Why experts say the cruise ship hantavirus outbreak is not another Covid
The outbreak aboard the Dutch-operated MV Hondius has drawn global attention after passengers infected with the rare Andes strain of hantavirus travelled across several countries, prompting contact tracing efforts in Europe, Africa and South America.
Health experts say the virus behaves very differently from Covid-19 and is far less contagious.
WHO chief Tedros Adhanom Ghebreyesus said on Thursday that five confirmed and three suspected cases had been reported so far, including the three deaths. Because the Andes strain can incubate for up to six weeks, he warned that “more cases may be reported”.
Even so, WHO emergency alert director Abdi Rahman Mahamud said he expected “a limited outbreak” provided “public health measures are implemented and solidarity shown across all countries”.
The comments came as another infected passenger landed in Europe from the ship, which is heading towards Tenerife in Spain's Canary Islands after being refused permission to dock in Cape Verde.
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Rare virus
Hantavirus is a rare disease usually spread by rodents and can cause severe respiratory illness, cardiac complications and haemorrhagic fever. There is no vaccine and no specific cure.
Most hantavirus strains are not transmitted between humans. The Andes strain – first identified in South America – is one of the few exceptions, though scientists say transmission requires unusually close contact.
Researchers say this is why comparisons with Covid-19 are misleading.
“It cannot be compared at all because they are not from the same viral families, they do not necessarily have the same modes of transmission, they do not have the same infection rates, and they are not equally infectious,” Anne Lavergne, head of the laboratory associated with the National Hantavirus Center at the Pasteur Institute of French Guiana, told RFI.
Lavergne said Covid-19 could spread rapidly through casual contact, whereas Andes hantavirus spreads much less efficiently.
“With Covid cases, one person could infect ten others,” she said. “With hantaviruses at their most contagious – as documented for Andes – one person can infect only two others, and even then only in very specific situations, such as close contact with patients or individuals who have developed symptoms and have very high viral loads.”
Health authorities continue to describe the overall risk of a pandemic as low despite the international nature of the outbreak.
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Tracing the source
Investigators are still trying to determine where the outbreak began.
Authorities in Argentina believe a Dutch passenger contracted the virus before boarding the MV Hondius in Ushuaia on 1 April. The man died aboard the vessel on 11 April. His wife later died in South Africa after also testing positive.
Argentine officials said the couple had travelled extensively across South America after arriving in Argentina in November last year, including visits to Chile and Uruguay before returning to Buenos Aires to join the cruise.
On Thursday, Argentina's health ministry said “it is not possible to confirm the source of the infection” based on the information currently available from the countries involved.
The uncertainty has complicated efforts to identify where the original exposure took place.
Authorities consider it unlikely the couple became infected in Ushuaia because no hantavirus cases have been recorded there in three decades. Scientists are nevertheless being sent to Tierra del Fuego to retrace the couple's movements and capture rodents for testing.
The mission will look for a “possible presence of the virus” among local rodent populations, which are the primary carriers of hantavirus.
Argentina, where the disease is endemic in some Andean regions, has also distributed 2,500 testing kits to countries involved in the outbreak response, including the Netherlands, Spain, Britain, Senegal and South Africa.
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Cross-border tracking
The international dimension of the outbreak has increased concern among health authorities.
Passengers and crew from the Hondius disembarked at several locations during the voyage, including Saint Helena, where nearly 30 passengers left the ship.
WHO officials said 12 countries had been alerted that their nationals had travelled aboard the vessel.
One infected passenger flew commercially from Saint Helena to Johannesburg while symptomatic, leading South African authorities to trace 82 passengers and six crew members from the flight.
Confirmed or suspected cases are now being managed in Britain, Germany, the Netherlands, Switzerland and South Africa.
Oceanwide Expeditions, the company operating the ship, said there were currently no symptomatic passengers on board as it sails towards Tenerife.
Some passengers, however, have reportedly criticised what they see as exaggerated media coverage.
(with newswires)