Lassa fever

Lassa fever awareness campaign in Nigeria-Presentation

Introduction

Lassa fever is an endemic hemorrhagic disease caused by natal multimammate rats common in west African countries like Nigeria.

Historical and Statistical Records of Lassa fever Outbreak

 The history of Lassa fever disease dates back to the 1950s that was the first exposure of
human being to the Lassa virus.
 The first describe case was in 1969 in the town of Lassa in Borno state, Nigeria.
The first documented persons infected with Lassa virus include;
1. Ms. Lily (penny), who was the first documented case of Lassa fever and from whom the
first Lassa virus was isolated in 1969.
 She was infected while working as a nurse at Jos mission hospital in Jos
Nigeria. And she recovered from her infection after being medically
evacuated in the United State.
 She returned from US with a small supply of her own serum intended to
treat her colleague Dr. Jeanette Troup, who as infected with Lassa virus
while performing an autopsy. Unfortunately Ms. Lily arrived ten (10) years
after Dr. Troup's death.
2. Mr. Harry Elyea, who was also a missionary nurse in Nigeria from 1945 to 1968, was
diagnosed positive for Lassa virus in 1972.
 He was told by the clinicians taking care of him that he was not going to
make it .Nevertheless; he eventually recovered to continue his work in
Nigeria. Sadly, Mr. Elyea died nine (9) month after his recovery.
3. The third one is Dr. Hal White, a physician who worked at Jos mission hospital in Nigeria
from 1968 to 1975, during which time he was involved in the investigation of numerous
cases and outbreaks of Lassa fever.
 Dr. White denies having had Lassa fever himself, although he worked in a
hospital where nosocomial transmission of Lassa virus was repeatedly seen.
 Lassa fever is an endemic disease that reoccur every year common in West Africa.
 58 million populations are at risk as reported by the world health organization.
 An estimate of about 100, 000 -300, 000 cases are recorded every year in west Africa,
which result in an average of 5,000 deaths every year
 Therefore, about 1% of all infected patients die yearly, and death frequently occurs
within two week of infection.
 Among those who survive, quarter of them is left with hearing loss.
 Lassa Fever is caused by Lassa Virus

Reservoir of Lassa virus

 Not all species of rats is a carrier of Lassa virus.
 A specie of rats known as mastomys or natal multimammates are the reservoirs, stores, or
carriers of this virus that causes Lassa fever.
 This specie of rats is the most common specie of rats here in West Africa.
 They can quickly reproduce a large number of offspring.
 The rats are usually infected at birth and they are asymptomatic meaning, they show no
any sign or symptom when infected, thereby making it very difficult to differentiate
between infected and uninfected rats.
 Infected rats shed Lassa virus in their urine and feces.

Transmission

Lassa virus could be transmitted by either primary or secondary means:

Primary/Rodent to Human Transmission :( 80 to 90% of cases)

 This account for about 80 to 90 % of all Lassa fever disease cases.
 This happens via;
(1) Direct contact with infected rodents, or their excreta (urine and feces).
(2) Ingestion of food contaminated by an infected rodent.
(3) Inhalation of infected air which is very rare
 Some sources even reported that there is no any reported case of Lassa fever that is
transmitted by the way of inhalation, but it is possible.

Secondary/Human to Human transmission :( 10 to 20 %)

 This account for the remaining 10-20 % of Lassa fever disease cases.
 This can happen via;
(1) Direct contact with blood, secretions, organs or other body fluids of infected
persons.
(2) Ingestion of food contaminated by infected persons.

Clinical Features of Lassa Fever

 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.

Signs and Symptoms.

