What hantavirus is and how deadly it can be

A deadly outbreak aboard a cruise ship in the southern Atlantic has cast a spotlight on hantavirus, a rodent-borne disease that can prove fatal when it infects humans.

Dutch cruise operator Oceanwide Expeditions said it was handling “a serious medical situation” on board the MV Hondius, which was sailing from Argentina to Cape Verde.

Hantaviruses belong to a group of pathogens capable of triggering respiratory and cardiac complications, along with haemorrhagic fevers.

No vaccine or targeted treatment exists for hantaviruses, so care is limited to easing symptoms and supporting the patient.

There are multiple hantavirus strains, differing by region and by the illnesses they cause, according to Switzerland’s FOPH health ministry.

“Human-to-human transmission has only been observed with one single virus type, which is extremely rare,” it says.

Hantaviruses have been identified on every continent.

The virus takes its name from the Hantan River in South Korea, where more than 3,000 troops became seriously ill after infection during the 1950-1953 Korean War, the FOPH says.

Transmission

People contract hantaviruses through infected wild rodents, including mice and rats, which release the virus in saliva, urine and droppings.

Infection can result from a bite, direct contact with the animals or their waste, or from inhaling contaminated dust.

The French National Public Health Agency says people are generally infected by breathing in dust and aerosols tainted by the excretions of infected animals.

Hantaviruses spread to humans through infected wild rodents

This most often happens “during activities in forests, or in long uninhabited buildings near forests, as well as during activities in rural areas where fields and farms offer a favourable environment for reservoir rodents”, it says.

The best way to reduce the risk of infection is to avoid rodents and any contact with their secretions and excretions.

World Health Organization Europe director Hans Kluge said hantavirus infections are “uncommon” and that the disease “is not easily transmitted between people”.

“The risk to the wider public remains low. There is no need for panic or travel restrictions,” he said.

Diagnosis

The WHO says suspected infections can be confirmed through a range of laboratory tests, including detection of “the presence of hantavirus-specific IgM antibodies”.

Onset

The two main illnesses linked to hantavirus are haemorrhagic fever with renal syndrome (HFRS), associated mainly with Europe and Asia, and hantavirus pulmonary syndrome (HPS), linked to viruses found in the Americas.

In the Americas, hantavirus strains can also lead to pulmonary oedema or acute respiratory failure.

Health agencies differ somewhat on how long it takes for symptoms to appear after exposure.

The earliest signs of hantavirus often resemble the flu

According to the US Centers for Disease Control and Prevention (CDC), symptoms of HPS generally emerge between one and eight weeks after contact.

The CDC says HFRS symptoms typically appear within one to two weeks of exposure, though in rare instances they can take as long as eight weeks.

Symptoms

While most hantavirus infections go unnoticed, Switzerland’s FOPH says the disease can range widely in severity in humans and can at times be fatal.

Early symptoms usually mirror the flu, with fever, headache and muscle pain.

The CDC says that four to 10 days after the initial phase of HPS, later symptoms develop, including coughing and shortness of breath. “Patients might experience tightness in the chest, as the lungs fill with fluid,” it says.

Hantavirus strains circulating in Europe and Asia can also impair kidney function and, in severe cases, cause acute kidney failure.

Fatality rate

The Public Health Agency of Canada says about 200 HPS cases are recorded each year, mainly in North and South America, with an average case fatality rate of 40%.

It says there are between 150,000 and 200,000 HFRS cases worldwide each year, most of them in China, where the average case fatality rate ranges from one to 12%.