LASSA FEVER - May Hospital, Shendam

By Dr A. I. Madaki

Lassa fever is viral illness that occurs in West Africa.
The reservoir of the Lassa virus is a rodent of the genus Mastomys known as “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.
80% of people infected will have no or mild symptoms. One on five people will develop a severe disease.

BURDEN OF DISEASE IN WEST AFRICA

58 million population at risk
5,000 estimated number of deaths in West Africa each year
100,000 to 300,000 estimated number of Lassa fever cases in West Africa each year

CLINICAL FEATURES

- The incubation period ranges from 5-21 days.
- With 80% asymptomatic and mild symptoms presentation, overall case fatality rate (CFR) is 1%.
- CFR can reach 15% or more among patients hospitalized with severe presentation.
- Most common symptoms include:
- Gradual onset of fever, malaise and general weakness;
- After a few days: headache, sore throat, muscle pain, chest pain, nausea, vomiting, diarrhea, cough, and abdominal pain.
- In severe cases, patient may present with bleeding, neck/facial swelling and shock.
- Sequelae: various degree of deafness have been shown to occur in 25% of survivors.
*Hearing return after 1-3 months in only 50% of these patients.

PREGNANCY
Particularly severe in pregnant women and their fetuses (fetal death rate greater than 85%)
Increased maternal mortality in third trimester (greater than 30%)

CHILDHOOD

Significant cause of pediatric hospitalizations in some areas of West Africa
Infants (up to 2 years old) can present a ‘swollen baby syndrome’ and is associated with high case fatality rate

DIAGNOSIS

Symptoms are non-specific; clinical diagnosis may be difficult.
Differential diagnosis includes other viral haemorrhagic fevers, yellow fever, malaria, typhoid fever, shigellosis, and other viral and bacterial diseases.
Patient history is essential and should include: exposure to rodents and/or area/village endemic for Lassa and/or contact with Lassa cases
*Definitive diagnosis requires testing:
- reverse transcriptase polymerase chain reaction (RT-PCR) assay
- IgG and IgM antibodies enzyme-linked immunosorbent assay (ELISA)
- antigen detection tests
- virus isolation by cell culture
*Handling and processing specimen requires suitably equipped laboratories under maximum biological containment conditions and staff collecting samples should be trained.

TREATMENT

Intensive supportive care including: monitor fluid and electrolyte balance and renal function, careful rehydration
Supportive drug therapy including : painkillers, antiemetic for vomiting, anxiolytic for agitation, +/-antibiotics and/or antimalarial drugs
Antiviral drug ribavirin can be given early in course of the disease

PREVENTION

Prevention relies on promoting good community hygiene to discourage rodents from entering homes.

Removing source of attraction for rats: Storing grain and other foodstuffs in rodent-proof containers, disposing of garbage far from the home, and maintaining clean households and washing dish after eating.
Preventing rats from entering house: block 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.

REDUCING HUMAN TO HUMAN TRANSMISSION

Avoid contact with infected Lassa patients and deaths.
Regular hand washing with soap and water.
Encourage early treatment in Lassa Treatment Center.
Hand-washing, using gloves and mask when caring for suspect Lassa patient at home and seek for health advice.

REFERENCES