The international health authorities are on high alert after a hantavirus infection occurred on the cruise ship "MV Hondius," which departed from Argentina and was crossing the Atlantic Ocean, resulting in fatalities.

Some experts have raised the possibility of the South American "Andes virus," suggesting the potential for limited human-to-human transmission. However, there is also analysis that joint exposure or environmental infection cannot be ruled out at this stage.

According to the World Health Organization (WHO), the infections occurred between April 6 and April 28. So far, there have been two confirmed cases and five suspected cases, with three fatalities among them. The first patient had stayed in Argentina just before departure, and a female close contact also died afterward.

Microscopic image of liver tissue from a patient with Hantavirus Pulmonary Syndrome (HPS) from an undated photo obtained by Reuters on July 6, 2017 (local time). Photo by Reuters Yonhap News

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Hantavirus is mainly transmitted through the droppings, saliva, and urine of rodents. In particular, when the droppings dry out and become airborne as fine particles, infection can occur via the respiratory tract. Human-to-human transmission is known to be extremely rare, but in the case of the Andes virus in South America, limited cases have been reported.

Professor Jeong Jaehoon from the Department of Preventive Medicine at Korea University College of Medicine explained to the Korea Science and Technology Media Center (SMCK), "The first fatality's history of staying in Argentina and the absence of rodents found on board suggest the possibility of the Andes virus. However, at this stage, it is important to be extremely cautious before concluding direct human-to-human transmission."

Experts believe that the key issue in this event is not merely whether infection occurred, but rather "identifying the transmission route." In the closed environment of a ship, what appears to be human-to-human transmission may actually be due to joint exposure or environmental contamination.

Professor Jeong said, "Indirect infection is entirely possible through exposure to the same food ingredients or storage spaces, circulation of contaminated particles in the ventilation system, or shared bedding and towels. It is extremely difficult to distinguish between environmental exposure and direct transmission from an epidemiological perspective."

Professor Benjamin Brennan of the Virus Research Centre at the University of Glasgow, UK, also stated, "Currently, WHO is considering a mixed scenario involving exposure to rodents and limited human-to-human transmission, but a definitive conclusion will only be possible after epidemiological and genomic analyses are completed."

Experts particularly emphasize that whether or not the Andes virus is involved is the key variable in interpreting this incident. Dr. Cesar Lopez-Camacho of the Jenner Institute at the University of Oxford noted, "For most hantavirus cases, environmental exposure is the primary suspicion, but if it is the Andes virus, human-to-human transmission must also be considered. Rapid diagnosis, genomic analysis, and epidemiological investigation must proceed simultaneously."

Research scientist Robert Nophchishi prepared inactivated substance samples as part of hantavirus research at the Global Health Center of the University of New Mexico Health Sciences Center in Albuquerque, New Mexico, on the 4th (local time). Photo by AP Yonhap News Agency

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Experts believe that the likelihood of this incident developing into a large-scale pandemic like COVID-19 is low. This is because hantavirus is not an airborne virus by nature, and cases of human-to-human transmission are extremely limited.

Amos Garcia Rojas, an epidemiology expert formerly with the Canary Islands health authorities in Spain, explained, "It is completely different from airborne viruses like COVID-19. Even with the Andes virus, reports of human-to-human infection are very rare, and only in cases of extremely close and prolonged contact."

However, the fatality rate is quite high. According to experts, the fatality rate for the Andes virus is about 40%, and for Hemorrhagic Fever with Renal Syndrome (HFRS) caused by Hantaan virus and Seoul virus, which occurs in Korea, the fatality rate also exceeds 5%.

Most importantly, there is no specific antiviral treatment for hantavirus, so early diagnosis and intensive care are crucial for survival. The initial symptoms often resemble those of a common cold, such as fever and muscle pain, but the condition can rapidly worsen into acute respiratory distress syndrome (ARDS) or multiple organ failure.

Korea is also not free from hantavirus. In 1976, Professor Ho Wang Lee was the first in the world to isolate the "Hantaan virus" from striped field mice near the Hantan River, and even now, 300 to 400 cases of Hemorrhagic Fever with Renal Syndrome occur annually in Korea.

Professor Jeong Jaehoon stated, "This incident should serve as an opportunity to raise awareness of hantavirus infection and strengthen early supportive care capabilities. In confined spaces, it is difficult to distinguish between direct transmission and joint exposure, so it is not possible to definitively conclude human-to-human infection at this stage."