At least three people have died, and four others have been infected with hantavirus in an outbreak that began last month on a luxury cruise ship carrying 147 passengers and crew. One patient is in critical condition, and three others have mild symptoms, according to the World Health Organisation.

The ship remained anchored off Cape Verde for several days after authorities refused disembarkation over virus concerns, and is now en route to Spain’s Canary Islands.

The UN health body said that the hantavirus cluster is linked to the same vessel, which had passengers and crew from around 23 countries, including Indians.

Media reports suggest the outbreak involves Andes strain, which is common in parts of Argentina and Chile, and some passengers are believed to have recently travelled to the region.

Hantavirus can cause illnesses such as hantavirus pulmonary syndrome (HPS) and haemorrhagic fever with renal syndrome (HFRS).

The US Centres for Disease Control and Prevention has classified the outbreak as a ‘level 3’ emergency response, according to media reports.

The Post has spoken with virologists, epidemiologists, and health officials about the risk of a potential outbreak in Nepal and the measures needed to prevent it.

Here is all you need to know about hantavirus and the risk of an outbreak in Nepal.

What is hantavirus, and how does it spread in humans?

Hantaviruses are a group of rodent-borne viruses that cause serious illness and death in infected patients. Wild rodents—mainly mice and rats—are the primary carriers of hantaviruses. In humans, the virus can cause severe respiratory, renal, and lung failure.

The virus spreads through close contact with the droppings, urine, or saliva of infected rodents, or by touching or cleaning contaminated surfaces, according to the WHO.

Human cases are most commonly reported in rural settings such as forests, fields, and farms. where rodents are present.

Why did the latest outbreak raise global public health concerns?

Hantavirus itself is a serious viral disease with a fatality of around 35 to 40 percent, and in some outbreaks, the fatality rate can reach 50 percent, according to the US Centres for Disease Control and Prevention.

Because at least three people have died and several others are seriously ill and hospitalised, the outbreak has raised global public health concerns.

Passengers on the ship came from multiple countries, including Argentina, Canada, Cape Verde, Denmark, Germany, the Netherlands, the Philippines, Singapore, South Africa, Spain, Switzerland, the United Kingdom and the United States.

Other passengers were from Australia, Belgium, France, Greece, Guatemala, India, Ireland, Japan, Montenegro, New Zealand, Poland, Russia, Turkey, and Ukraine.

Has hantavirus ever been recorded in Nepal? Does it spread from person to person?

No confirmed human hantavirus cases have been recorded in Nepal so far. However, a Spanish traveller developed hantavirus pulmonary syndrome after returning from Nepal in 2017, according to a report published by the US Centres for Disease Control and Prevention.

Researchers suspected the infection may have been acquired during the traveller's stay in Nepal, as he reported exposure to rats and mice in lodges. The infection caused a life-threatening respiratory failure.

The WHO says that, although uncommon, limited human-to-human transmission of hantavirus pulmonary syndrome has been reported in community settings involving closed and prolonged contact with infected persons. However, only the Andes strain of hantavirus is known to spread between humans.

What do virologists and epidemiologists in Nepal say?

Although Nepal has not confirmed any cases so far, experts say the risk of a hantavirus outbreak in the coming days cannot be ruled out. Given global travel, the movement of people in and out of the country means the risk of outbreak exists everywhere.

“Today, a patient came to our hospital with a rat bite,” said Dr Sher Bahadur Pun, chief of Clinical Research unit at the Sukraraj Tropical and Infectious Disease Hospital, who is also a virologist. “Over a dozen rat bite cases occur every day in Nepal. Many people die from respiratory illnesses, including pneumonia. We don’t always know the exact cause.”

Studies on the presence of hantavirus in rats have not been conducted in Nepal.

Doctors at Dhulikhel Hospital said they have requested swab samples from pneumonia patients to test for possible hantavirus infection through the National Public Health Laboratory.

“If you ask me in two weeks about the presence of hantavirus in our country, I will be able to say with evidence,” said Dr Rajiv Shrestha, registrar at Kathmandu University. “ We have requested the National Public Health laboratory for samples for whole-genome sequencing. It takes two weeks for the results to come.”

Shrestha oversees infectious disease, antimicrobial resistance, drug & vaccine trials, metagenomics & whole-genome sequencing at Kathmandu University.

What are health officials doing?

Officials say they have held discussions with stakeholders about the risk of an outbreak and have begun preparations for testing.

They are also coordinating with the WHO country office in Nepal.

“We don’t have testing kits for hantavirus, as they are not readily available in the market,” said Dr Runa Jha, director at the National Public Health Laboratory. “We are in close contact with WHO officials. The WHO headquarters will supply reagents or assist in sending samples to WHO collaborating centres abroad.”

What are the symptoms after infection?

People infected with hantavirus experience headache, dizziness, chills, fever, muscle pain, and gastrointestinal problems, including nausea, vomiting, diarrhoea, and abdominal pain, followed by the sudden onset of respiratory distress and hypertension. Symptoms may occur from two to four weeks of exposure to the virus, but may occur as early as one week or as late as eight weeks.

Treatment

There is no specific cure, vaccine or antiviral treatment for hantavirus. Doctors provide only supportive care. Therefore early detection is essential.

What does the WHO say about the risk?

The UN health body has assessed the risk to the global population from the cruise ship outbreak as low.