What the numbers tell us about hantavirus

By Jen Christensen, CNN

(CNN) — Health authorities across several countries are racing to trace and contain an outbreak of hantavirus after the World Health Organization said Thursday that five confirmed infections had been identified among people connected to the cruise ship MV Hondius.

The virus is typically associated with rodents, but it may have passed from human to human aboard the vessel, according to WHO. Since April 11, three people from the ship have died, while a handful of others are sick.

The outbreak was first reported to WHO on May 2 and remains a low risk to the general public, the organization says. Spanish authorities will conduct a full epidemiological investigation and disinfect the ship after it docks in Tenerife in the Canary Islands, where WHO believes the port has the right conditions for passengers to safely disembark.

Here are the details by the numbers so far.

How many people are potentially exposed?

• There were 147 people – 88 passengers and 59 crew members – aboard the MV Hondius, according to the World Health Organization.
• Those on board represent 23 nationalities, including 17 Americans.
• Authorities are completing additional contact tracing of 82 passengers and six crew members from an April 25 Airlink flight to Johannesburg from Saint Helena that a Dutch woman who had been on the ship took before she died.
• KLM said authorities in the Netherlands have also reached out to an undisclosed number of passengers on a second flight that the Dutch woman briefly boarded in Johannesburg. She left the 11:15 p.m. flight, KL592, before it took off because she was too sick to fly.
• Swiss authorities are carrying out additional contact tracing for people who came into contact with a passenger who left the MV Hondius in late April and is being treated at a Swiss hospital, according to Switzerland’s health ministry. The patient’s wife, who was also on the trip, has not reported symptoms and is isolating as a precaution, the Swiss health ministry said.
• In the US, the Department of State is in direct contact with passengers, and state departments of health are also involved. The Georgia Department of Public Health says it is monitoring two Georgia residents who returned home from the ship but have shown no signs of infection. An Arizona resident who was a passenger on the ship has not had symptoms and is being monitored by public health workers, according to the Arizona Department of Health. California, Texas, and Virginia are also monitoring passengers. None is exhibiting signs of the illness.
• Governments are also tracking at least 30 passengers who disembarked at the remote South Atlantic island of Saint Helena in late April, and others who went through other ports, leaving for a variety of countries, all before the outbreak was fully understood.

How many people have gotten sick?

• As of Thursday, there were five confirmed cases, and others are considered suspected cases, according to WHO.

What do we know about the people who died?

• Three people have died in connection with the illness cluster.
• On April 6, a 70-year-old Dutch man suddenly fell ill on the ship with a fever, headache, abdominal pain and diarrhea, according to the South African Health Department. He went into respiratory distress April 11 and died onboard the ship that day. No microbiological tests were performed to determine his illness. His body was removed to Saint Helena on April 24.
• On April 24, the man’s 69-year-old wife went ashore at Saint Helena with stomach problems. She then flew to Johannesburg, and her condition deteriorated on board, WHO said. She collapsed while trying to fly home to the Netherlands and died at a nearby hospital on April 26. On May 4, scientists used molecular tests to confirm that she had hantavirus.
• The third person to die, a German woman, came down with a fever and appeared to have pneumonia April 28. She died May 2 on board the ship. Her cause of death is not officially established, but it’s being treated as a suspected hantavirus case.

When did people get sick?

• According to WHO, the first passenger is believed to have developed symptoms April 6.
• The last person to develop symptoms got sick on April 28.

What’s happened to those who have gotten sick?

• The second person with a confirmed case first reported to the ship’s doctor on April 24. The man had a fever, shortness of breath and signs of pneumonia. On April 26, his condition deteriorated, and he was evacuated the next day to South Africa, where he remains in an intensive care unit. Initial lab tests for hantavirus were negative, but on May 2, a molecular test confirmed a hantavirus infection.
• A ship doctor is one of three people evacuated Wednesday, according to WHO chief Dr. Tedros Adhanom Ghebreyesus. Another is a person associated with one of the people who died. The three will be sent for care in the Netherlands.
• And two crew members — one British and one Dutch — have acute respiratory symptoms requiring urgent care, Oceanwide Expeditions said. Hantavirus has not been confirmed in either case.
• A seventh suspected case reported a mild fever but is now feeling well, WHO said. They have provided a sample for hantavirus testing.
• Another case emerged Wednesday when Swiss authorities confirmed that a man was being treated for hantavirus at University Hospital Zurich. After he developed symptoms, he asked his doctor what to do before going to the hospital for testing that determined he had the Andes strain of the hantavirus.

