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Hantaviruses are pathogens from the group of RNA viruses that are mainly transmitted by rodents. In the event of contact with pathogens, a person may develop hemorrhagic fever or hantavirus pulmonary syndrome. Although hantavirus infections are not common in Poland, they do occur every year. How are hantavirus diseases diagnosed and treated?
What is a hantavirus?
Hantawirus to RNA virus primarily transmitted by rodents from the family bunyaviridae. It occurs all over the world, but mainly in Asia and Europe; cases of hantavirus infections are also observed in Poland. It has been found that at least a dozen varieties of hantaviruses can be a source of human infection. Hantavirus infection may result in haemorrhagic fever with renal syndrome or hantavirus pulmonary syndrome.
Occurrence of the first case hantavirus infections in Poland was found in 2004, and in 2007 an outbreak appeared in the Podkarpackie Province. Since then, there have been usually several to several dozen cases of infections per year.
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What are the routes of infection with hantaviruses?
Hantaviruses are pathogens transmitted by animals, mainly rodents (e.g. voles, rats, house, field or forest mice), insectivores (e.g. moles, shrews), and bats. These animals are a reservoir of viruses – they do not get sick, but in their bodies, hantaviruses multiply and through them spread to humans.
Hantavirus infection may occur by droplets or through contact with infectious material. This means that a person can become infected:
- by inhaling dust or dirt contaminated with saliva or rodent faeces;
- by contact of rodent excreta with damaged skin or mucous membranes, including consumption of contaminated food or water; infection can also occur after being bitten by an animal carrying the virus.
A person infected with the hantavirus does not infect more people.
Hantavirus infections most often occur in people who live in places inhabited by infected rodents. Therefore, a higher risk concerns people with poorer living conditions, but also those using campsites or performing field work. Rodent research professionals or soldiers operating in harsh environments are also at risk from hantaviruses.
What diseases do hantaviruses cause?
Diseases that develop as a result of hantavirus infection are mainly hemorrhagic fever of various course. The severity of the disease depends on the type of virus the patient has acquired. Particular types of the virus originally appeared in specific areas, hence names such as Seoul virus or Dobrava-Belgrade virus, but over time the pathogens spread to other regions. In Poland, there are cases of infections with Puumala and Dobrava hantaviruses.
Hantaviruses mainly cause two syndromes – hemorrhagic fever with renal syndrome and hantavirus pulmonary syndrome.
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Hemorrhagic fever with renal syndrome
Getting sick with haemorrhagic fever with renal syndrome (HFRS) they appear when infected with the following types of hantaviruses: Puumala virus (PUUV), Hantaan virus (HTNV), virus, Dobrava virus (DOBV) and Seoul virus (SEOV). The disease may be mild epidemic nephropathy (NE)which is common in Europe – it is caused by the PUUV virus. The more severe form, or HFRS, has a more severe course and a higher mortality.
In the case of epidemic nephropathy, the incubation period is on average 3 to 6 weeks. Initial symptoms of NE include fever, headache, lumbar pain, and abdominal pain. The patient develops acute swollen interstitial nephritis, with time vision problems develop, and some develop glaucoma. In the course of NE, only some patients develop mild nosebleeds or skin ecchymosis. However, the risk of complications should also be taken into account, as several percent of patients develop pulmonary edema, Guillan-Barre syndrome and anuria requiring dialysis.
HFRS is a disease more serious than epidemic nephropathy, especially after infection with HTNV or DOBV, because the mortality rate in their case is approx. 5–15%. The probability of death in hemorrhagic fever caused by Seoul or Puumala hantavirus is approx. 1%.
Hemorrhagic fever with renal syndrome is a severe disease, initially with a high fever exceeding 40 degrees Celsius, chills, pharyngitis, headache and muscle pain, as well as a characteristic erythema on the face. The first stage of the disease is followed by other stages – the second stage is hypotension and shock, which leads to up to 1/3 of deaths from HFRS.
In the third stage of the disease, oliguria and kidney failure problems appear; during this period, hemorrhagic diathesis (hemorrhages of various locations) manifests itself and the highest number of deaths occurs. The penultimate phase of the disease is polyuria, and the last, fifth phase of HFRS is recovery, which may take several months.
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Another disease caused by hantaviruses is hantaviral pulmonary syndrome (HPS). The pathogens responsible for this disease are hantaviruses such as Sin Nombre, Andes, Oran, Lechiguanas and Hu39694. HPS pathogens have been confirmed in the Americas.
People with Hantavirus Pulmonary Syndrome initially show HFRS-like symptomshowever, after 3-5 days additional pulmonary symptoms appear (dyspnoea, shallow breathing, cough). The life-threatening risk of pulmonary syndrome is significant as the disease progresses rapidly. Alveolar pulmonary edema appears rapidly, leading to acute cardiopulmonary failure. Mortality in the case of HPS reaches up to 50 percent.
Diagnostics of hantavirus infections
In the process of diagnosing diseases caused by hantaviruses, the important thing is the clinical picture, i.e. the course of the disease, the type of symptoms or their severity. Difficulties in diagnosis may result in flu-like symptoms in the early stages of the disease development. In the case of HFRS, individual phases of the disease may overlap and proceed with unclear severity. On the other hand, early diagnosis of HPS is difficult due to the rapid course of the disease.
The diagnosis of haemorrhagic fever with renal syndrome is possible thanks to the serological ELISA test, which allows to determine the presence of specific antibodies. If there are doubts about the diagnosis, apply testy PCR. Other indicators that may suggest a disease include leukocytosis in laboratory tests, elevated blood creatinine and nitrogen levels, thrombocytopenia, hematuria, and proteinuria. Histopathological examinations are also helpful, showing, for example, bleeding into the renal parenchyma, inflammatory infiltrates in the renal glues, as well as necrotic changes in the kidneys and other organs.
ELISA and Western blots help to diagnose Hantavirus Pulmonary Syndrome. Patients have changes in the lungs on radiographs; there is also thrombocytopenia, leukocytosis, hematocrit increases and albumin decreases.
How is hantavirus infection treated?
There is a lack of specific drugs that would treat diseases caused by hantaviruses. In the case of HFRS, symptomatic treatment is most often applied, the water and electrolyte balance is monitored and, if necessary, corrected. It is also important to control diuresis and to respond to complications of the disease. Antiviral therapy is also used ribavirinintended to inhibit viral RNA synthesis.
A vaccine against hantaviruses has yet to be developed.
The situation is different in the case of hantavirus pulmonary syndrome, which leads to a rapid deterioration of the patient’s condition after only a few days of initial symptoms. Patients with HPS require prompt hospitalization, initiation of acute respiratory distress syndrome (ARDS) treatment, oxygen therapy or support of lung ventilation, as well as administration of inotropic and antihypertensive drugs. Actions must be taken to prevent shock, as well as monitoring the acid-base and water-electrolyte balance.
How to protect yourself from hantaviruses?
The only way to prevent hantavirus infections is to avoid contact with rodents and other animals that may potentially transmit these pathogens. It is also important to be cautious in places where they may leave infectious material (e.g. faeces) or contaminate with excreta dust or dirt. Another way to reduce the risk of infection is to control the rodent population in the place of residence.
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