Health authorities and scientists are closely monitoring an outbreak linked to the Andes hantavirus strain after cases emerged among passengers aboard a cruise ship carrying 149 people.
Several passengers have died, while others have been infected and are either in isolation or receiving hospital treatment because of more severe symptoms.
The outbreak has drawn international scientific attention not because of the number of confirmed cases, which remained limited as of Thursday, but because the strain involved is the only known hantavirus with documented human-to-human transmission.
Konstantinos Tsioutis, scientific coordinator of the European Committee on Infection Control, said the Andes strain differed from previous hantavirus outbreaks because it could spread between people under certain conditions.
He said the virus did not spread easily and was not comparable to COVID-19 or other respiratory viruses that move rapidly through communities.
Tsioutis said one reason for the heightened international response was the virus’s long incubation period, with symptoms potentially appearing up to 50 days after exposure.
He said infected people could travel normally for weeks before realising they were ill, making contact tracing and efforts to contain transmission significantly more difficult.
“The longer the incubation period, the harder it becomes to identify all possible contacts of a case,” he said, adding that health authorities were therefore monitoring the situation closely.
A second concern relates to the severity of the illness caused by the Andes virus.
In some patients, the virus can lead to hantavirus pulmonary syndrome (HPS), a serious condition affecting mainly the lungs and heart that can deteriorate rapidly.
HPS can cause severe breathing difficulties, fluid in the lungs, low blood pressure and, in severe cases, the need for mechanical breathing support.
According to epidemiological analyses so far, the initial exposure to the virus appears to have occurred before passengers boarded the MV Hondius cruise ship.
International health bodies, including the World Health Organization and the European Centre for Disease Prevention and Control, believe the outbreak may be linked to a birdwatching excursion in Argentina’s Patagonia region, where the Andes hantavirus is endemic.
Argentine authorities have already launched extensive rodent testing and sampling operations in the area, which is considered the likely source of the initial exposure.
The leading scenario under investigation is that limited transmission later occurred between passengers during the voyage.
According to available data, around 40 passengers disembarked before the first cases were identified on Saint Helena. Those passengers are now being traced, with some already located in their home countries or elsewhere and placed under monitoring by health authorities.
International news agencies reported that the epidemiological investigation now extends beyond cruise passengers and includes airline passengers, flight crews, close family contacts and healthcare workers who may have been exposed to possible cases.
By Thursday afternoon, 12 countries had activated special monitoring, isolation and medical assessment protocols.
Most hantaviruses spread only from rodents to humans through contact with infected animals’ urine, faeces or saliva.
The Andes strain is an exception. Tsioutis said human-to-human transmission had mainly been documented in cases involving very close and prolonged contact.
This typically includes people living in the same household, partners, carers and healthcare workers without adequate protective equipment.
Transmission appears to be linked to exposure to bodily fluids or prolonged time spent in enclosed spaces with symptomatic patients.
Tsioutis said the virus was not easily transmitted through brief social encounters or short periods spent in the same space.
The ECDC has also said there is currently no evidence of widespread or sustained community transmission.
Early symptoms can resemble flu or a common viral infection and may include fever, headache, severe muscle pain, fatigue, back pain, nausea, vomiting, diarrhoea, cough and chest pain.
More severe cases may involve shortness of breath, acute respiratory distress, fluid in the lungs, low blood pressure and shock.
There is currently no approved vaccine or specific antiviral treatment for the virus.
Treatment is based mainly on early diagnosis and supportive care, particularly for patients with severe respiratory complications.
Health experts advised the public to avoid contact with wild rodents and their droppings, ventilate enclosed spaces before cleaning them, use gloves and disinfectants in areas where rodents may be present, and avoid close contact with people showing suspicious symptoms and a relevant exposure history.
Experts stressed that the situation required caution rather than panic.
Tsioutis also warned about the spread of misinformation and conspiracy theories during international health incidents.
He said rapidly developing situations with unknown elements often led people to search for explanations, creating space for false information.
The ECDC has advised the public to rely only on official sources of information, including the ECDC, the World Health Organization, the US Centers for Disease Control and Prevention and national public health authorities.
The outbreak has triggered international concern because the Andes strain is the only known hantavirus capable of spreading between humans, while some passengers have still not been traced and questions remain about transmission among confirmed cases.
