Lassa Fever - Causes, Symptoms, Diagnosis, and Treatment

Introduction

Lassa fever is an acute hemorrhagic disease that is endemic in the rodent population of West Africa. It is endemic in Guinea, Mali, Ghana, Togo, Benin, Sierra Leone, Liberia, and Nigeria. Although 8 out of 10 people with the disease do not show symptoms, estimates show that every year 100,000 to 300,000 cases of the disease are reported in West Africa, along with around 5000 deaths due to the illness. International travel has led to a few cases in Germany, the United States, the United Kingdom, and Sweden; hence international travel to these endemic countries is restricted during the outbreaks. The outbreaks may be seen any time around the year but are more prevalent from February to late March.

What Is Lassa Fever?

Lassa fever is a viral hemorrhagic disease. It is a zoonotic disease and is spread by multimammate rats. It is an acute febrile illness that lasts for one to four weeks. The first case of Lassa of fever was reported in 1969, when two missionary nurses died in Lassa village in Nigeria due to the illness, from where it gets its name.

What Causes Lassa Fever?

Lassa fever is caused by the Lassa virus, a single-stranded RNA (ribonucleic acid) virus that belongs to the Arenaviridae family. The African multimammate rats are believed to be the reservoirs of the Lassa virus, especially Mastomys natalensis, Mastomys erythroleucus, and Hylomyscus pamfi. Humans acquire the disease due to food contamination with rat urine, saliva, or feces.

How Does Lassa Fever Spread?

Lassa fever is an animal-borne disease and is spread by multimammate rats. The Lassa virus hosts within the body of these rats and spreads quickly as the rats breed rapidly. Humans get the illness when:

• They accidentally touch the rat's urine, saliva, or droppings and eat food.

• The rats live in the place where people store food and contaminate the food.

• They cook rodents as food.

• They breathe in droplets containing the feces of the rat.

• Open sores or cuts get contaminated with rat droppings.

It is contagious and can spread if an individual is exposed to the infected person's urine, feces, saliva, blood, or vomit but not through touch. It may also happen through blood and body fluid transfusion and contaminated medical equipment, like reused syringes. However, experts believe the disease is contagious only after the symptoms appear.

What Are the Signs and Symptoms of Lassa Fever?

The symptoms of Lassa fever generally appear 6 to 21 days after the infection. Estimates show that 8 out of 10 people with the disease do not show any symptoms; however, they may experience a general malaise, fever, and headache. The rest 20 percent may experience severe symptoms, including:

• Bleeding gums.

• Breathing difficulty.

• Cough.

• Bleeding from the nose and eyes.

• Vomiting with blood.

• Swelling of the face.

• Difficulty swallowing.

• Hepatitis.

• Chest pain.

• Back pain

• Diarrhea with blood.

• Shock.

• Hearing loss.

• Abdominal pain.

• Abnormal heart rhythm.

• High or low blood pressure.

• Pericarditis.

• Encephalitis.

• Tremors.

• Seizures.

• Meningitis.

In one percent of the cases, the illness could be fatal. Death may occur within two weeks after the symptoms appear because of organ failure.

What Are the Complications of Lassa Fever?

Permanent deafness due to the disease is the most common complication. The severity of the illness does not affect deafness; it may develop in mild and severe cases. However, many degrees of deafness may be seen in one-third of the infected population, and many patients may have permanent hearing loss.

Death is another complication in 10 to 20 percent of hospitalized patients for Lassa fever, although only one percent of all Lassa virus infections are fatal. Pregnant women in their third trimester are particularly prone to severe conditions, including death. Spontaneous abortion is a severe illness complication estimated to cause 95 percent mortality in fetuses.

How Is Lassa Fever Diagnosed?

Since the symptoms of Lassa fever are non-specific and so varied, clinical diagnosis of the disease is difficult. However, specialized laboratory tests can help diagnose the test:

• ELISA (enzyme-linked immunosorbent serologic assay) can help detect the presence of IgM and IgG antibodies and Lassa antigens.

• RT-PCR (reverse transcriptase-polymerase chain reaction) can be used in the early stages of the illness.

• Tissue specimens can be used to perform immunohistochemistry stains.

What Is the Treatment for Lassa Fever?

Lassa fever is treated with antiviral medications called Ribavirin. The drug is known to be most effective in the early stages of the illness. It can be taken intravenously or as a pill. In case of a severe infection, hospitalization and supportive care consisting of maintaining the blood pressure, oxygen level, and the appropriate fluid and electrolyte balance is required.

How Can Lassa Fever Be Prevented?

There is no vaccine for Lassa fever; it is recommended to prevent the rodents that spread the infection and prevent illness. However, after the outbreak in 2018, the WHO (World Health Organization) and many public health entities are working on developing an effective vaccine.

Measures to prevent the illness include:

• Avoid contact with the Mastomys rats.

• Avoid traveling to places with Lassa fever outbreaks.

• Keep food in rodent-proof enclosures.

• Keep the house and the surrounding area clean not to attract rodents.

• Keep rat traps in the home if the place is rodent-infested.

• Wear gloves or protective gear when handling rat traps and cleaning up after rodents.

• Close holes and spaces around the house where a rat can habitat.

• Keep the garbage bins away from home.

• Do not use rodents as a food source.

• Wear protective clothing and gear, including face masks and gloves, when caring for an infected person.

• Isolate infected patients to avoid the spread.

• Maintaining hand hygiene by washing hands regularly.

• Educate people in high-risk areas about measures to reduce the rodent population in their homes.

Conclusion

Lassa fever is an acute hemorrhagic fever spread by rodents. It is an endemic illness in parts of West Africa. Although 80 percent of the infected people do not show symptoms, 20 percent may have severe symptoms, including bleeding from the mouth, nose, and eyes. The disease is especially severe for pregnant women, with 95 percent mortality in fetuses. However, it can be treated with Ribavirin, which is most effective in the early stages of the infection. In addition, preventing rodent infestations in the house can help avoid this illness to a significant extent.