The cruise ship at the center of a deadly outbreak of hantavirus has been refused permission to dock, with 149 people still on board — two of them seriously ill.

The virus is suspected to have killed three people and sickened three more, with one patient hospitalized in critical condition.

The World Health Organization said Monday that the ongoing risk to the general public from the disease — which is rare in humans and not easily transmitted — was low and there was no need for panic.

The remaining passengers, who are from 23 different countries, including 17 Americans, are being made to follow strict precautionary measures, including isolation and medical monitoring, the cruise operator said.

The west African nation of Cape Verde said it had decided not to let the cruise ship, the Hondius, dock at the port of Praia as a precautionary measure, Reuters reported.

The cruise operator, Oceanwide Expeditions, said in a statement Monday that the ship may sail from Cape Verde to Las Palmas or Tenerife in the Canary Islands and dock there.

One person, a British national, is in a hospital intensive care unit in Johannesburg, South Africa, that country's health ministry said in a statement. It said that the unidentified patient was in "critical condition."

So far this remains the one confirmed hantavirus case — the five others are suspected cases.

Two crew members, one British and one Dutch, were ill and required "urgent medical care" on board the Hondius, the cruise operator said. The WHO said it was assisting in planning the medical evacuation of these patients and an official from Cape Verde said an air ambulance was being prepared and would be used if needed.

Oceanwide said Sunday night that local health officials had been aboard to assess the two symptomatic people but were "yet to make a decision regarding the transfer of these individuals into medical care in Cape Verde."

The WHO stressed that there was no need for alarm.

"The risk to the wider public remains low. There is no need for panic or travel restrictions," WHO Regional Director for Europe, Dr Hans Henri P. Kluge, said in a statement Monday.

"We are acting with urgency to support the response to the hantavirus event on board a cruise vessel in the Atlantic, following the tragic loss of life," he said.

Kluge said he was in contact with authorities in Europe and South Africa to ensure a "science-based response."

The statement from Kluge also said that hantavirus infections can be "severe in some cases, if not easily transmitted between people."

A State Department spokesperson said on Monday that the government was closely watching the situation and stood "ready to provide consular assistance."

It remains unclear how passengers on the Hondius came to be infected, but Kluge said "infections are usually linked to exposure to infected rodents."

Two of the deceased victims were a married couple — a 70-year-old man who died on board on April 11 and was declared dead on arrival to the remote Atlantic island of St. Helena on April 24, and a 69-year-old woman who collapsed at Johannesburg’s international airport while attempting to fly back to the couple's native Netherlands.

Oceanwide said the third victim to die was a German national, although the official cause of death is not known.

The Hondius left Argentina for the Canary Islands, Spanish-controlled islands off the west coast of Africa, about three weeks ago, with around 150 passengers.

Kluge said the incident was an example of the need for international collaboration on health.

“Having just returned from the African continent, where I discussed closer collaboration on health emergencies, this is a timely reminder: health threats do not respect borders. Working together is how we protect people,” Kluge said.

President Donald Trump in January terminated U.S. membership of the WHO, citing alleged failures during the Covid-19 pandemic.

Hantavirus made headlines last year when a medical investigator confirmed it killed Betsy Arakawa, the wife of actor Gene Hackman, at the age of 65.