Lassa Fever: Causes, Symptoms & Vaccine

LASSA FEVER, CAUSES, SYMPTOMS, TREATMENT

 

1. Overview

The Lassa fever is a notifiable disease and belongs as the Marburg fever to the viral haemorrhagic fevers.

2 . Definition of Lassa Fever

Lassa fever is a febrile viral disease that can lead to internal bleeding. Thus, it is a haemorrhagic infectious disease ( haemorrhagic = associated with internal bleeding).

The Lassa virus responsible for Lassa fever is not the only virus that can trigger a hemorrhagic fever . Other virus-related haemorrhagic fevers include:

• yellow fever
• Marburg virus infection
• Dengue fever (or dengue hemorrhagic fever, DHF)
• Ebola

All viral haemorrhagic fevers (including Lassa fever) are notifiable diseases .

Lassa fever and Ebola fever causes in Africa

The term Lassa fever is due to an international agreement stating that a hemorrhagic fever should be named after the site of its discovery. Lassa fever was discovered in 1969 in Lassa, Nigeria, where two American nurses from a mission station died of an unexplained fever disease, and a third sister, who showed signs of haemorrhagic fever, was taken to the United States. She survived the disease; the pathogen was identified as a previously unknown virus.

Frequency of occurrence

Lassa fever is estimated to occur at a rate of approximately 100,000 to 300,000 cases, predominantly in the tropical regions of West Africa. During the dry season from January to April, a seasonal accumulation is observed. In the US and in Europe, isolated cases occur.

CAUSES OF LASSA FEVER

The Lassa fever is caused by viruses. The complaints of Lassa fever are initially very unspecific. After an incubation period of about 3 - 21 days it can come to fever. In most cases (80%), the Lassa fever heals without major discomfort and leads only in a few cases to a life-threatening course of shock and organ failure. The disease "Lassa" is named after a city in northeastern Nigeria. There the disease was described in 1969 and the virus was detected for the first time. The Lassa fever is - especially for travelers - a very rare, but at the same time a very serious illness. Around 10 to 20% of inpatients die as a result of the virus infection. The incidence of Lassa fever has so far been reported from the following countries: Nigeria, Liberia,

Routes of infection

The infection with the Lassa fever is due to a lack of hygienic conditions. As causes, several infection routes are possible:

Transmission from animal to human: Causes of the Lassa fever may be infected rats, the Lassa virus indirectly (via virus-containing suspended matter in the air, which are caused by dried excreta such as urine or feces) or directly (via direct contact with blood and Excretion or consumption of contaminated food).

Transmission from person to person: Lassa fever can also be caused by infection in humans (via blood-containing suspended substances in the breathing air as well as through direct contact with blood, saliva, urine, semen, vomit or feces of acutely affected persons).

incubation period

In Lassa fever, the incubation period (ie the time from infection to the onset of the disease) can be 6 to 21 days. Mostly, however, it takes 7 to 12 days.

4 . Symptoms of Lassa Fever

The Lassa fever causes mostly (in 80% of cases) little or only mild symptoms. Internal bleeding, which is why Lassa fever is also called haemorrhagic fever ( haemorrhagic = with internal bleeding), occurs only in a part of the cases.

Typically, Lassa fever begins slowly as the fever increases , with symptoms similar to the onset of flu . In about half of those affected it comes to muscle pain and joint pain , usually in the lumbar spine. On the third to fourth day, a dry cough with severe sore throat occurs; on the almonds can form white or yellow coverings. Strong headaches develop; In addition, those affected feel chest pain.

In about two-thirds of cases, Lassa fever causes abdominal cramps associated with vomiting. In severe cases of viral disease, other symptoms may include conjunctivitis associated with internal bleeding (hemorrhagic conjunctivitis), and swelling of the face and neck, which may adversely affect the prognosis.

In about one in five affected Lassa fever leads to pericarditis (pericarditis). The blood pressure is usually low and the circulation can fail. Renal failure is also common. In complicated cases, encephalitis is possible. About one in four sufferers experience severe bleeding. These symptoms can be life threatening.

5 . Diagnosis

In Lassa fever, the diagnosis succeeds by detecting the pathogens or specific antibodies. Even at the first suspicion of infection with the Lassavirus, it is advisable to take blood samples to ensure a quick diagnosis

The viruses responsible for the Lassa fever are detectable in the blood, in the pharynx, in the urine or in tissue samples. The Lassa virus is grown in tissue cultures or in mouse or guinea pig babies. For several years, the polymerase chain reaction (PCR) has also been available for diagnosis in order to detect the virus. From the third day of the disease on Lassa fever specific immunoglobulin M and immunoglobulin G antibodies can be detected in the blood of those affected.

6 . Treatment of Lassa fever

In Lassa fever, therapy is primarily aimed at alleviating the symptoms. It is also important to provide sufficient fluids to those affected.

If Lassa virus is suspected, treatment with ribavirin is advisable in addition to symptomatic treatment. In order to inhibit the proliferation of viruses, those affected are best given the drug via the vein (intravenously). It is important that this treatment begins on the first six days of illness: Early treatment can lower the mortality rate (lethality) that is quite high in Lassa fever. By over the mouth (orally) administered drugs, the mortality decreases by a factor of three; when given intravenously, the mortality even falls by a factor of ten.

7 . Course of Development

The Lassa fever predominantly (80%) takes a smooth course. Internal bleeding, which is why Lassa fever is also called haemorrhagic fever ( haemorrhagic = with internal bleeding), develops only in a part of the cases.

Typically, Lassa fever sets in slowly, with the entire course lasting on average for 12 to 15 days (4 weeks maximum). In severe disease progression, the prognosis is difficult to assess. Whether those affected recover or die, usually decides between the second and third week of illness.

Complications of Lassa Fever

The Lassa fever may be associated with various complications in severe cases: For example, a brain inflammation (encephalitis) is possible, which can lead to damage to the eighth cranial nerve, which in turn produces a permanent numbness .

Mortality

If the Lassa fever is severe, the then very high mortality (lethality) can be significantly reduced by early intravenous treatment with ribavirin. On average, hospital mortality is 15 percent. During pregnancy it is even higher: About half of all pregnant women die from Lassa fever; More than 80 percent of those affected lose their child.

8 . Prevention of Lassa Fever

The most effective way to prevent Lassa fever is to avoid contact with rats and people who are ill and to pay close attention to hygiene in the area around the virus. In order to prevent the spread of Lassa fever in the hospital, a strict isolation of those affected and a protective equipment for the medical personnel (gowns, gloves, mask and goggles) are necessary.

Diseased people are contagious, especially in the acute feverish phase. However, they excrete the Lassa virus responsible for the Lassa fever much longer: in the urine for 3 to 9 weeks after onset of the disease, in the seminal fluid even up to 3 months. Therefore, with Lassa fever sexual abstinence is also advisable for the prevention of contagion. There is no vaccine against Lassa fever. However, a once-through disease seems to protect against a renewed Lassa fever: Who survives the infection, although again infected with the Lassa virus, but not again fall ill.

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Legal

Those affected by Lassa fever must be reported by name. Notifiable are the suspicion of Lassa fever and the present disease of Lassa fever, as well as the direct detection of the pathogen.