Several people have died – but how dangerous is hantavirus really?
There are several variants of hantavirus. The South American one can be fatal.
Health workers in protective gear evacuating patients from the cruise ship MV Hondius in Cape Verde on Wednesday 6 May.(Photo: Misper Apawu / AP Photo / NTB)
Seven cases of hantavirus – with two others suspected, according to the World Health Organization (WHO) – linked to the cruise ship MV Hondius have so far been confirmed, the BBC writes in its latest
update.
Three passengers have died, and some have mild symptoms, while others
are critically ill.
"For Norway, the outbreak is primarily a
reminder that hantavirus is a group of viruses that can cause very serious illness," says Øverbø.
One affects the kidneys, the other the lungs
There are two types of hantavirus, says Jörn Klein, a professor of microbiology and infectious
disease control at the University of South-Eastern Norway.
The two are divided according to their disease symptom profile.
One of them affects the kidneys.
The other affects the lungs.
Most hantaviruses are not transmitted from person to person, with one exception – the Andes virus.
"In this case, limited transmission between people has been documented, especially through close and prolonged contact," says Øverbø from the Norwegian Institute of Public Health.
Infected before departure?
Both South African and Swiss authorities have both confirmed that they identified the Andes virus in the affected passengers. This type is primarily found in Argentina and Chile.
The hantavirus led to 28 deaths in Argentina last year, writes the AP news agency. And it was from Argentina that the cruise ship MV Hondius set sail on 1 April of this year.
Annonse
The prevailing theory is that someone was infected with the Andes virus before they boarded the ship.
The BBC writes that Argentinian officials believe the Dutch couple may have been infected during a birdwatching trip before they boarded the ship. The trip is said to have included a stop at a landfill where they may have been exposed to virus-carrying rodents.
"Another possibility is shared environmental exposure, such as contact with rodents or rodent-contaminated material during the journey or before departure," says Øverbø.
"A third possibility is limited transmission between people," says Øverbø. "For now, we have to wait for the final species determination and infection tracing before we can conclude the cause and route of transmission."
Drone image of the cruise ship MV Hondius as the luxury vessel sails from Cape Verde towards the Canary Islands on Wednesday.(Photo: Stringer / REUTERS / NTB)
Close and prolonged contact
The ship, which carried around 150 passengers, had been stranded off Cape Verde, before making its way to Tenerife so that passengers could be evacuated.
"A cruise ship could theoretically provide more opportunities for transmission between people than sparsely populated areas where previous outbreaks of this virus have been documented," says Øverbø.
But he emphasises that the Andes virus is not transmitted like the flu or Covid-19.
"The crucial factor seems to be close and often prolonged contact, not just being on the same ship," he says.
Suddenly very ill
Illness caused by the Andes virus starts with non-specific symptoms, Øverbø explains. Those who are infected may develop a fever, headache and muscle pain, nausea, vomiting, or stomach problems.
In some people, the illness progresses after a few days into a serious phase with coughing, difficulty breathing, fluid in the lungs, low blood pressure, and shock.
"This rapid transition from a flu-like or gastrointestinal onset to severe pulmonary and circulatory failure is what makes the Andes virus and other American hantaviruses dangerous," says Øverbø.
Health workers escort a patient, second from the right, after being evacuated from the ship MV Hondius to Schiphol Airport in Amsterdam.(Photo: Peter Dejong / AP Photo / NTB)
Puumala variant is only transmitted by rodents
The hantavirus found in Norway is something quite different. It is caused by a hantavirus called Puumala virus.
The Puumula virus is only transmitted by rodents and not between people.
"There is no reason to be afraid of normal social contact with a person who has had the Puumula virus," says Øverbø.
The disease can cause fever, headache, and back or stomach pains. Some people also develop acute kidney damage.
"Most people recover completely from the Puumala virus," says infectious disease expert Jörn Klein.
However, no
medicine is available for either the Andes or Puumala strain of the virus.
"Treatment consists of supportive measures, like supplemental oxygen. Beyond that, the body has to cope with it on its own," says Klein.
No one needs to be afraid of contracting one of the dangerous hantaviruses in Norway, the professor emphasises.
"People in Europe should be far more worried about the Puumala virus than the South American variant," he says.
Goes under the radar in Norway
Klein believes that illness caused by the Puumala virus is underdiagnosed in Norway.
"If we look at Swedish figures, they are sky-high, especially after winter when people clean out their cabins and woodsheds. In Norway, the numbers are low. But this virus doesn't stop at the border," he says.
According to Klein, around 10 per cent of those infected with the Puumala virus develop serious kidney symptoms and need dialysis.
Mild winters lead to more rodents
According to Klein, the cases of
hantavirus infection have seen a global increase as a result of global warming.
"Milder winters lead to larger rodent populations. I am not aware of any studies on this in Norway, but there is an increase globally," he says.
Øverbø believes the picture is a bit more complex.
"It is not a simple and unambiguous global increase.
Incidence varies from year to year. It's impacted by rodent populations, climate,
ecology, and human activity, but also by diagnostics and monitoring," he says.
Several thousand cases are reported each year in Europe, especially
from northern and central Europe, according to Øverbø.
In Asia, especially China and South Korea, the infection manifests as renal syndrome in many cases, but the incidence has decreased in recent decades.
In America, the cases of the severe pulmonary form are few, but it has a higher mortality rate.
In Africa, things are more uncertain.
"We know that hantaviruses exists there, but we know
less about how often they actually causes illness in humans," he says.
The disadvantage of cruise ships is that they are closed environments that you
cannot get away from, he says. Viruses can be spread through the ventilation system – not hantavirus, mind you, but influenza, for example.
Fortunately, it
is easy to isolate affected passengers on a ship and screen them for viruses.
"We know that cruise ships can be infection environments. There is often a large proportion of older passengers, so it's important to have good infection control measures in place on these ships," says the professor.
Hand hygiene is
extra important for anyone on holiday on a cruise ship.
"Get vaccinated and wash your hands," advises Klein. "Avoid public areas if you become ill and wear a face mask if you are in close contact with others, especially if you have a compromised immune system."
