Lassa fever

Lassa fever: description

Lassa fever is an infectious disease and is one of the so-called haemorrhagic (bloody) forms of fever. These include virus-induced Ebola fever, yellow fever, or Bolivian hemorrhagic fever. They are all very similar in their symptoms, making it difficult for doctors to make the right diagnosis quickly.

The pathogen responsible for the Lassa fever was first discovered in 1969 in Lassa, a city in Nigeria. Therefore, the disease carries the name of this city.

Lassa fever: spreading

Lassa fever is endemic in some West African countries. These include Sierra Leone, Guinea, Liberia, Benin and Nigeria. An endemic area is a region in which a pathogen is permanent and can not be removed. In the case of Lassa fever, the virus can not be displaced from the region as it is transmitted to humans by rodents (the African tycoon, Mastomys natalensis). In some areas all live rats carry the Lassa virus and not all of them can be eliminated.

Lassa fever: illness

It is estimated that about 300,000 people a year become infected with Lassa fever. Of these, 80 percent of the cases are mild or completely asymptomatic. About one to two percent of the patients die.

Lassa fever disease rarely occurs outside the endemic area. Often, the infected are travelers who have recently been in West Africa and infected with Lassa fever. Since 1974, five cases of Lassa fever have occurred in Germany. All patients had been infected with the virus abroad. Two of them died.

Lassa fever: symptoms

The Lassa fever can be mild or even asymptomatic, as well as very difficult to a fatal outcome. The disease begins after an incubation period of 6 to 21 days. This is the time between the infection with the pathogens and the onset of symptoms.

Lassa fever begins with common signs of illness that are flu-like. These include:

• fatigue
• Headache and body aches
• fever
• Pain behind the sternum
• to cough
• Nausea and vomiting
• Conjunctivitis

For the Lassa fever as the cause of disease usually speak a painful inflammation of the throat and a rarely occurring rash, which stands out somewhat from the skin level.

If there is a severe course of Lassa fever, the following symptoms often occur from the second week of illness:

• Water retention (edema) in the eyelids and face
• mucosal bleeding
• Fluid accumulation in the lung and pericardium (pleural and pericardial effusions)
• Lose consciousness
• slowed heartbeat (bradycardia)
• low blood pressure (hypotension)

In severe cases, circulatory and renal failure as well as severe bleeding and cerebral involvement in the form of encephalopathy may occur.

Lassa fever: causes and risk factors

The cause of Lassa fever is the so-called Lassa virus. It is one of the arenaviruses. These particles consist of a shell and a genetic material packed in it and need a host in whose cells they can multiply. In addition to humans, they use rodents as hosts, which can carry the virus without getting sick. One speaks of vectors.

Lassa fever: transmission by Vielzitzenratte

Via the urine or feces of the rats, the Lassa viruses enter the environment. Because the multinationals live mostly near human settlements, humans can easily come into contact with the viruses. In some cases, 50 to 100 percent of the rat populations of a village are infected with the Lassa virus. For example, food contaminated with rat excrement, such as grain, causes people to become infected. In some areas, the tuxedo rats are hunted and consumed. Also, there is a danger of infection.

A transfer from person to person is also possible. For example, in the care of sick relatives – for example, when you come into contact with feces or blood of the patient. Likewise, the pathogens can be inhaled or penetrate into the body through injuries of the skin. Even during intercourse, infection is possible, as well as in pregnant women on the placenta to the child.

Lassa fever: risks for a severe course

The cases of the past show that especially pregnant women are at risk of suffering from a severe Lassafieber course. The mortality of pregnant women is significantly above average. In addition, the virus can be transmitted via the donut cake to the unborn child. The infection is almost always deadly to the fetus.

Lassa fever: examinations and diagnosis

The similarity between Lassa fever and other febrile conditions such as flu or malaria makes it difficult for the doctor to make the right diagnosis quickly. Therefore, the questions about the history of the disease (anamnesis) and especially after the last travel destinations (travel anamnesis) are extremely important. Your doctor will ask you, among other things:

• Since when do you feel sick?
• Do you have fever?
• Have you been abroad recently?
• Did you have contact with persons who are also ill?

Then follows the physical examination. Your temperature and your blood pressure are measured, your doctor scans your belly and listens to your heart and lungs.

Lassa fever: A blood test provides information

To diagnose Lassa fever in case of suspicion of the disease, medics get a blood test. For this you will be given blood at the beginning of treatment. This is being tested in high-security laboratories under strict conditions. On the one hand with the help of so-called molecular genetic tests, the genetic material of the viruses is directly detected. On the other hand, specific antibodies are sought in the blood which are directed against the Lassa virus. These only occur in the body when you have come in contact with the Lassa virus.

Lassa fever, or another disease?

The nonspecific symptoms of Lassa fever make it difficult for the doctor to make the right diagnosis. Flu, Ebola, malaria, dengue fever, typhoid fever, and some other infectious diseases must be distinguished from possible Lassa fever.

Lassa fever: treatment

Since Lassa fever can be fatal, timely treatment with the right medication is extremely important. It is crucial that the therapy begins within the first six days after the onset of the disease. As a drug ribavirin is used. It is an agent that works specifically against viruses. It can be administered both via the mouth (tablet) and via a vein (injection). In severe cases of Lassa fever, the remedy can reduce mortality to below ten percent.

In addition, patients with Lassa fever are cared for at an isolation ward around the clock. This is mainly about the symptomatic therapy. This means treating the symptoms that the patient suffers the most. Among other things, this form of treatment includes the monitoring of blood pressure or the lowering of fever. The isolation of patients should prevent the disease from spreading. In Germany, there are eight different clinics that specialize in the treatment of Lassa fever patients.

Lassa fever: disease course and prognosis

Patients who suffer from Lassa fever, with the right therapy from about the second week of illness to improve the symptoms. After the illness, many sufferers feel weak for a long time and it takes some time until their body has fully recovered from the Lassa fever. Some patients suffer from deafness or gait disorders after Lassa fever. These complaints can subside in the further course.

In severe cases, Lassa fever patients often die around the twelfth day of illness. Above all, circulatory and renal failure play a major role. Brain involvement in the disease in the form of encephalopathy and severe bleeding also worsen the prognosis. Pregnancy is also considered a risk factor for a severe course and increased mortality. The majority of patients survive infection with timely therapy and mild history Lassa fever.

So you can protect yourself from Lassa fever

There is currently no vaccine against Lassa fever. Nevertheless, certain behaviors can minimize the risk of infection. If you’re traveling to a Lassa Endemic area, such as Sierra Leone, look for the following:

• Keep food so that it is not accessible to rodents.
• If there is any chance of your food being contaminated with rat droppings or urine, discard them.
• Avoid close physical contact with sick persons. All body fluids can be contagious!
• Tell your doctor that you have recently been abroad if you feel ill after your journey. So he can make the right diagnosis faster.

To prevent an outbreak of Lassa fever in Germany, doctors must report known cases. Already the suspicion of one Lassa feverDisease in Germany is notifiable.