Salvador Peiró
Epidemiologist, researcher in the Health Services and Pharmacoepidemiology Research Area of the Foundation for the Promotion of Health and Biomedical Research of the Valencian Community (FISABIO) and Director of Gaceta Sanitaria, the scientific journal of the Spanish Society of Public Health and Health Administration (SESPAS)
Hantaviruses are not a new virus (they have been known since the 1950s – I believe since the Korean War – and were identified in the 1970s). It is not a virus that spreads through community transmission (it has nothing to do with covid-19) and is not transmitted between people (it could happen in certain circumstances, but it is very unlikely).
It is a zoonosis. It circulates commonly in mice (and voles and similar animals; these are its natural reservoir) and can infect humans when particles (usually dust) contaminated with their urine or faeces are inhaled.
There are two variants. In Europe, the most common is the Puumala virus, a hantavirus that typically causes symptoms including fever and kidney involvement, rarely severe and which, in many cases, go unnoticed. In South America, the variant is more aggressive and causes a cardiopulmonary syndrome with rapid respiratory failure, haemorrhages and a significant mortality rate.
It is a rare zoonosis that usually results in isolated cases in rural areas (or among hikers in rural areas). The outbreak on the cruise ship is striking due to the context (a cruise ship with several cases) and the severity (suggesting the South American hantavirus; also the origin of the cruise).
The large number of passengers suggests a common source of exposure: either before boarding the ship (the hantavirus has an incubation period of 2–4 weeks between infection and the onset of symptoms) or in some area of the ship contaminated by mouse droppings.
There is no general risk to the population wherever the ship goes. Passengers will need to be monitored for as long as it takes for symptoms to develop (not because they might infect others, but in case they fall ill) and the ship will need to be cleaned and treated for rodents.