Fever of Wearied

The fever of Wearied is a striking down hemorrhagic Fièvre (caused by a Arenavirus) near to the fever Ebola.

The disease is sometimes called, in French, “fever of Lhassa”, until in famous publications “serious”, while at the same time the disease in a named city of the Nigeria Lassa appeared, without any connection with the town of Lhassa to the Tibet.

This disease is a true plague in Africa of the west where it is responsible for epidemic S mortals when it touches fragile people (taken refuge, children, elderly). Moreover the fever of Wearied is the hemorrhagic fever most often exported out of the borders where it prevails.

The infection is propagated by a Rat then is transmitted between human beings by direct contact with blood, urines, deposit or others liquid biological of a person reached.

Epidemiology

Etiology

The disease is caused by the Virus of Wearied, a Arenavirus of the family of the Arenaviridae. Its Génome is in the form of ARN simple bit.

History

The first cases were reported in the Fifties but it is only into 1969 that the virus could be isolated in a nurse in the city from Lassa to the Nigeria.

The conflicts which affect some of the countries of the zone of endémie cause displacements of population which support the epidemic S. Ainsi the Sierra Leone knew an epidemic of an exceptional width between 1996 and 1997 due to a civil war.

Zone of endémie

The fever of Wearied prevails primarily in West Africa. It is endemic with the Nigeria, in Guinea (Conakry), with the Liberia and in Sierra Leone. According to WHO, it would also touch other countries of West Africa.

Prevalence

In the zones of endémie, up to 50% of the population would be infected by the disease. The epidemiological studies counted between 300.000 and 500.000 cases per annum in the countries of West Africa.

Mortality

5 to 6000 people succumb each year of the fever of Wearied on the 300 to 500.000 cases. The rate of lethality is thus from approximately 1%, but it reaches 15% among in-patients.

In the expectant mother, mortality reaches 30% and the Fœtus dies in 85% of the cases.

Animal tank

The animal which propagates the disease is a Rat kind Mastomys (Mastomys natalensis). The contamination is carried out by contact with its excrements or bite.

A great number of these rodents live in the vicinity, even inside, of the dwellings in the zones of endémie. One of the means of preventing the propagation of the disease thus passes by the fight against this rodent.

Symptomatology

The infection is asymptomatic in approximately 80% of the cases.

The disease incubates during 6 to 21 days. The first clinical signs generally appear 6 days after the infection.

The primary symptoms which appear are not very specific: strong Fevers, aches, Pharyngitis S, Vomiting, Cephalgia S.

In the severe cases, the clinical signs worsen: with the appearance of edema S, Hemorrhage S in the cavity oral, nasal, in the Vagina and the Digestive system, of épanchements pericardial and pleural, and sometimes of Encéphalite S.

At a late stage, the subjects present a state of shock, convulsions, tremors, and generally die two weeks after the appearance of the primary symptoms.

The patients who survive present serious after-effects in a third of the cases: in particular Myocarditis S and a Deafness plain or bilateral. This deafness grows blurred in the 3 months in 50% of the cases.

Diagnosis

The first clinical signs which appear (Fièvre, Vomissements, abdominal pains, Céphalées) are not very specific. They can correspond to many other diseases prevailing in the area like the Paludisme, the Dysenterie, the typhoid fevers, the Yellow fever or others viral hemorrhagic fevers. This is why it is very difficult to diagnose the disease at an early stage.

To confirm with precision the diagnosis, it is necessary to carry out a Sérologie, which is seldom possible in the endemic zones.

Prevention

Disease prevention

There does not exist currently any Vaccin for this disease.

The prevention of the disease passes by the promotion of good a Hygiène to prevent that the rodents do not penetrate in the dwellings. The measures recommended by WHO are: conservation of food in containers resisting the rodents, the elimination of the refuse far from the dwellings, the maintenance of cleanliness inside those and the presence of cats.

Action to be taken in front of a case

Hospitalization
strict Insulation of the patients
Information of the competent authorities
Treatment etiologic and symptomatic vigorous
Identification of the subjects contacts
For the medical personnel: wearing of protective clothing, masks, gloves, aprons, protections of the systematic face
Stérilisation of the material contaminated

Treatment

The only effective cure currently is the injection into intravenous of Ribavirine, a Antiviral used in particular for the treatment of the Hépatite C.

To be effective, the treatment must be managed at the early stage of the disease. Prescribed as of the first 6 days, it makes it possible cause a drop in the rate of lethality of 90%.

This treatment can generate many undesirable effects in particular of the severe Anémie S. These undesirable effects are fortunately reversible after the stop of the treatment.

The low specificity of the early symptoms makes the diagnosis difficult in the first days of the disease. That constitutes the principal limit of this treatment since the Antiviral is effective only at the early stage of the disease. The disease thus remains currently difficult to look after.

Project in progress

Currently of many laboratories seek a Vaccin against the fever of Wearied . In France in particular of research are carried out by researchers of the Institut Pasteur and INSERM within the Laboratoire P4 to the research center Mérieux-Pasteur in Lyon.

The researchers isolated from the Protéines of surface of the virus which makes it possible to activate the production of Anticorps. However one observes important variations, ata rate of 20%, the level of these proteins. Consequently the immune reactions can be extremely different. To produce an effective vaccine, it would be necessary to succeed in finding the “common denominator” to all these Glycoprotéines which makes it possible to stimulate the production of antibody acting in all the cases.

Thus the hopes are alas quite thin, but these proteins remain the only solutions currently known opening a way towards the development of possible a Vaccin.

External bonds

Page of WHO in connection with the disease

Page of the Pasteur institute on the disease and research carried out

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