Lassa fever is a viral infection carried by the multimammate rat (Mastomys natalensis), one of the most common mice in equatorial Africa found across much of sub-Saharan Africa. The illness was first discovered in Lassa, Borno state, Nigeria when two missionary nurses succumbed to the virus in 1969. Its name is derived from the village where it was first documented. The virus is primarily transmitted to humans via contact with excreta from rats. The disease occurs throughout the year, but more cases are recorded during the dry season.
Lassa fever is predominantly reported in Sierra Leone, Liberia, Guinea and Nigeria but, because of the Mastomys rat’s high prevalence in neighboring countries, these areas are also at risk. Once a Mastomys rat is infected, it can excrete the virus in its urine, potentially for the rest of its life. This makes the spread of the disease worryingly easy when added to the fact that this species, like other rats, breeds easily and inhabits human homes.
Lassa fever is spread through:
• Direct contact with urine, faeces, saliva or blood of infected rats.
• Eating food or drinking water contaminated with urine, faeces, saliva or blood of rats.
• Person-to-person through contact with blood, urine, saliva, throat secretion or semen of an infected person.
• Touching of floors, beddings and household materials contaminated with urine, faeces, saliva or blood of rats or an infected person.
• Inhalation of air contaminated with urine, faeces, saliva or blood of rats or an infected person.
Signs and symptoms
Symptoms appear two to 21 days after contact with the Lassa fever virus. The symptoms of the disease usually start with a fever and general body weakness. Other symptoms include: High fever (38.5oC or above), sore throat, vomiting, diarrhea, back pain, cough, chest pain, abdominal pain, restlessness, swelling of the face, bleeding through body openings (nose, ears, eyes, mouth, etc.)
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 deafness, occurring in around one third of cases. The deafness varies in degree and is not necessarily related to the severity of the symptoms. Deafness caused by Lassa fever can be permanent and total.
Because the symptoms of Lassa fever are so varied, diagnosis can be difficult. Clinically, the disease can appear similar to other viral hemorrhagic fevers, including the Ebola virus, malaria and typhoid. The only definitive tests for Lassa fever are laboratory-based where the handling of specimens can be hazardous; only specialized institutions can conduct these tests.
Treatment of Lassa fever
If prescribed early on, the antiviral drug ribavirin has proven useful in fighting Lassa virus; to date, however, its mechanism of action is still subject to debate. During the course of the disease, it is important to manage fluid levels, electrolyte balance, oxygenation and blood pressure in the patient.
Unfortunately, ribavirin is potentially toxic and teratogenic (mutation-causing). It does not have a prophylactic capability and, currently, there is no vaccine for Lassa fever. However, work on a vaccine is underway.
Prevention and Control
The Nigeria Centre for Disease Control (NCDC) advices that standard precautionary measures should be taken by healthcare workers to reduce the spread of Lassa fever in the country. Health care workers are strongly advised to always practice universal standard care precautions when caring for patients, regardless of their presumed diagnosis. Health-care workers seeing a patient suspected to have Lassa fever should immediately arrange for laboratory testing and report to the Local Government disease surveillance and notification officers (DSNOs).
It is important to note the following while caring for Lassa Fever patients:
• Limit the number of health facility staff and visitors in the patient’s room.
• Ensure proper wearing and removal of full personal protective equipment (face masks, hand gloves, gowns, and goggles) before and after entering the patient’s room.
• Wash hands with soap under running water always.
• Limit invasive procedures and use of injectable medications.
• Appropriate disposal and disinfection of items used by Lassa fever patients such as syringes, thermometers, bedding, clothing, cups, plates, spoons, etc.
• Observe safe disposal of injectables and other sharp items.
• The diagnosis of Lassa fever should be suspected in febrile patients returning from areas where Lassa fever is endemic or when common causes of fever such as malaria have been ruled out.
• Samples taken from suspected patients for investigation of Lassa virus infection should be safely handled by trained staff and transported promptly to approved laboratories.
• Observe safe burial practices.
People at risk of being infected with Lassa fever include:
– People of all age groups who come in contact with the urine, feaces, saliva or blood of infected rats or persons.
– People living in dirty environment. Dirt attracts rats.
– Family members who are taking care of persons infected with Lassa fever.
– Health workers, including;
o Doctors, nurses or other health workers providing direct patient care, without universal precautions.
o Hospital staff who clean and disinfect contaminated surfaces, materials and supplies.
o Laboratory staff who handle blood samples from suspected Lassa fever cases.
o Medical or support staff who prepare or handle dead bodies of Lassa fever patients.
Lassa fever can be treated. Early presentation to a healthcare facility increases the chances of survival. Practice good hygiene and be on the lookout always (Better safe than sorry). Report any case of persistent fever to the nearest healthcare facility immediately.
The more you know, the better for you!