Human-to-human transmission of the rodent-borne hantavirus may be quite rare, but a deadly outbreak that happened on board a cruise ship in the Atlantic Ocean now has health officials around the world — including here in Canada — monitoring for any potential spread.
That includes carrying out contact tracing for individuals who may have come in close and prolonged contact with infected passengers from the MV Hondius, which left Argentina on April 1.
At least 30 MV Hondius passengers left the vessel when it docked at the South Atlantic island of St. Helena on April 24 and have since travelled onward or returned to their home countries.
It’s unclear whether any of those individuals were exposed to the virus, but health officials will need to track them down and, if they are infected, who else they may have come in contact with.
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Contract tracing is something that much of the global public became familiar with at the start of the COVID-19 pandemic in 2020.
Doctors and health officials have stressed that the hantavirus outbreak is not remotely similar in scale and the risk to the greater public is low.
But now that the World Health Organization (WHO) confirmed the outbreak is connected the Andes strain of hantavirus, which is endemic to Argentina and is the only strain known to spread from human to human, there is a need for a co-ordinated response to track potential spread.
“Given the incubation period of the Andes virus, which can be up to six weeks, it’s possible that more cases may be reported,” WHO director-general Dr. Tedros Adhanom Ghebreyesus said.
Here’s what you should know about the efforts to track and contain the potential spread of the hantavirus.
World Health Organization director-general Tedros Adhanom Ghebreyesus said Thursday his organization will work alongside a cruise ship operator and governments after cases of hantavirus were reported among passengers. Medical teams, he said, will take care of patients and work to ‘prevent onward spread of the virus.’
Why is it important to trace contacts?
Contact tracing is about identifying, informing and monitoring people who might have come in contact with a person who has been diagnosed with an infectious disease.
WHO released its first “disease-agnostic” contact tracing guidelines last year.
Contact tracing starts with identifying a person who has been exposed to an infectious disease or pathogen and, while taking the mode of possible transmission into consideration, tracking the people they may have been in close proximity with.
That could be in the same household, workplace or settings like cruise ships and passenger planes, as well as other environments that could increase the risk of exposure such as social gatherings or certain activities.
Those contacts are then monitored, either by self-reporting or by public health authorities, for evidence of infection.
But contact tracing can be complicated because of the nature of modern travel, Dr. Alfredo Mena Lora, an infectious diseases specialist at the University of Illinois college of medicine, told CBC News Network.
“It’s easy to go from one place to another and there’s a lot of people, sometimes, in a single place such as an airport or [on] a flight,” he said.
Another complicating factor, he said, is that hantavirus has a long incubation period, ranging from two to six weeks, before symptoms can show up.
“Through that tracing, we can kind of draw a tree and better understand who may be exposed and if [a] person, for example, develops symptoms.”
The cruise ship at the centre of a hantavirus outbreak is heading to the Canary Islands where its remaining passengers, including four Canadians, will disembark. None of those passengers currently have any symptoms.
Passenger manifests from the cruise ship and flights that disembarked passengers may have travelled on afterward will be helpful to health officials looking to reach out to potential contacts, said Dr. Anna Banerji, an infectious diseases and tropical diseases specialist at the University of Toronto’s Dalla Lana school of public health.
But it could still prove challenging, she said, if people aren’t showing any symptoms.
That’s why she said it’s also valuable to have people self-identify if they may have been on MV Hondius or may have been in close contact with someone who is infected.
How is it different from COVID-19 contact tracing?
Banerji said even though there were initial efforts to carry out contact tracing for COVID-19, the viral infection could be slowed down but ultimately couldn’t be contained.
COVID-19 is highly infectious and spread through sharing the same air as infected individuals. It has affected hundreds of millions of people around the world since the onset of the pandemic in 2020.
“This is nothing like COVID,” Banerji said.
Contact tracing in this situation, Banerji said, may be similar to outbreaks of diseases like tuberculosis and measles, which are also spread by prolonged and close contact.
“With measles,” she said, “they looked at who got sick, who is in their immediate family, who’s at risk [and] who’s not vaccinated.”
There is no vaccine or antiviral treatment for hantavirus, but Banerji said contact tracing would help determine who may need to isolate as a result of potential exposure to the virus.
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How many people are affected — and where are they?
At this point, there are five confirmed cases of the hantavirus among the MV Hondius passengers — including a German national and a Dutch man who died on the ship and a Dutch woman who later died at a hospital in Johannesburg.
Further suspected cases are being examined.
Four Canadians remain on board the vessel, along with more than 140 passengers and crew members from 23 countries, as it makes its way to Spain’s Canary Islands for evacuation, after spending days stranded off the coast of island country of Cape Verde.
None of the Canadians have experienced symptoms of the illness at this point in time, the Public Health Agency of Canada confirmed to CBC News.
Two other Canadians who disembarked the MV Hondius in St. Helena, along with 30 other passengers, are back in Canada and isolating at home in Ontario without symptoms.
An additional Canadian who was not a cruise ship passenger is also in isolation in Quebec after coming into contact with the pair from Ontario on the same flight home, Foreign Affairs Minister Anita Anand said Thursday.
Elsewhere, a symptomatic passenger from Switzerland is being treated at a hospital in Zurich. Two Singapore residents who were on the MV Hondius isolated at the country’s National Centre for Infectious Diseases but have since tested negative.
There is also a suspected case in the remote mid-Atlantic island of Tristan da Cuhna, where the ship stopped on April 15.
A flight attendant from Dutch airline KLM was investigated for hantavirus at an Amsterdam hospital after coming in contact with one of the Dutch woman but tested negative.
Infectious disease specialist Dr. Zain Chagla spoke with CBC Radio’s The Dose about the risk of hantavirus in Canada, and the difference between the two syndromes it can cause. Health authorities said Wednesday that the Andes strain of hantavirus has been identified on a cruise ship at the centre of a deadly outbreak.
