Africa.
The incubation period that lasts from the moment of infection until the first symptoms of the disease are 7-10 days on average but can be either shortened to 3 days or extended to 20 days.
Lassa fever, unlike highly contagious Ebola and Marburg fever, begins gradually. Patients experience symptoms of a toxic syndrome (fatigue, weakness, fatigue, muscle pain, headache) that are accompanied by a slight increase of body temperature (up to 38 degrees). The temperature increases slowly during 3-5 days and then reaches its maximum of 40 degrees. The fever lasts for 2 weeks, sometimes longer. Antibiotics are ineffective on this stage. The temperature fluctuations are typical for Lassa fever, i.e. a significant temperature rise is observed till the evening with a relative relief from the morning till midday. During 5 days the patients feel extremely tired, frequently the weakness is so severe that it is difficult for them to get out of bed. Redness of the face, neck and upper chest are perfectly seen during a visual examination of the patient’s condition.
Lassa fever affects several groups of lymph nodes. Lymph nodes are slightly increased in size and painful. They are not connected to each other and the surrounding tissue and the skin above them are not changed.
A sore throat is one of the symptoms typical for most patients with Lassa fever. This symptom appears on the 3-4th day of the disease and is characterized by the pain during swallowing and dry mouth. Redness of the throat that has clear boundaries and increased tonsils are also observed.
Gastroenteritis is another frequent symptom of Lassa fever. Patients complain of nausea, vomiting and stomach pain. Severe course the disease may provoke dehydration, the first signs of which are thirst, dry mouth, bluish skin, low blood pressure, reduced urine output and convulsive twitching of muscles.
By the end of the first week, symptoms of the hemorrhagic syndrome, namely a hemorrhagic rash on the body may appear.
If the course of the disease is very severe, the above symptoms are complemented by the following complications:
pneumonia and pulmonary edema that are manifested by a cough, pain in the chest during a cough and breathing; X-ray examination reveals infiltrative changes;
toxic damage of the myocardium;
toxic damage of the liver (increased liver size, pain in a right part of the belly, changes of the laboratory parameters);
toxic damage of kidney that provokes an acute renal failure;
toxic shock ( rapid fall of the blood pressure, bluish skin, and reduced urine output);
toxic encephalopathy, i.e. swelling of the brain;
severe manifestations of the hemorrhagic syndrome (intestinal or uterine bleeding, bleeding in the adrenal glands, myocardium, and brain).
Each separate complication may lead to the patient’s death if the course of the Lassa fever is severe. The lethal outcome occurs on the 7-14th day since the onset of the disease in 40% of the patients on average. In case of a favorable outcome, the symptoms may remain for 3-4 weeks. If the patients recover, they may still experience a slight temperature rise and fatigue or weakness during 8-12 days.