How Does Lassa Fever Present Itself?

Lassa fever is a viral illness that occurs in West African countries like Nigeria. It is caused by the Lassa virus in a rodent of the genus Mastomys known as a “multimammate rat”. The Lassa virus is transmitted to humans mainly through food or household items contaminated by infected rats’ urine and faeces and by handling infected rats.

Lassa fever usually begins with a flu-like illness and other symptoms such as:

• Sore throat
• Severe headache
• Chest pain (especially behind the breastbone)
• Back pain
• Ringing ears,
• Nausea
• Vomiting
• Abdominal pain
• Diarrhea 

Hemorrhage is not common in less serious diseases, but the loss of fluid from blood vessels into tissue may occur; this causes facial swelling, reddened whites of the eyes, and fluid around the lungs and heart, but bleeding from the mucus membrane occurs in severe illness.

• Dry cough and respiratory distress may occur if the illness involves fluid in the lungs
• Severe disease may cause encephalitis with confusion, tremors, seizures, and coma
• Organ failure and shock are often end-stage events
• Lassa virus infects all tissues, but infection of the liver is especially typical. Hepatitis may be mild or severe, and laboratory tests may not reflect the level of injury

In around 1 percent of all cases, Lassa fever is fatal, and around 15 to 20 percent of all hospitalizations for the disease will end in death. Death can occur within 2 weeks after the onset of symptoms due to multiple organ failure.

One of the most common complications of Lassa fever is hearing loss, which occurs in around 1 in 3 infections. This hearing loss varies in degree and is not necessarily related to the severity of the symptoms. Deafness caused by Lassa fever can be permanent and total.

Finally, it is particularly dangerous for women in their third trimester of pregnancy. Spontaneous loss of pregnancy occurs in around 95 percent of pregnancies.

Investigation of Lassa Fever

According to the World Health Organization (WHO), the symptoms of Lassa fever are so varied and non-specific, that clinically diagnosing Lassa fever early can often be difficult because it may be difficult to distinguish it from other viral haemorrhagic fevers such as Ebola virus diseases, as well as other diseases that cause fever, malaise, typhoid fever, and yellow fever.

Definitive diagnosis requires testing that is available only in reference laboratories. Laboratory specimens may be hazardous and must be handled with extreme care. Lassa virus infections can only be diagnosed definitively in the laboratory using the following tests:

• reverse transcriptase polymerase chain reaction (RT-PCR) assay
• antibody enzyme-linked immunosorbent assay (ELISA)
• antigen detection tests
• virus isolation by cell culture

This is why Lassa fever should be suspected in individuals in Nigeria especially endemic areas that have been identified who show typical symptoms. And such cases should be reported to the nearest medical centers in charge of the Lassa fever virus (centers such as the Federal Medical Centre, Owo, Ondo State; Irrua Specialist Teaching Hospital, Irrua, Edo State; and Lagos University Teaching Hospital, Idi-Araba, Lagos).

How Can Lassa Fever Be Managed?

Treatment of Lassa Fever

There is no vaccine available against Lassa fever. The antiviral drug Ribavirin seems to be an effective treatment for Lassa fever if given early on in the course of clinical illness. There is no evidence to support the role of Ribavirin as post-exposure prophylactic treatment for Lassa fever.

Oral Ribavirin given as prophylaxis or preventive treatment has been studied in a limited fashion during an outbreak, with no evidence of transmission; however, only 40% of the small number of participants completed treatment due to side effects from Ribavirin that included weakness, dizziness, headache, and nausea.

In light of the severe 2018 outbreak in Nigeria, the World Health Organization and several global public health entities are working tirelessly to develop an effective vaccine.

Managing Lassa Fever Cases

In managing Lassa fever, there are suspected, probable, and confirmed cases, with each category being managed differently.

In suspected cases:

• Put the patient in a holding area and institute infection-prevention measures
• Alert the relevant authorities: infectious disease team or responsible physician
• Notify relevant public health authorities e.g., State Epidemiologist, LGA Disease Surveillance and Notification Officer)
• Start rehydration. Commence Fluid therapy
• Monitor vital signs every 4 hours (Pulse Rate, Blood Pressure, Respiratory Rate, Temperature) and Monitor Urinary output
• Carry out dipstick urinalysis for protein and blood
• Test for the presence of malaria parasites preferably through Rapid Diagnostic Test (RDT), and check full blood count including platelets count, serum electrolytes, urea and creatinine, and liver function test (LFT)
• Take blood to a laboratory for diagnostic testing (RT-PCR) or Serology using RDT

In probable cases:

• Transfer the patient to the suspect bay of the treatment unit/center and commence supportive care. Then start treatment with Ribavirin.
• Assess the patient for possible complications and manage accordingly
• Review Ribavirin treatment with Polymerase Chain Reaction (PCR) result. If PCR is negative, the continuation of treatment with Ribavirin is at the discretion of the attending doctor

In Confirmed Cases:

• Transfer the patient to the treatment unit/center
• Commence supportive care
• Continue treatment with Ribavirin if the patient has been on it before confirmation
• Start treatment with Ribavirin, if the patient is newly confirmed for Lassa fever
• Assess the patient for possible complications and manage accordingly

This leads to being quarantined in a special section of the hospital. And at hospitals where Lassa fever is practicable, all cases (suspected, probable, and confirmed cases) are further separated into ‘wet’ and ‘dry’ categories. Wet includes bleeding, vomiting, diarrhea, coughing, and sneezing; while ‘dry’ includes patients without wet symptoms

For a suspected case who has established contact with a confirmed case, the commencement of Ribavirin should be immediate while lab results OR if clinical features strongly support the diagnosis of Lassa fever.

Who is a contact? A contact is a person who has been exposed to an infected person or an infected person’s secretions, excretions, or tissues within three weeks of last contact with a confirmed or probable case of Lassa fever.

It is the public health responsibility to:

• Identify, assess, and categorize contacts of patients with Lassa fever
• Ensure the appropriate monitoring of high-risk contacts
• Arrange further evaluation for contacts that develop a temperature of ≥38°C within 21 days of the last possible exposure
• Consider and arrange antiviral prophylaxis, as necessary

Prevention of Lassa Fever

Prevention of Lassa fever relies on promoting good community hygiene to discourage rodents from entering homes. This can be possible by:

• Removing the source of attraction for rats: Storing grain and other foodstuffs in rodent-proof containers, disposing of garbage far from the home, maintaining clean households, and washing dishes after eating.
• Preventing rats from entering the house: blocking holes around the house, improving building materials and structures (ceiling, walls), and keeping cats and dogs.
• Avoid contact with infected rats and consumption of their raw meat. Rats should be handled with gloves and other appropriate protective clothing.
• All animal products should be thoroughly cooked
• Family members should always be careful to avoid contact with blood and body fluids while caring for sick persons.
• Healthcare staff should always apply standard infection prevention and control precautions when caring for patients, regardless of their presumed diagnosis. These include basic hand hygiene, respiratory hygiene, use of personal protective equipment (to block splashes or other contact with infected materials), safe injection practices, and safe burial practices.
• Workers caring for patients with suspected or confirmed Lassa fever should apply extra infection control measures to prevent contact with the patient’s blood and body fluids and contaminated surfaces or materials such as clothing and bedding.
• When in close contact (within 1 metre) with patients with Lassa fever, health workers should wear face protection (a face shield or a medical mask and goggles), a clean, non-sterile long-sleeved gown, and gloves (sterile gloves for some procedures)
• Samples taken from humans and animals for investigation of Lassa virus infection should be handled by trained staff and processed in suitably equipped laboratories under maximum biological containment conditions.