Signs are the physical complications caused by a disease that is what we can see, while
symptoms are what and how a patient feels.
Onset of symptoms is typically 7 to 21 days after exposure.
 In 80% of those who are infected little or no symptoms occur.
 In 20% of people more severe symptoms occur.
 In those who are pregnant, miscarriage may occur in 95%.
 Lassa fever is especially and particularly severe in pregnant women and their fetuses
where it increases fetal death rate to more than 85% and maternal mortality rate to
more than 30%.
 In cases in which death occurs, this typically occurs within 14days of onset.
 About 1% of all Lassa virus infections result in death.
 Approximately 15% - 20% of those who have required hospitalization for Lassa fever die.
 The risk of death is greater in those who are pregnant.
 A "Swollen baby syndrome" may occur in newborns, infants and toddlers with pitting
edema, abdominal distension and bleeding.

 Most common signs and symptoms include: 

o Gradual onset of fever, malaise and general weakness;

o After a few days: headache, sore throat, muscle pain, chest pain, nausea, 

vomiting, diarrhea, cough, and abdominal pain.

o In severe cases, patient may present with bleeding, neck/facial swelling and 

shock.

o Various degree of deafness has been shown to occur in 25% of survivors. 

o Hearing return after 1-3 months in only 50% of these patients. 

Diagnosis

Diagnosis is the medical procedure used in identifying a disease using signs, symptoms, and 

laboratory findings. Thus, since signs and symptoms of this disease are non-specific, meaning 

they are common to other diseases, diagnosis of Lassa fever may be difficult. The confidence of 

a diagnosis can be compromised if laboratory tests are not available.

One comprising factor is the number of febrile illnesses present in Africa, such as malaria or 

typhoid fever that could potentially exhibit similar symptoms, particularly for non-specific 

manifestations of Lassa fever. For example, In cases with abdominal pain, in countries where 

Lassa is common, Lassa fever is often miss diagnosed as appendicitis and intussusception 

which delays treatment

Symptoms of Lassa fever are common to other viral and bacterial diseases. 

 A range of laboratory investigations are performed, where possible and where available, 

to diagnose the disease and assess its course and complications which include the 

following among others;

(1) RT-PCR (reverse transcriptase chain reaction).

(2) ELISA (enzyme-linked immunobsorbent assay).

(3) Antigen detection test.

(4) Virus isolation by cell culture.

Treatments

There is no specific treatment for Lassa fever disease but rather some commonly used non￾specific treatments are;

1) Intensive supportive care comprising of: 

 monitoring fluid and electrolyte balance 

 renal function and, careful rehydration

2) Supportive drug therapy which is the use of drugs in treating complications caused by 

Lassa fever which may include:

 Painkillers for body pain, antiemetic for vomiting,

 anxiolytic for agitation, 

 and/or antimalarial drugs

• Antiviral drug, ribavirin can be given early in course of the disease

Control and prevention

Control of Lassa fever can be done in the following ways;

 Community engagement and awareness(which is what this presentation is meant for)

 Reducing risk of rats to human transmission

 Reducing human to human transmission.

 Controlling infection in health care settings(nosocomial infection).

Community engagement and awareness

 Engage with communities to promote desired health practices and behaviors, including 

environmental hygiene and food consumption. 

 Provide accurate and timely health advice and information on the disease.

Reducing risk of rats to human transmission

 Keeping of cats to chase rats away from our households.

 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 immediately after eating.

 Preventing rats from entering house: block holes around the house, improving building 

materials and structures (ceiling, walls).

 Avoid contact with rats and consumption of rats 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.

Controlling infection in health care settings

 Implement Standard Precautions with all patients – regardless of their diagnosis – in all 

work practices at all times including safe injection practices. 

 Health care workers treating patient with 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. 

 Laboratory workers are also at greater risk. Samples taken from suspected human Lassa 

fever cases for diagnosis should be handled by trained staff and processed in suitably 

equipped laboratories.

Key Challenges

• Difficulty to control environmental factors

• Difficulty to diagnose patients based on clinical presentation.

• Case investigation to confirm mode of transmission/exposure.

• Candidate drugs are still in early stages of testing

• Vaccines are also still under development 

• Affected countries are at the heart of R&D (Research & Development)