LASSA Fever Fact Sheet

         FACTSHEETS ON LASSA FEVER

 

LASSA Fever Fact Sheet

Epidemiology

Lassa Fever is an Acute Febrile disease caused by the Lassa virus belonging to the arenavirus group. It was first described in the 50s and the virus was isolated in 1969 in Lassa, Nigeria. Lassa Fever occurs more often in the dry season, rather than in the rainy season. The multimammate rat (Mastomys natalensis) is the reservoir host of Lassa fever. Deafness is a common sequela, up to 1/3 cases. Case fatality rate varies from as low as 1%-25% to as high as 50%. 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.
Cases have been reported in some states in Nigeria in January 2016 which includes Bauchi, Kano, Nassarawa, Niger, Rivers and Taraba. 
Transmission
Humans usually become infected with Lassa virus from exposure to excreta of infected Mastomys via direct exposure (to the excreta) of rat. Lassa virus may also be spread between humans through direct contact with the blood, urine, faeces, or other bodily secretions of a person with Lassa Fever. There is no epidemiological evidence supporting airborne spread between humans. Person-to-person transmission occurs in both community and health care settings, where the virus may be spread by contaminated medical equipment, such as re-used needles. Sexual transmission of Lassa virus has been reported.
Incubation Period is usually about 10 days but can range from 6-21 days.
Case Definition:

1. Suspected case- Illnesses with onset of Fever, with or without sore throat and at least one of the following signs: bloody diarrhea, bleeding from gums, bleeding into skin (purpura), bleeding into eyes and urine.
2. Confirmed case- A suspected case with laboratory confirmation (positive IgM antibody or viral isolation) or epidemiological link to confirm cases or outbreaks.

Clinical Presentation

1. Mild onset over days:
   - Fever, malaise, headache, myalgia, arthralgia, prostration
2. Gastrointestinal symptoms common
   - Anorexia, nausea, vomiting, diarrhea, abdominal pain
3. Cough, dyspnea, chest pain may be seen
   - Pulmonary edema after IV fluids
4. Central nervous system may be involved in late stages
   - Agitation, confusion, tremor to coma and convulsions
5. Hemorrhage
   - Gastrointestinal, conjunctival injection/sub-conjunctival hemorrhage
6. "Classic" presentation: fever, neck/facial swelling, bleeding (petechial hemorrhage) and shock (but not typical)

• Patients die from combination of increased capillary permeability, cardiac suppression and coagulopathy leading to a low effective circulating volume leading to shock, NOT loss of blood
• Common laboratory findings:
  • Early leukopenia, late leukocytosis
  • Mild-to-moderate thrombocytopenia
  • Elevated hepatic transaminases (AST>ALT)

Laboratory Confirmation
Lassa virus infections can only be diagnosed definitively in the laboratory using the following tests:

• Antibody enzyme-linked immunosorbent assay (ELISA)
• Antigen detection tests
• Reverse transcriptase polymerase chain reaction (RT-PCR) assay
• Virus isolation by cell culture.

This test can be done at Virology Reference Laboratory at Lagos University Teaching Hospital, Idi-Araba, Lagos.

Management
The only known specific treatment for Lassa Fever is Ribavirin and may be effective if given within the first six days of illness. It should be given intravenously for ten (10) days.

• Intravenous Ribavirin treatment should start as soon as a diagnosis of Lassa Fever is made.
• Give a single “loading dose” of 33mg per Kg body weight.
• Then give a dose of 16mg/ Kg body weight every 6 hours for 4 days.
• Then give 8mg/Kg every 8 hours for 6 days.
• Complete treatment course for individual patient clearly laying out the correct amount to give each dose.
• Once started, a Ribavirin treatment should not be discontinued until the 10 days course is complete.
• Supportive treatment should include; Paracetamol, Vitamin K (Phytamenadione), Heamacel, Ringers lactate, Quinine lactate, Quinine injection, and antibiotics- start by I.V.
• If patient is severely anaemic, consider transfusion.

Prophylaxis
Tablets:
Adults 500mg every 6 hours X 5 days
Children > 5 years: 500mg every 12 hours X 5 days
Adverse Effects of Ribavirin
Major side-effect is a reversible, most-often mild anemia. Women who are pregnant or planning to become pregnant are advised not to take Ribavirin
Prevention of Lassa Fever
High Index of suspicion for Lassa Fever should be entertained by health workers to improve case detection. UNIVERSAL PRECAUTION must be practiced in the management of suspected or confirmed cases as listed below:

1. Appropriate personal protective clothings (hand gloves, facemasks, eye goggles and overall) must be worn when attending to cases.
2. Hands must be washed after each contact with patient or contaminated materials. They must first be rinsed in disinfectant and then washed with soap and water.
3. Instruments and Dressings – Each patient must have an individual thermometer labelled with the patient’s name and kept in a receptacle containing disinfectant. The stethoscope and the sleeve of the syphgmomanometre must be decontaminated between each use by rinsing them in disinfectant solution
4. Bed covering – The use of a plastic sheet is essential to avoid the contamination of mattresses. They must be large enough to cover the entire mattress, be waterproof, and be thoroughly disinfected after the discharge or the death of patients.

In case of any suspected case of Lassa Fever, Lagos State Ministry of Health should be notified by calling these GSM numbers: 08022234273, 08037170614 and 08023169485.
Any suspected case should be taken to Mainland Hospital, Yaba.

NOTE: ALL ITEMS WITH POSSIBLE CONTACT WITH ANY CASE MUST BE THOROUGHLY DISINFECTED BEFORE REPEATED USE.