90-Second Read: What is Hantavirus, and why will cruise passengers spend so long in quarantine?

The Hantavirus outbreak aboard MV Hondius was "an example of inter-species disease transmission which has put health and government authorities on alert", said Dr Ariful Islam, an epidemiologist at Charles Sturt University who specialises in biosecurity and pandemic science. The current public health risk from Hantavirus remains low." Islam said it was important to be mindful that the next pandemic could be around the corner but, while the Hantavirus outbreak was alarming, people need not panic. After they arrive in Australia, the passengers who were aboard MV Hondius will spend the first three weeks of a 42-day quarantine at the Centre for National Resilience in Perth. The World Health Organization has recommended, but not mandated, a 42-day quarantine period. Four Australians, one permanent resident and one New Zealand citizen are.

Given the Covid-style quarantine of the returning passengers, how concerned should we be? Associate Prof Vinod Balasubramaniam, a molecular virologist at Monash University Malaysia, said Hantaviruses "do not usually spread easily from person to person in the way that you see flu or Covid-19 does". The most common type in South America is the Andes virus, which is also the virus responsible for the cruise ship outbreak. There are two major lineages of Hantavirus: old world Hantaviruses and new world Hantaviruses. New world Hantaviruses are found in the Americas and usually cause Hantavirus pulmonary syndrome.

Hantaviruses are usually spread to humans through contact with or inhalation of contaminated rodent faeces, urine and saliva. Unusually for Hantaviruses, human-to-human spread of the Andes virus has previously been documented. It's not a new virus … it's a known virus with many subtypes," said Islam, who researches the genetic diversity of Hantaviruses and their spillover risk to humans. Fatality rates from new world Hantaviruses, which cause more severe symptoms, tend to be much higher than deaths caused by the old world Hantaviruses. The facility was one of three built in response to the Covid-19 pandemic "to support the return of overseas travellers".

Old world Hantaviruses are found in Europe and Asia, these include puumala Hantavirus, Hantaan virus and Seoul virus. The new world Hantaviruses cause Hantavirus pulmonary syndrome, which has a fatality rate of about 40% in the Americas. This is not another Covid," Tedros Adhanom Ghebreyesus, the director general of the World Health Organization, said on Saturday. We know the history of host and transmission, we know the symptoms." It was "likely not possible" for the current outbreak "to become a full-blown pandemic similar to Covid-19 or H1N1, the previous flu pandemic", Balasubramaniam said. The concern here is not that Hantavirus is going to become like Covid or influenza." More concerning, he said, was the illness's high mortality rate.