About Lassa Fever

Overview

Lassa fever is an acute and often fatal viral hemorrhagic (bleeding) disease caused by the Lassa virus (LASV), which belongs to the Arenaviridae family. It is common in parts of West Africa, particularly Nigeria, Sierra Leone, Guinea, Liberia, and Mali. The disease was first identified in the 1950s and is primarily transmitted through contact with infected rodents, specifically the multimammate rat Mastomys natalensis. Humans can become infected by ingesting food or materials contaminated with the feces or urine of infected rodents. Person-to-person transmission can also occur, particularly in healthcare settings or within households caring for sick relatives. Lassa fever presents with symptoms such as fever, headache, sore throat, muscle pain, chest pain, nausea, vomiting, diarrhea, and abdominal pain. In severe cases, it can progress to mucosal bleeding, organ dysfunction, neurological manifestations, and death. The incubation period ranges from 5 to 21 days.

Causes and Risk Factors

Lassa fever is caused by a virus belonging to the virus family Arenaviridae. Lassa fever can be transmitted to humans through direct contact with the feces, urine, or body fluids of the multimammate rat, Mastomys natalensis, which serves as the reservoir for the Lassa virus, meaning the virus lives and spreads in these rats without making them sick. It can also spread from person to person through contact with infected individuals.

Non-modifiable risk factors for Lassa fever cannot be changed or controlled. These include:

• Age: Increasing age is a non-modifiable risk factor for Lassa fever.
• Genetic predispositions: A positive family history of Lassa fever can increase the risk.

Modifiable risk factors for Lassa fever can be influenced or changed. These include:

• Poor hygiene practices: Contact with rats, their feces, blood, or urine due to inadequate hygiene increases the risk.
• Occupational exposure: Certain occupations that involve contact with rodents or infected humans without proper infection prevention and control measures can increase the risk.
• Living conditions: Crowded living conditions and poor housing increase the chances of exposure to rodents and their body fluids.
• Farming practices: Bush burning and deforestation during the dry season can displace rodents from their natural habitats, increasing the chances of infiltration into residential areas.
• Lassa fever is more common in societies where the virus-carrying rodent is part of the human diet, as handling or consuming these animals can lead to infection.

It's important to note that these risk factors are based on available information and may not be exhaustive. It's always recommended to consult with healthcare professionals for personalized advice.

Symptoms

Common early symptoms of Lassa fever include:

• Slight fever
• General malaise and weakness
• Headache

As the disease progresses or reaches a higher severity, the following symptoms may occur:

• Bleeding (hemorrhaging) in gums, eyes, or nose
• Respiratory distress
• Repeated vomiting
• Facial swelling
• Pain in the chest, back, and abdomen
• Shock
• Neurological problems such as hearing loss, tremors, and encephalitis (inflammation of the brain)

Some cases of Lassa fever have mild symptoms and may go undiagnosed. However, in some cases the disease can progress to more serious symptoms. Deafness is a common complication of Lassa fever. Severity of the disease does not affect the likelihood of developing deafness. It's crucial to seek medical attention if you experience any concerning symptoms or suspect Lassa fever.

Diagnosis

To diagnose Lassa fever, the following examinations, tests, and procedures are commonly performed:

• Physical exam: A healthcare professional will look for fever, signs of bleeding, dehydration, and swollen lymph nodes to identify Lassa fever.
• Isolation of LASV in the blood: This test finds the Lassa virus in a blood sample.
• Detection of LASV antigen (Ag): This test identifies specific proteins from the Lassa virus in the blood.
• Detection of LASV genomic RNA: This test looks for the virus’s genetic material in the blood.
• Detection of LASV-specific antibodies: This test checks for antibodies made by the immune system in response to Lassa virus infection.

Additional examinations, tests, and procedures may be performed, including:

• Ophthalmic examination: This checks for any eye-related complications, such as retinal hemorrhages or swelling, which can occur in severe cases of Lassa fever.
• Laboratory investigations: Blood tests may be done to check for abnormalities such as liver or kidney dysfunction that could indicate disease progression.

Treatment Options

The goals of treatment for Lassa fever include:

• Rapidly detecting suspected cases to prevent further spread of the virus and ensuring timely entry into care
• Providing supportive care to maintain fluid and electrolyte balance, oxygenation, blood pressure, and treating any other complicating infections
• Administering antiviral medication, such as ribavirin, which has shown success in treating Lassa fever when given early in the course of the illness

Antiviral medication (ribavirin) works by inhibiting the replication of the Lassa virus, reducing its spread within the body. Supportive care helps manage symptoms and complications while the body fights the infection.

It is crucial to note that these recommendations are based on limited evidence and more research is needed to develop effective therapeutics and vaccines for Lassa fever. Consultation with healthcare professionals is essential for individualized treatment plans.

Medication dosing may be affected by many factors. Check with your health care professional about dosing for your individual situation. Side effects can occur. Check with your health care professional or read the information provided with your medication for side effect information.