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

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 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 World Health Organization has recommended, but not mandated, a 42-day quarantine period.

Hantaviruses are usually spread to humans through contact with or inhalation of contaminated rodent faeces, urine and saliva. There are two major lineages of Hantavirus: old world Hantaviruses and new world Hantaviruses. The most common type in South America is the Andes virus, which is also the virus responsible for the cruise ship outbreak. The facility was one of three built in response to the Covid-19 pandemic "to support the return of overseas travellers".

New world Hantaviruses are found in the Americas and usually cause Hantavirus pulmonary syndrome. Unusually for Hantaviruses, human-to-human spread of the Andes virus has previously been documented. Old world Hantaviruses are found in Europe and Asia, these include puumala Hantavirus, Hantaan virus and Seoul virus. Fatality rates from new world Hantaviruses, which cause more severe symptoms, tend to be much higher than deaths caused by the old world Hantaviruses.

There is no specific antiviral drug to treat such viruses, which are typically managed with supportive care, including oxygen, fluid management, blood pressure support and ventilation. This is due to the virus's long incubation period, the gap between initial exposure and when symptoms first develop.