Lassa fever is a severe viral disease that occurs in West Africa. It is a disease of the blood, liver and spleen. It is a viral haemorrhagic fever. Lassa fever was discovered in the year 1969 when two missionary nurses died in Nigeria, West Africa. The cause of the illness was found to be Lassa virus, named after the town in Nigeria where the first cases originated. It is recognized in Guinea, Liberia, Sierra Leone, as well as Nigeria.

Causes
The main cause of Lassa virus is a rodent known as the Multimammate Rat of the genus Mastomys but it is not sure that which species of Mastomys are associated with Lassa fever.

• Mastomys rodents breed very frequently, produce large numbers of children, and are frequent in the savannas and forests of West, Central, and East Africa.
• Mastomys generally readily colonize human homes.
  There are a number of ways in which the virus may be transmitted, or spread, to humans.
• The Mastomys rodents drop the virus in urine and compost. The virus can be transmitted through direct contact with these materials.
• Through touching objects or eating contaminated food
• Through cuts or sores, the virus transmitted in the human body
• It may also spread through person-to-person contact when a person comes into contact with virus in the blood, tissue, secretions, or excretions of an individual infected with the Lassa virus.
• Contact with the virus occurs when a person inhales tiny particles in the air contaminated with rodent excretions
• All these factors together contribute to the relatively efficient spread of Lassa virus from infected rodents to humans.

Signs & Symptoms
Signs and symptoms of Lassa fever typically occur 1-3 weeks after the patient comes into contact with the virus. These include

• Abdominal Pain
• Back Pain
• Chest Pain
• Conjunctivitis
• Cough
• Diarrhea
• Facial Swelling
• Fever
• Mucosal Bleeding
• Proteinuria
• Sore Throat
• Vomiting

In severe cases,

• Encephalopathy
• Haemorrhage
• Hypotension
• Pleural Effusion
• Seizures
• Swelling of Face and Neck

Approximately 15% of hospitalized patients die. The disease is more severe in pregnancy, and fetal loss occurs in greater than 80% of cases.

Diagnosis
There are various laboratory tests that are performed to diagnose the disease and assess its course and complications.

• Lassa fever is most often diagnosed by using Enzyme-Linked Immunosorbent Serologic Assays or ELISA, which detect IgM and IgG antibodies as well as Lassa antigen.
• The virus can also be detected by Reverse Transcription-Polymerase Chain Reaction (RT-PCR).

Other laboratory findings in Lassa fever include

• Elevated Aspartate Aminotransferase (AST) levels in the blood
• Lymphopenia (low white blood cell count)
• Thrombocytopenia: low Hb due to bleeding from GI tract
• Coagulation studies and LFTs may also be abnormal.

Preventions

• Isolating infected patients from contact with unprotected persons until the disease has run its course.
• Putting food away in rodent-proof containers and keeping the home clean help to discourage rodents from entering homes.
• Transmission of the Lassa virus from rodent to humans can be prevented by avoiding contact with Mastomys rodents
• Trapping in and around homes can help reduce rodent populations.
• Using infection control measures, such as complete equipment sterilization;
• Wearing protective clothing, such as Masks, gloves, gowns, and goggles
• When caring for patients with Lassa fever, further transmission of the disease through person-to-person contact can be avoided by taking preventive precautions against contact with patient secretions.

Treatments
Death occurs in 15-20% of hospitalized patients. The death rates are particularly high for women in the third trimester of pregnancy, and for fetuses, about 95% of which die in the uterus of infected pregnant mothers. If left untreated, the mortality rate approaches 50%.

• Ribavirin, an antiviral drug, has been given to the success in Lassa fever patients. It has been shown to be most effective when given early in the course of the illness.
• Patients should also receive supportive care consisting of maintenance of appropriate fluid and electrolyte balance, oxygenation and blood pressure, as well as treatment of any other complicating infections.