What a 2018 Hantavirus Outbreak Revealed About Human-to-Human Spread... Beyond WHO’s ‘Prolonged Exposure’ Claim

The hantavirus outbreak linked to the Atlantic expedition cruise ship MV Hondius, which has so far infected several people and claimed three lives, is once again triggering memories of the early days of COVID-19. While doctors and infectious disease experts continue to stress that hantavirus does not have the capability to become a COVID-like global pandemic, what is now sparking debate is the way authorities are describing its transmission.

The World Health Organization has repeatedly maintained that hantavirus spreads only through 'very close and prolonged exposure' to an infected person. But that explanation is leaving some experts unconvinced. Some doctors and researchers are questioning what exactly qualifies as prolonged exposure, especially in light of findings from a detailed 2020 study published in the prestigious The New England Journal of Medicine that analysed a deadly hantavirus outbreak in Argentina. Dr Rajeev Jayadevan points out that the first two infections - the husband and wife - onboard the MV Hondius are understandable. According to current theories, the first victim may have contracted the virus before boarding the ship, developed symptoms later and then passed it on to his wife. "The proximity and intimacy explanation works there. But how did the others get infected? Did all of them really have very close, prolonged exposure to the first two cases?" he asks. The concerns become more interesting when one looks at the outbreak that WHO itself referenced: a 2018 hantavirus cluster in Argentina that later became the subject of the 2020 study. The outbreak took place between December 2018 and March 2019 in a small Andes town of around 2,400 residents where hantavirus is endemic. It eventually resulted in 34 infections and 11 deaths.According to the study’s lead co-author, Gustavo Palacios, the outbreak appears to have begun at a birthday party attended by around 100 guests. "It was a formal party with tables and about 100 people," Palacios explained. Patient 1 attended the gathering but stayed for only about 90 minutes because he had started feeling unwell and developed a fever. Within 17 to 24 days, five people who had been seated near him developed symptoms consistent with hantavirus pulmonary syndrome. There was also a sixth case linked to what appeared to be an extremely brief interaction. During contact tracing, researchers found that one individual had simply crossed paths with Patient 1 in the bathroom, where the two greeted each other.

The study then identified another attendee 'Patient 2' as the most likely source of six subsequent infections because of his active social life. Patient 2 died 16 days after symptoms began. During his wake, his spouse developed a fever. Soon after, another 10 people who attended the funeral and had close contact with a different infected individual, Patient 9, also fell ill between 14 and 40 days later. The remaining patients had all been in contact with at least one symptomatic individual.What makes the study especially significant is that it hinted at the possibility of 'super spreaders' and suggested that the threat posed by hantavirus may need to be reassessed. "The lack of approved medical treatments, the potential for widespread transmission, and the high case fatality rate of the infection should raise concerns," Palacios wrote in the paper.This is exactly why some experts now wonder whether discussions around hantavirus transmission are being framed too narrowly, particularly when transmission is described mainly in hospital or sexual-contact contexts. Palacios had offered a much broader definition of what his team considered close or high risk contact. "The one we used in this study, which was quite strict was a person who had been within one metre of an infected person for at least 30 minutes," he said. And that is where the debate now lies.If being in the same room, sitting nearby at a party, or briefly interacting in a bathroom could potentially lead to transmission in the Argentina outbreak, doctors say it becomes important to clearly define what health agencies mean when they reassure people that hantavirus spreads only through 'prolonged exposure.'No one is suggesting that hantavirus is the next COVID-19. Experts remain clear that its transmission dynamics are very different and far less efficient. But the questions being raised now are less about panic and more about precision in communication.