The outbreak of hantavirus detected aboard the MV Hondius has once again placed zoonoses —diseases that jump from animals to humans— at the center of international health debate. Although experts rule out, for now, any real parallelism with the COVID-19 pandemic and lower the risk of a similar global expansion, the episode has served to reopen a fundamental discussion: to what extent is the world prepared to face biological threats increasingly conditioned by climate change, pressure on ecosystems, and growing interaction between humans and wildlife. Because if there is one thing the last decade has made clear, it is that the major health alerts of the 21st century no longer come only from hospitals, but also from the balance —or imbalance— between human, animal, and environmental health.
A serious virus, but not comparable
In statements to Demócrata, Dr. Javier Castrodeza Sanz, professor of Preventive Medicine and Public Health (University of Valladolid) and head of the Preventive Medicine and Public Health Service at the Hospital Clínico Universitario de Valladolid, explains the reasons why he does not consider it plausible that hantavirus will lead to a new pandemic, as happened with coronavirus.
Castrodeza argues that “hantavirus is not as transmissible as SARS-CoV-2 because, in general, it is not adapted to transmit efficiently from person to person through everyday respiratory routes”; but rather that “its transmission usually depends on specific environmental exposures, especially contact with or inhalation of aerosols contaminated with rodent urine, feces, or saliva”.
Remember that “COVID-19 spread with great efficacy because SARS-CoV-2 replicated in the upper respiratory tract and could be emitted into the environment by breathing, talking, or coughing, even with mild symptoms or before the person knew they were infected,” while hantavirus “does not circulate among humans and requires much more specific exposures.”
Ultimately, "hantavirus can cause severe conditions, but severity does not equate to transmissibility," which is why "its pandemic potential is much lower than that of a human respiratory virus with effective presymptomatic transmission, like SARS-CoV-2."
What are zoonotic diseases
Zoonotic diseases, or zoonoses, are infections that are transmitted from animals to people. They can spread through direct contact with infected animals, through contaminated food or water, or through vectors such as mosquitoes and ticks. Among the best-known zoonoses are rabies, salmonellosis, or COVID-19. Hantavirus, therefore, is also a zoonotic disease.
The real problem: when a zoonosis stops being local
In the opinion of Dr. Javier Castrodeza, zoonotic diseases constitute one of the greatest challenges for current and future public health crises, although they will not be the only ones. “Not all zoonoses have pandemic potential, but many of the threats with the greatest capacity to generate health emergencies come from the animal-human-environment interface,” he emphasizes.
Zoonoses appear where wildlife, domestic animals, livestock, vectors, people and ecosystems interact. “That is why it is not enough to monitor health events only in people and in their care space, health centers, hospitals etc.… it is also necessary to monitor animals, livestock farms, markets, wildlife, water, vectors and environmental changes,” points out Castrodeza.
The professor of Preventive Medicine and Public Health underlines that risk factors are increasing due to issues such as deforestation, land-use change, agricultural and livestock expansion, wildlife trade, rapid urbanization, climate change, international mobility, intensification of animal production, and biodiversity loss: “They favor new zoonotic jumps”.
"Not all zoonoses have pandemic potential, but many of the threats with the greatest capacity to generate health emergencies come from the animal-human-environment interface"
Filters that a zoonosis must overcome to cause a major crisis:
- Jump from animal to human.
- Effectively infect human cells.
- Be transmitted between people.
- Do so in a sustained manner.
- Spread before being detected or controlled.
A local event can go global
This expert explains that current connectivity fosters the spread of infections that were previously limited to a specific farm, village, or region; and COVID-10 was "the most extreme example," but there are also other processes such as avian flu, Ebola, monkeypox, and arboviruses "about which there is international concern."
In this regard, he points out that “in public health, it is not only lethality that is a concern, but the combination of transmissibility, severity, absence of prior immunity, diagnostic capacity, availability of vaccines or treatments, social trust, and response capacity”.
What are the especially concerning zoonoses
Especially concerning zoonoses:
- Those with efficient respiratory transmission, such as coronavirus or flu.
- Those that have broad and difficult-to-eradicate animal reservoirs.
- Those that mutate or recombine easily, such as flu.
- Those transmitted by vectors, sensitive to climate and ecological changes.
- Those with high lethality, such as Ebola or Nipah.
- Those that can be transmitted silently or presymptomatically.
- Those that simultaneously affect human health, animal health, the economy, and food security.
The scientific consensus is increasingly clear: zoonoses will mark a good part of the health threats of the 21st century. Recent experience has shown that the response involves consolidating a true One Health approach, capable of integrating epidemiological surveillance in humans, animals, and the environment, strengthening early detection, and streamlining information exchange between countries and health authorities. Added to this is the need to accelerate the development of vaccines, antivirals, and other response tools. In an increasingly interconnected world exposed to climatic and ecological changes, prevention is no longer just a health issue: it is also a strategic issue.