Do Hantaviruses behave like COVID-19? What we know about the risk of transmission

According to the World Health Organization (WHO) and the European Centre for Disease Prevention and Control(ECDC), the epidemiological risk associated with Hantaviruses remains low and does not suggest scenarios comparable to those seen during the COVID-19 pandemic.

“The transmission dynamics are completely different from SARS-CoV-2,” emphasizes Professor Castagna. “We are not dealing with a virus characterized by high respiratory transmissibility within the general population.”

A crucial factor concerns the role of rodents as the natural reservoir of the virus. Each Hantavirus is associated with specific rodent or vole species, which carry the virus without developing clinically evident disease.

“Rodents coexist with the virus without showing symptoms,” explains the infectious disease specialist. “This makes them extremely efficient natural reservoirs, biologically very different from humans, who may instead develop severe clinical forms.”

Over the years, small epidemic clusters have been documented, generally associated with increased human exposure to infected rodents or their excreta. In most cases, however, transmission occurs directly from animals to humans.

Prevention remains the most effective strategy for reducing the risk of infection.

“One simple and important measure remains careful hand washing,” recalls Professor Castagna.

It is also essential to pay attention to environments potentially infested by rodents. In basements, storage areas, cabins, or enclosed rural environments where rodent droppings may be present, dry sweeping should be avoided because it may aerosolize contaminated particles. Instead, it is preferable to use detergents, damp cloths, and, when necessary, appropriate personal protective equipment during cleaning activities.

For healthcare personnel, suspected or confirmed cases must be managed according to specific isolation and biosafety protocols. The use of personal protective equipment (PPE), including gloves and masks, is recommended when caring for patients.

Suspected cases are generally referred to infectious disease reference centers, including Ospedale Luigi Sacco, IRCCS Policlinico San Matteo, and INMI Lazzaro Spallanzani.

Although the epidemiological risk is considered low, symptoms potentially compatible with Hantavirus infection should not be underestimated. Fever, respiratory symptoms, acute kidney injury, or hemorrhagic manifestations require prompt evaluation, especially in the presence of suggestive epidemiological history such as travel to endemic areas or contact with rodents.

The correlation between clinical symptoms and exposure history is essential for correctly guiding diagnostic suspicion.

One of the most relevant aspects of the Andes virus is its relatively long incubation period, which may reach up to 6 weeks.

“This means that close contacts of a confirmed case must be monitored over an extended period because symptoms may appear many days after exposure. In the early stages of infection, diagnostic tests may also be negative. Both PCR and serological tests may not become positive immediately; therefore, an adequate period of clinical observation is necessary,” continues the specialist.

Clinical severity varies significantly depending on the viral strain involved.

European Hantaviruses, such as Puumala and Dobrava-Belgrade viruses, generally have relatively low mortality rates. In the case of the Puumala virus, mortality is below 1%, while for Dobrava-Belgrade it may reach approximately 5%.

The situation differs for the Andes virus, which is associated with Hantavirus Pulmonary Syndrome (HPS), a more severe clinical condition. Mortality associated with the Andes virus may reach 30–40%, but the infection remains confined to specific areas of South America.

The natural reservoir of Hantaviruses consists of wild rodents. Each viral variant tends to be associated with a specific animal species.

The species involved vary according to geographic area:

• Andes virus: mainly associated with the rodent Oligoryzomys longicaudatus (long-tailed pygmy rice rat), widespread in South America;
• Puumala virus: associated with the bank vole (Myodes glareolus), found in Europe;
• Dobrava-Belgrade virus: associated with several species of the Apodemus genus (wild mice).

These ecological and geographic differences contribute to limiting the global spread of the various Hantaviruses.

“Not all rodents transmit the same Hantaviruses. The species present in Europe differ from those found in South America, just as the associated viruses differ. This ecological specificity is another major reason why experts consider a global spread comparable to COVID-19 unlikely, ” concludes Castagna.

Hantaviruses do not behave like SARS-CoV-2. The Andes virus, belonging to the Hantavirus family, and the coronavirus responsible for COVID-19 both share the possibility of human-to-human transmission, but with very different epidemiological characteristics.

“The contagiousness of COVID-19 was extremely high, whereas that of the Andes virus appears significantly lower. The outbreaks described in the literature showed limited and generally controllable spread,” explains Professor Castagna.

The modes of transmission also differ substantially:

• in the case of SARS-CoV-2, transmission occurs predominantly through airborne respiratory droplets and aerosols;
• in the case of Hantaviruses, the primary mode of infection remains contact with excreta from infected rodents (urine, feces, or saliva) or with aerosolized contaminated particles.

“It is important not to speak generically about Hantaviruses. Only the Andes virus has demonstrated documented human-to-human transmission, whereas the Hantaviruses circulating in Europe show no evidence of stable spread among humans,” the expert continues.

In Europe, the strains most frequently identified are the Puumala virus and the Dobrava-Belgrade virus, mainly responsible for hemorrhagic fever with renal syndrome (HFRS). To date, there is no scientific evidence of sustained human-to-human transmission for these viruses.