Carried by wild rodents, Hantaviruses are responsible for viral infections (zoonosis) in humans. In France, they are responsible for around XNUMX cases of renal hemorrhagic fever (FHSR) per year, which occur near forests. Generally not serious, they can nevertheless cause hemorrhagic and renal complications. Hantavirus cardiopulmonary syndromes (HPS) observed in the Americas are more serious and often fatal.

Definition

Hantaviroses are viral infections (viral infections) caused by viruses of the genus Hantavirus.

Hantaviruses (family Bunyaviridae), whose natural hosts are certain species of rodents or wild insectivores (shrews, moles, etc.), are found on all continents. Those which are transmissible to humans and are the cause of renal hemorrhagic fevers (RFS) in Europe and Asia or of Hantavirus pulmonary syndrome (HPS) in the American continent, especially in Latin America.

There are around a hundred varieties of hantavirus, four species present in Europe being capable of causing zoonoses (infections transmissible from animals and humans). In France, hantavirosis is mainly due to the Puumala virus, which circulates in northern and western Europe. Its natural host is the russet vole.

Causes

Human contaminations are generally due to the inhalation of dust contaminated by the urine, saliva or excrement of healthy animal carriers which constitute their reservoir. They generally occur during activities in the forest or in uninhabited premises on the edge of forests.

Transmission through direct contact between contaminated material and injured skin or through ingestion of contaminated food or water is much rarer.

No human-to-human transmission has been reported on the Eurasian continent, the only cases described concerning the South American Andes hantavirus.

Diagnostic

Faced with clinical signs suggestive of the disease, the doctor will seek to know if his patient has handled wood or cleaned a room that has remained uninhabited for a long time in the previous two months.

Biological parameters such as a decrease in the level of blood platelets (thrombocytopenia) or the presence in the urine of proteins (proteinuria) and traces of blood (microscopic hematuria) make it possible to guide the diagnosis.

Ultrasound can also be helpful in revealing typical features of this infection, including increased kidneys and spleen.

Blood tests (ELISA or IF tests) are performed by medical or hospital biology laboratories to detect virus-specific IgM and IgG antibodies present in the patient’s blood and to confirm the diagnosis.

The tests which make it possible to detect viral RNA are not marketed.

The people concerned

Hantavirosis is relatively rare in countries such as France or the United States, but much more frequent in others: there are thus several hundred to thousands of cases per year in Germany and Scandinavia.

In mainland France, around a hundred cases on average (only 14 in 2013, but 232 in 2017) are detected each year in the north-eastern quarter of the country, with epidemic outbreaks north of the Ardennes, in Avesnois, in the north and in the center of the Aisne, south of the Oise, in the Doubs or in the Jura. Peaks in detection are observed in late spring and fall. Cases of cardiopulmonary Hantavirus (HPS) syndromes are sporadic in the Antilles-Guyana region.

In France, men are two to three times more affected than women by hemorrhagic fever with renal syndrome. Foresters, farm workers and construction workers are mainly affected.

Risk factors

The main risk factor in mainland France is exposure to a contaminated dusty environment, during certain activities such as cutting, skidding or handling wood, cleaning henhouses, barns and sheds, working in old houses. or any other activity that suspends dust.

Although it is most often benign, the haemorrhagic haemorrhagic renal syndrome can cause more or less severe symptoms.

Flu syndrome

The first symptoms, which appear a week to two months after infection, mimic those of the flu. The fever can reach 39 to 40 ° for two to four days, and stabilizes around 38 ° the following days. It is sometimes accompanied by chills and headaches.

pain

The pain, which is resistant to the usual analgesics, sets in a little later. It can be muscle pain, abdominal or chest pain, low back pain, joint pain, or even dental pain.

Vision disturbances

Fleeting vision disorders, of the “acute myopia” type, appear in 40% of cases and are very suggestive of the disease.

Other signs

• Discreet hemorrhagic signs (bleeding gums, etc.)
• Discreet respiratory manifestations in a third of cases

Evolution

Kidney failure sets in secondarily in more than half of the cases. Liver damage can also be observed. Fortunately, severe complications – hemorrhagic symptoms, whether or not associated with acute renal failure, neurological disorders, etc. – remain rare and healing is generally achieved without sequelae after a few weeks of severe fatigue. However, the disease is fatal in one to two cases in a thousand.

Specificity of American SPHs

American hantaviruses have pulmonary and non-renal tropism. In cardiopulmonary syndrome, fever is followed by difficulty breathing which can get worse very quickly. Four of the five cases detected in Guyana were fatal.

There is no specific treatment for haemorrhagic fevers with renal syndrome caused by Hantaviruses. Management is therefore only symptomatic.

Drugs like aspirin, anti-inflammatory drugs, and some antibiotics should be avoided due to their toxicity to the kidneys.

Dialysis sessions may be necessary in cases of acute renal failure.

Prevention relies on an arsenal of precautions to be taken to avoid exposure to the virus in areas frequented by the red vole where it is endemic.

The authorities advise to avoid coming into contact with rodents or their corpses and to fight against their presence, by preventing their access to homes and, if necessary, by pest control of homes located in the forest or on the edge of the forest.

Work in dusty premises likely to have housed them should not be carried out without protection (mask, etc.).

Finally, people exposed to contact with rodents through their work must comply with certain hygiene measures, in particular covering wounds with bandages.