Understanding the Andes Hantavirus Transmission
Health officials have consistently indicated that close and sustained contact is essential for the spread of the Andes hantavirus, the one at the center of a recent outbreak on a cruise ship. Dr. Jay Bhattacharya, who serves as the acting director at the CDC, emphasized that the virus spreads primarily through close contact with symptomatic individuals.
However, researchers with extensive experience studying hantaviruses express some uncertainty regarding the virus’s behavior. While they concur that the Andes variant is not particularly contagious and unlikely to lead to substantial outbreaks, they also highlight that it can be transmitted without direct contact in certain situations.
Steven Bradfute, an expert in viral immunology at the University of New Mexico, stressed the importance of honest communication about the virus’s transmission methods to maintain credibility. Dr. Tedros Ghebreyesus, the World Health Organization director-general, acknowledged that health officials emphasize close contact to prevent unnecessary panic about more extraordinary transmission scenarios.
The outbreak that originated on the MV Hondius, a Dutch cruise ship, has reportedly made at least nine individuals ill, with three fatalities. Approximately 150 passengers are under close observation or in quarantine, especially 18 of them in the United States, who received specific instructions to monitor their health and limit interactions.
Dr. Bhattacharya mentioned in a CNN interview that some passengers who disembarked on April 24 didn’t exhibit symptoms during their travel, prompting officials not to alert the public or track potential contacts. He noted that the virus transmits only when individuals show active symptoms, yet the timing of contagion remains unclear. Some researchers suspect that people might be most contagious as they start showing symptoms.
Despite years of research, much is still unknown about hantaviruses due to their slow growth and genetic analysis challenges. They are typically found in rodents, and the Andes virus—primarily located in Argentina—has been established as the only hantavirus known to spread between humans, although this notion was once met with skepticism.
In a significant outbreak in Argentina between late 2018 and early 2019, research traced transmission through a group of 34 cases. The study confirmed that the virus is not easily transmitted; healthcare workers caring for infected individuals did not contract the virus, even without protective equipment. However, “super-spreading events” were identified, where one person infected multiple others at a birthday party shortly after developing symptoms.
Interestingly, not all cases involved direct contact with the ill; one individual likely caught the virus simply by saying hello to someone who was infected. Joseph G. Allen, director at Harvard’s Healthy Buildings program, noted that this kind of transmission doesn’t fit the close contact definition and indicated a more complex transmission dynamic could be at play.
Kartik Chandran, a virologist at Einstein College of Medicine, pointed out that the lack of data makes it challenging to draw definitive conclusions about transmission. Nevertheless, he and others argue that the low frequency of transmitted cases should reassure the public about the virus’s contagious nature. Dr. Tedros observed that after weeks aboard the ship, only a small fraction became infected, contrasting it with more contagious viruses like COVID-19.
There’s also mention of an infection linked to shared hospital space without direct contact, sparking speculation about airborne transmission possibilities. Linsey Marr, a virology expert, voiced frustration over reluctance to discuss inhalation routes in person-to-person transmission claims, suggesting it might be the simplest explanation for certain cases where direct interactions were absent.
Dr. Tedros noted that the WHO has not echoed this airborne transmission theory, citing the need for further study and data replication. However, researcher Gustavo Palacios contended that understanding the limits of the Andes virus under certain transmission conditions is vital for public health guidance.
In the U.S., the CDC took nearly a month to issue any statements regarding the outbreak. The agency continues to maintain that transmission requires close or intimate contact, referencing a general six-foot guideline drawn from COVID-19 precautions. Notably, there’s been some miscommunication among health officials regarding the initial deaths from the virus, including details that were inaccurately conveyed on television.
Interestingly, the third deceased individual in this case wasn’t closely related to the others, although she may have shared spaces with them. While officials from the Department of Health and Human Services insist that agencies have been active from the start, questions about the criteria for distance measures and statements made earlier remain unresolved.
The WHO has not issued specific distance recommendations like the CDC, highlighting the ongoing need for data and cooperation in understanding the evolving nature of this virus. Dr. Van Kerkhove emphasized the importance of continuing to learn about the virus as health officials work to assess the situation comprehensively.
