The Japan Times - Hantavirus: spread by rodents, potentially fatal, with no specific cure

Dutch cruise operator Oceanwide Expeditions confirmed Monday it was dealing with "a serious medical situation" on board the MV Hondius, travelling from Argentina to Cape Verde.

Hantaviruses are among the pathogens that can cause respiratory and cardiac distress, as well as haemorrhagic fevers.

There are no vaccines or specific medications to combat hantaviruses, meaning treatment consists solely of attempting to relieve the symptoms.

- The virus -

There are many types of hantavirus, which vary in their geographical spread and their pathologies, 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 are found on every continent.

The virus is named after the Hantan River in South Korea, where more than 3,000 troops fell seriously ill after becoming infected with it during the 1950-1953 Korean War, the FOPH says.

- Transmission -

Hantaviruses are transmitted to humans through infected wild rodents, such as mice or rats, which shed the virus in their saliva, urine, and droppings.

A bite, contact with these rodents or their droppings, or breathing in contaminated dust can cause infection.

The French National Public Health Agency says human infection generally occurs through the inhalation of dust and aerosols contaminated by the excretions of infected animals.

This is typically "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 only way to minimise the risk of infection is to avoid contact with rodents and their secretions and excretions.

The World Health Organization's Europe director Hans Kluge said hantavirus infections are "uncommon" and "it 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 Monday.

- Diagnosis -

Suspected cases can be confirmed through various laboratory tests, according to the WHO, including through "the presence of hantavirus-specific IgM antibodies".

- Onset -

The two most common illnesses caused by infection are haemorrhagic fever with renal syndrome (HFRS), caused by hantaviruses found mostly in Europe and Asia; and hantavirus pulmonary syndrome (HPS), caused by viruses found in the Americas.

The hantavirus types in the Americas can also cause pulmonary oedema or acute respiratory failure.

Different health authorities give varying time periods before symptoms start to manifest.

According to the US Centers for Disease Control and Prevention (CDC), HPS symptoms usually start to show one to eight weeks after contact.

HFRS symptoms usually develop within one to two weeks after exposure, and in rare cases, up to eight weeks, says the CDC.

- Symptoms -

Though most cases of hantavirus infection pass unnoticed, according to Switzerland's FOPH, hantaviruses can cause infections of varying severity in humans -- sometimes fatal.

The first clinical symptoms generally present like flu: fever, headache, and muscle aches.

The CDC says four to 10 days after initial HPS illness, late symptoms appear, which include coughing and shortness of breath. "Patients might experience tightness in the chest, as the lungs fill with fluid," it says.

The types of hantavirus prevalent in Europe and Asia can cause kidney dysfunction and even acute kidney failure.

- Fatality rate -

The Public Health Agency of Canada says around 200 HPS cases occur each year, primarily in North and South America, putting the average case fatality rate at 40 percent.

It adds that between 150,000 and 200,000 HFRS cases occur each year worldwide, most of which are in China, where the average case fatality rate is from one to 12 percent.

S.Ogawa--JT