Hantavirus: we'd better get used to it

The news of the appearance of an infectious outbreak of hantavirus on a luxury cruise ship in Atlantic waters has made headlines in all media and occupied large headlines. The memory of six years ago with the coronavirus pandemic has resurfaced. Words like isolation, quarantine or R0 have resonated. Are we back there again?

No. It is not the same, not by a long shot.

Hantavirus is a virus that is transmitted by the inhalation of particles from the feces and urine of infected rodents, which can cause hemorrhages or serious respiratory problems in humans and can even cause death. We distinguish between the Asian variants and the Andes variant, native to South America, which is more serious and the only one capable of being transmitted from person to person. This latter is what is affecting the passengers and crew of the cruise ship.

For a pandemic to appear – that is, an epidemic that affects a large territorial area – an infectious agent with high transmissibility and virulence, a susceptible population, and a relatively high density of people are required. Globalization and the ease of making long-distance international trips, along with favorable environmental conditions – often facilitated by climate change – help a pandemic to occur.

This is not the situation in this case. We have a poorly transmissible virus: the Andes hantavirus has a low R0 – basic reproduction number, which indicates the number of people an infected person can infect, on average – less than 1. For example, in COVID it was between 2 and 3, and in measles it is between 12 and 18. On the other hand, its person-to-person transmission is difficult, although in this case it is the most likely route of transmission. The susceptible population is high, because there is practically no prior immunity or vaccine, but, in this situation, it can only affect people who are on the ship. It is, therefore, limited. Certainly, the lethality is high, around 30%-40%, and the incubation period is long, between one and three weeks, although it can be up to seven weeks, which makes early identification difficult. Despite everything, the risk of a pandemic in our country in relation to this case is low. The WHO has not even declared a public health emergency of international concern. It is a serious problem, but localized and controlled. Nevertheless, for the crew and passengers of the ship, the risk is significant.

However: we had better get used to these kinds of alerts. There will be more and more of them.

This type of infection, frequently produced by viruses and transmitted by animals –zoonoses–, is increasingly on the rise. It is estimated that five new human diseases appear each year, three of which are of animal origin. 60% of infectious diseases affecting humans are of animal origin, and 70% of emerging diseases and almost all known pandemics are zoonotic. Climate change, changes in land use, agricultural expansion, urbanization, tourism, and contact with exotic animal species are at the root of this expansion. Add globalization and the high mobility of humans and goods, and we have the necessary ingredients for its spread. According to the journal Nature, in the next fifty years there will be 15,000 exchanges of viruses and parasites between animals and humans. 300 per year until 2070.

Unfortunately, this type of health crisis does not come alone. The situation of perceived crisis they generate involves extensive media coverage, amplified by digital networks. The infodemic emerges, a term popularized during the covid pandemic referring to the overabundance of information, which is generally not verified and can contribute to spreading false or self-serving information that can end up undermining the credibility of institutions and rigorous scientific information itself. The infectious outbreak transforms into a political weapon, with all the risks it entails.

Seeing the exchanges of accusations and fake news that have been broadcast in Spain in recent days regarding the possible transfer of the cruise ship and its passengers and crew –including the sick– to a port in the Canary Islands, it is evident that this outbreak is an example of all this.

Everyone must be clear that epidemic outbreaks and these kinds of diseases, while involving significant communicative and even political content, are not communicative or political problems: they are public health problems. This must be remembered. We had enough of this during covid six years ago.