This photo taken on May 21, 2023 shows a logo of the World Health Organization (WHO) with the WHO headquarters in the background in Geneva, Switzerland. (Xinhua/Lian Yi)

According to the WHO, seven individuals of the 147 passengers and crew have been reported ill and three have died. The situation remains fluid.

GENEVA, May 5 (Xinhua) -- Hantavirus victims on the ship Hundius in the Atlantic Ocean may have been infected prior to joining the cruise, and human-to-human transmission on board cannot be ruled out, the World Health Organization (WHO) said on Tuesday.

The agency received reports of a hantavirus outbreak on the Hundius on May 2. Seven individuals of the 147 passengers and crew have been reported ill and three have died. The situation remains fluid, WHO's chief of Epidemic and Pandemic Preparedness and Prevention Maria Van Kerkhove told reporters in Geneva.

"One patient is in intensive care in South Africa, although we understand that this patient is improving," she said, adding that two other patients, still on board the ship, are being prepared for medical evacuation to the Netherlands for treatment.

Van Kerkhove stressed that the situation is being closely monitored. As a precaution, passengers have been asked to remain in their cabins while disinfection and other public health measures are carried out.

"The plan is, and our highest priority is, to medically evacuate these two individuals" to make sure that they receive the required care, and there are no other symptomatic patients on board, she said.

The ship is set to continue on to the Canary Islands, Spain, and the WHO is working with the Spanish authorities "to do a full epidemiologic investigation, full disinfection of the ship," she added.

This file photo shows Maria van Kerkhove (R), who was technical lead for the WHO's Health Emergencies Program, speaking during a daily briefing in Geneva, Switzerland, on March 5, 2020. (Xinhua/Chen Junxia)

Hantaviruses are carried by rodents and can cause severe disease in humans. Thousands of infections are estimated to occur each year. People usually get infected through contact with infected rodents or their urine, their droppings, or their saliva.

As to the suspected origins of the virus, Van Kerkhove said that the initial patients -- a husband and wife -- boarded the ship in Argentina.

"With the timing of the incubation period of hantavirus, which can be anywhere from one to six weeks, our assumption is that they were infected off the ship," she said.

"We do believe that there may be some human-to-human transmission that's happening among the really close contacts," such as the husband and wife and others who have shared cabins, she noted.

According to the WHO, human-to-human transmission of infection hantavirus between people is uncommon, but limited spread has been reported among close contacts in previous outbreaks of the Andes virus, which is part of the hantavirus group.

There are no specific treatments for hantavirus other than supportive care. "Typically, people will develop respiratory symptoms, so respiratory support is really important," Van Kerkhove said.