Lassa Fever: History, Signs & Symptoms, Cause, Prevention And Treatment (Be Informed)

The resent outbreak of Lassa fever in Nigeria is a thing of concern to all. Minister for health, Prof. Isaac Adewole has confirmed the death of 40 people to this outbreak!! 

It has been reported in more than six states now! 

I bring this to you so that the damaging effects can be reduced, if people are conscientized on their ways of life as to what to do and not to do. 

This will go in no small way to checkmate it. Read and be updated. 

History of Lassa fever 

Lassa fever or Lassa hemorrhagic fever(LHF) is an acuteviralhemorrhagic fevercaused by the Lassa virus and first described in 1969 in the town of Lassa, in Borno State, Nigeria.

Lassa fever is a member of the Arenaviridae virus family. Similar to Ebola, clinical cases of the disease had been known for over adecade, but had not been connected with a viral pathogen.

Lassa frequently infects peopleinWest Africa. It results in 300,000 to 500,000 cases annually and causes about 5,000 deaths each year.

Outbreaks of the disease have been observed inNigeria,Liberia,Sierra Leone,Guinea, and theCentral African Republic. 

The primary animal host of the Lassa virus is theNatal multimammate mouse(Mastomys natalensis), an animal found in most ofsub-Saharan Africa.

The virus is probably transmitted by contact with the feces or urine of animals accessinggrainstores in residences.

Given its high rate of incidence, Lassa fever is a major problem in affected countries.

Signs and symptoms

In 80% of cases, the disease isasymptomatic, but in the remaining 20%, it takes a complicated course. 

The virus is estimated to be responsible for about 5,000 deaths annually. The fever accounts for up to one-third of deaths in hospitals within the affected regions and 10 to 16% of total cases.

After anincubation periodof six to 21 days, an acute illness with multiorgan involvement develops.

Non specific symptomsincludefever, facial swelling, and muscle fatigue, as well as conjunctivitis and mucosal bleeding. 

Cause

Mastomys natalensis, the natural reservoir of the Lassa fever virus Lassa virus is zoonotic (transmitted from animals), in that it spreads to humans fromrodents, specifically multimammate mice (Mastomys natalensis).

This is probably the most common mouse in equatorial Africa, ubiquitous in human households and eaten as a delicacy in some areas.

In theserodents, infection is in a persistentasymptomaticstate. The virus is shedin their excreta (urine and feces), which can be aerosolized. 

In fatal cases, Lassa fever is characterized by impaired or delayed cellular immunity leading tofulminantviremia.Infection inhumanstypically occurs by exposure to animal excrement through the respiratory orgastrointestinal tracts. 

Inhalation of tiny particles of infectious material (aerosol) is believed to be the most significant means of exposure. 

It is possible to acquire the infection through brokenskinormucous membranesthat are directly exposed to infectious material.

Transmission from person to person has also been established, presenting a disease risk for healthcare workers. Frequency of transmission by sexual contact has not been established.

Prevention 

Control of theMastomysrodent population is impractical, so measures are limited to keeping rodentsout of homes and food supplies, as well as maintaining effective personal hygiene. 

Gloves, masks, laboratory coats, and goggles are advised while in contact with aninfected person. 

These issues in many countries are monitored by a department ofpublic health. In less developed countries, these types of organizations may not have the necessary means to effectively control outbreaks.

Researchers at theUSAMRIIDfacility, where military biologists study infectious diseases, have a promising vaccine candidate.

They have developed areplication-competent vaccine against Lassa virus based on recombinant vesicular stomatitis virus vectors expressing the Lassa virus glycoprotein. 

After a singleintramuscular injection, test primates have survived lethal challenge, while showing no clinical symptoms.

Treatment

All persons suspected of Lassa fever infection should be admitted to isolation facilities and their body fluids and excreta properly disposed of.

Early and aggressive treatment using ribavirin was pioneered by Joe McCormickin 1979. After extensive testing, early administration was determined to be critical to success. 

Additionally, ribavirin is almost twice as effective when given intravenously as when taken by mouth.

Ribavirin is aprodrugwhich appears to interfere with viral replication by inhibiting RNA-dependentnucleic acid synthesis, although the precisemechanism of actionis disputed.

The drug is relatively inexpensive, but the cost of the drug isstill very high for many of those in West African states. 

Fluid replacement, blood transfusion, and fighting hypotension are usually required. Intravenousinterferontherapy has also been used.

When Lassa fever infects pregnant women late in their third trimester, induction of delivery is necessary for the mother to have a good chance of survival.

This is because the virus has an affinity for the placenta and other highly vascular tissues. The fetus has only a one in ten chance of survival no matter what course of action is taken; hence, the focus is always onsaving the life of the mother.

Following delivery, women should receive the same treatment as other Lassa fever patients.

Work on a vaccine is continuing, with multiple approaches showing positive results in animal trials.

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