Lassa fever is an acute viral disease caused by the Lassa fever virus (LASV), which belongs to the Arenaviridae family. The main source of infection are rodents, in particular the genus Mastomys, which spread the virus through their excrement. The disease is characterized by high mortality in unvaccinated populations and is widespread in West and Central Africa. The infection can manifest itself as viral fever symptoms, including fever, myalgia, headache and gastrointestinal disorders, as well as more serious forms, such as hemorrhagic syndrome, which can manifest itself several days after infection.
History of the disease and interesting historical facts
Lassa fever was first described in 1969 in Nigeria, where fatal cases were reported among health care workers and pregnant women. The disease takes its name from the town of Lassa, where the first epidemics were recorded. Research since then has shown that the virus can be transmitted not only through contact with rodents, but also from person to person, making it even more difficult to control. The rate of transmission of the virus increased significantly in the 1970s, leading to major epidemics in Nigeria, Sierra Leone, and Guinea, among others. In recent years, attention to Lassa fever has increased due to cases associated with international travel, which have raised concerns about possible outbreaks in non-traditional areas.
Epidemiology
Lassa fever is particularly prevalent in West Africa, where tens of thousands of cases are reported each year. According to the World Health Organization, approximately 300,000 to 500,000 cases of Lassa fever occur each year, but the true incidence may be significantly higher because many patients may not receive medical care or may be misdiagnosed. The case fatality rate for the disease ranges from 11 to 15%, depending on a number of factors, including the level of medical care and the immune response of patients. Major outbreaks of the disease are more common in areas with low socioeconomic status, which facilitates the spread of infection.
Genetic predisposition to this disease
At present, the study of genetic predisposition to Lassa fever is in its early stages. By focusing on genetic factors related to the body’s ability to respond to infection, scientists have identified certain variations in genes associated with the immune response. For example, studies suggest that the interferon (IFN) specificity gene may play a role in susceptibility to the virus. However, further research is needed to identify the exact genetic markers that may predispose to a more severe course of the disease.
Risk factors for the development of this disease
Lassa fever typically affects people in settings with high viral loads and poor health care. Factors that increase the risk of infection include:
- Living and working in farming areas where rodents are common.
- Unprocessed or undercooked foods containing the virus.
- Contact with excreta of infected rodents.
- Poor healthcare waste management practices or poorly developed healthcare systems.
- Lack of strict sanitary practices in hospitals and clinics.
Diagnosis of this disease
Diagnosis of Lassa fever is based on clinical symptoms such as:
- Fever accompanied by chills and sweating.
- Myalgia and headache.
- Nausea and vomiting, sometimes with blood.
- Diarrhea.
- Respiratory symptoms including cough and respiratory distress.
- Hemorrhagic manifestations in severe cases.
Laboratory tests include PCR and serologic tests to detect the virus and antibodies. Radiological examinations may reveal changes in the lungs (atelectasis, pleurisy). Differential diagnosis with other infections such as Ebola fever and hemorrhagic syndrome caused by other viruses must be performed.
Treatment
Treatment of Lassa fever focuses on supportive care:
- Hydration and correction of electrolyte balance.
- Symptomatic treatment - antipyretic, antiviral drugs.
- If a severe form is suspected, ribavirin may be used.
- Antibiotic therapy to prevent secondary bacterial infection.
- Hospitalization in an infectious diseases department for monitoring the condition and treating complications.
Surgical treatment may be required in rare cases in the presence of hemorrhagic manifestations or thrombus formation.
List of medications used to treat this disease
- Ribavirin
- Paracetamol
- Antibiotics (eg, Ceftriaxone to prevent infections)
- Intravenous rehydration solutions (Ringer's, Sodium chloride)
Disease monitoring
Patients infected with Lassa virus are monitored through regular assessment of their condition and viral load concentration. The prognosis for most patients is good if they seek medical attention promptly; however, the virus can cause severe complications such as hepatitis and pulmonary hemorrhage, especially in immunocompromised individuals. Post-infection complications include hearing impairment and neurological disorders, which require long-term monitoring.
Age-related features of the disease
The disease can progress differently depending on the patient's age. In children and the elderly, the risk of severe disease increases significantly due to the peculiarities of the immune response. Newborns and infants often have more pronounced clinical manifestations and high mortality from infection. In adults, on the contrary, the clinical picture may be less pronounced, but there is also a risk of chronic consequences and re-infection.
Questions and Answers
- How is Lassa fever transmitted? The infection is transmitted through contact with the secretions of infected rodents, as well as from person to person through blood and biological fluids.
- What are the main symptoms of the disease? Symptoms include fever, myalgia, headache, nausea, vomiting, and hemorrhagic manifestations in severe cases.
- Is it possible to avoid infection? Basic preventive measures include maintaining good sanitation, wearing protective clothing, and responding quickly to rodent bites.
- How is Lassa fever treated? Treatment includes supportive care, use of ribavirin, and prophylaxis of secondary infections.
- What are the consequences of the disease? Consequences can range from complete recovery to serious complications such as neurological disorders and hearing impairment.
Advice from Dr. Oleg Korzhikov
Regarding Lassa fever, the attending physician Oleg Korzhikov recommends the following:
- Regularly maintain sanitary conditions in both the environment and your home to minimize exposure to rodents.
- If symptoms such as fever and myalgia occur, seek medical attention without delay, especially after travel to endemic areas.
- Use protective equipment when working with agricultural products or in open spaces to minimize the risk of infection through contact with potential carriers.
- If you experience long-term symptoms after an infection, be sure to consult a specialist for a differential diagnosis and recommendations for rehabilitation.