Who is caring for the passengers on the ship?

• Two specialist doctors from the Netherlands who arrived Wednesday and will remain with the vessel, the tour operator said.
• Another doctor is already on board.

Where is the ship?

• The ship left Cape Verde at 7:15 p.m. local time Wednesday and is heading north.
• The plan is for the MV Hondius to sail for the Canary Islands on a journey that takes three to four days, according to Oceanwide Expeditions.

Where will the rest of the passengers go once they are allowed to leave?

• Fourteen Spanish passengers on board will be transported to a military hospital after being examined.
• Other remaining passengers will be repatriated, according to Spain’s health minister, Mónica García.

Where did the virus came from?

• Authorities are still investigating the origins of the case cluster.
• WHO believes that the Dutch couple and possibly others were infected before they joined the cruise April 1, possibly while doing some activities in Argentina, where hantavirus is endemic, said Dr. Maria Van Kerkhove, WHO’s director for epidemic and pandemic preparedness and prevention.

What strain is the virus?

• After sequencing the virus from some of those infected, WHO confirmed that the cases were the result of a strain called the Andes hantavirus.
• The Andes strain is considered the only type of hantavirus known to have some limited human-to-human transmission.

How long does it take to show symptoms?

• Hantavirus typically incubates for one to six weeks after exposure.
• Patients can show symptoms as early as one week or as late as eight weeks after exposure, according to WHO.

How long will the exposed have to monitor for symptoms?

• WHO says passengers and crew should “remain vigilant” for hantavirus symptoms for 45 days.
• As a precaution, the European Centre for Disease Prevention and Control considers everyone on the ship to be close contacts due to the closed setting and shared activities.

How deadly is hantavirus?

• Hantavirus is a rare but extremely deadly virus.
• The hantavirus found in the Americas can cause hantavirus pulmonary syndrome. About 38% of people who develop respiratory symptoms may die, according to the CDC.
• There’s no vaccine that prevents hantavirus and no specific treatment for it.
• Early supportive care and immediate referral to a facility with a complete ICU can improve survival, according to WHO.
• WHO has classified hantaviruses in general as an emerging priority because of how serious the infections can be.

How contagious is it?

• Human‑to‑human transmission due to Andes virus is rare but has been reported in community settings involving close and prolonged contact, like among married couples and people who shared cabins, according to WHO. “This is not a virus that spreads like flu or like Covid. It’s quite different,” Van Kerkhove said.
• Dr. Gustavo Palacios, a microbiologist at the Icahn School of Medicine at Mount Sinai in New York who studied the virus in Argentina, estimated that there have been about 3,000 cases of the Andes strain of the virus in history.
• Palacios believes the window for transmission of the Andes virus is short, maybe about a day, but it can spread easily after someone is in only brief proximity to the person who is sick.
• Peak infectiousness is believed to be on the day a fever begins.
• According to Palacios’ study of a 2018-19 outbreak in Argentina, the Andes virus reproductive number was estimated at an average of 2.12, meaning each infected person passed the virus to about 2.12 other people before there were public health interventions. The overall outbreak average was 1.19. After interventions like isolation and quarantine, it was 0.96. It’s unclear what the reproductive number of the cruise ship cluster might be.

How many hantavirus cases have there been in the US?

• From 1993 to 2023, 890 cases of hantavirus disease were reported in the US, most of them in western states, CDC data shows.
• Interest in hantavirus spiked last year after Betsy Arakawa, wife of the Oscar-winning actor Gene Hackman, died of hantavirus at age 65.
• There have been an estimated 60,000 to 100,000 cases worldwide each year, with China accounting for about half of the cases, according to a 2024 study.

CNN’s Brenda Goodman contributed to this report.

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